[Federal Register: October 4, 2004 (Volume 69, Number 191)]
[Proposed Rules]               
[Page 59305-59474]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr04oc04-28]                         
 

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Part II





Department of Labor





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Occupational Safety and Health Administration



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29 CFR Parts 1910, 1915, 1917, 1918, and 1926



Occupational Exposure to Hexavalent Chromium; Proposed Rule


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DEPARTMENT OF LABOR

Occupational Safety and Health Administration

29 CFR Parts 1910, 1915, 1917, 1918, and 1926

[Docket No. H054A]
RIN 1218-AB45

 
Occupational Exposure to Hexavalent Chromium

AGENCY: Occupational Safety and Health Administration (OSHA), 
Department of Labor.

ACTION: Proposed rule; request for comments and scheduling of informal 
public hearings.

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SUMMARY: The Occupational Safety and Health Administration (OSHA) 
proposes to amend its existing standard for employee exposure to 
hexavalent chromium (Cr(VI)). The basis for issuance of this proposal 
is a preliminary determination by the Assistant Secretary that 
employees exposed to Cr(VI) face a significant risk to their health at 
the current permissible exposure limit and that promulgating this 
proposed standard will substantially reduce that risk. The information 
gathered so far in this rulemaking indicates that employees exposed to 
Cr(VI) well below the current permissible exposure limit are at 
increased risk of developing lung cancer. Occupational exposures to 
Cr(VI) may also result in asthma, and damage to the nasal epithelia and 
skin.
    This document proposes an 8-hour time-weighted average permissible 
exposure limit of one microgram of Cr(VI) per cubic meter of air (1 mg/
m3) for all Cr(VI) compounds. OSHA also proposes other 
ancillary provisions for employee protection such as preferred methods 
for controlling exposure, respiratory protection, protective work 
clothing and equipment, hygiene areas and practices, medical 
surveillance, hazard communication, and recordkeeping. OSHA is 
proposing separate regulatory texts for general industry, construction, 
and shipyards in order to tailor requirements to the circumstances 
found in each of these sectors.

DATES: Written comments. The Agency invites interested persons to 
submit written comments regarding the proposed rule, including comments 
on the information collection determination described in Section X of 
the preamble (OMB Review under the Paperwork Reduction Act of 1995), by 
mail, facsimile, or electronically. All comments, whether submitted by 
mail, facsimile, or electronically through the Internet, must be sent 
by January 3, 2005.
    Informal public hearings. The Agency plans to hold an informal 
public hearing in Washington, DC, beginning on February 1, 2005. OSHA 
expects the hearing to last from 9:30 a.m. to 5:30 p.m.; however, the 
exact daily schedule is at the discretion of the presiding 
administrative law judge.
    Notice of intention to appear to provide testimony at the informal 
public hearing. Interested persons who intend to present testimony at 
the informal public hearing in Washington, DC, must notify OSHA of 
their intention to do so no later than December 3, 2004.
    Hearing testimony and documentary evidence. Interested persons who 
request more than 10 minutes to present their testimony, or who will be 
submitting documentary evidence at the hearing, must provide the Agency 
with copies of their full testimony and all documentary evidence they 
plan to present by January 3, 2005. See Section XVI below for details 
on the format and how to file a notice of intention to appear, submit 
documentary evidence at the hearing, and request an appropriate amount 
of time to present testimony.

ADDRESSES: Written comments. Interested persons may submit three copies 
of written comments to the Docket Office, Docket H054A, Room N-2625, 
OSHA, U.S. Department of Labor, 200 Constitution Avenue, NW., 
Washington, DC 20210; telephone (202) 693-2350. If written comments are 
10 pages or fewer, they may be faxed to the OSHA Docket Office, 
facsimile number (202) 693-1648. Comments may also be submitted 
electronically through the Internet at http://ecomments.osha.gov. 

Supplemental information such as studies and journal articles cannot be 
attached to electronic submissions. Instead, three copies of each 
study, article, or other supplemental document must be sent to the OSHA 
Docket Office at the address above. These materials must clearly 
identify the associated electronic comments to which they will be 
attached in the docket by the following information: Name of person 
submitting comments; date of comment submission; subject of comments; 
and docket number to which comments belong.
    Informal public hearings. The informal public hearing to be held in 
Washington, DC, will be held in the Frances Perkins Building, U.S. 
Department of Labor, 200 Constitution Avenue, NW., Washington, DC 
20210.
    Notice of intention to appear to provide testimony at the informal 
public hearing. Interested persons who intend to present testimony at 
the informal public hearing in Washington, DC, may submit three copies 
of their notice of intention to appear to the Docket Office, Docket 
H054A, Room N-2625, OSHA, U.S. Department of Labor, 200 Constitution 
Avenue, NW., Washington, DC 20210. Notices may also be submitted 
electronically through the Internet at http://ecomments.osha.gov. OSHA 

Docket Office and Department of Labor hours of operation are 8:15 a.m. 
to 4:45 p.m.
    Hearing testimony and documentary evidence. Interested persons who 
request more than 10 minutes in which to present their testimony, or 
who will be submitting documentary evidence at the informal public 
hearing must submit three copies of the testimony and the documentary 
evidence to the Docket Office, Docket H054A, Room N-2625, OSHA, U.S. 
Department of Labor, 200 Constitution Avenue, NW., Washington, DC 
20210. Written testimony may also be submitted electronically through 
the Internet at http://ecomments.osha.gov.

    Please note that security-related problems may result in 
significant delays in receiving comments and other materials by regular 
mail. Telephone the OSHA Docket Office at (202) 693-2350 for 
information regarding security procedures concerning delivery of 
materials by express delivery, hand delivery, and messenger service.
    All comments and submissions will be available for inspection and 
copying in the OSHA Docket Office at the address above. Most comments 
and submissions will be posted on OSHA's Web page (http://www.osha.gov
). Contact the OSHA Docket Office at (202) 693-2350 for 

information about materials not available on the OSHA Web page and for 
assistance in using this Web page to locate docket submissions. Because 
comments sent to the docket or to OSHA's Web page are available for 
public inspection, the Agency cautions interested parties against 
including in these comments personal information such as social 
security numbers and birth dates.

FOR FURTHER INFORMATION CONTACT: For general information and press 
inquiries, contact Mr. George Shaw, Office of Communications, Room N-
3647, OSHA, U.S. Department of Labor, 200 Constitution Avenue, NW., 
Washington, DC 20210; telephone (202) 693-1999. For technical 
inquiries, contact Ms. Amanda Edens, Directorate of Standards and 
Guidance, Room N-3718, OSHA, U.S. Department of Labor, 200 Constitution 
Avenue, NW., Washington, DC 20210; telephone (202) 693-2093 or

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fax (202) 693-1678. For hearing information contact Ms. Veneta Chatmon, 
Office of Communications, Room N-3647, OSHA, U.S. Department of Labor, 
200 Constitution Avenue, NW., Washington, DC 20210; telephone (202) 
693-1999.

SUPPLEMENTARY INFORMATION: For additional copies of this Federal 
Register document, contact the Office of Publications, Room N-3101, 
OSHA, U.S. Department of Labor, 200 Constitution Avenue, NW., 
Washington, DC 20210; telephone (202) 693-1888. Electronic copies of 
this Federal Register, as well as news releases and other relevant 
documents, are available at OSHA's Home page at http://www.osha.gov.


I. General

    The preamble to the proposed standard on occupational exposure to 
chromium (VI) discusses events leading to the proposal, health effects 
of exposure, the degree and significance of the risk presented, a 
summary of the analysis of technological and economic feasibility, 
regulatory impact, and regulatory flexibility, and the rationale behind 
the specific provisions set forth in the proposed standard. The 
discussion follows this outline:

I. General
II. Issues
III. Pertinent Legal Authority
IV. Events Leading to the Proposed Standards
V. Chemical Properties and Industrial Uses
VI. Health Effects
VII. Preliminary Quantitative Risk Assessment
VIII. Significance of Risk
IX. Summary of the Preliminary Economic Analysis and Initial 
Regulatory Flexibility Analysis
X. OMB Review under the Paperwork Reduction Act of 1995
XI. Federalism
XII. State Plans
XIII. Unfunded Mandates
XIV. Protecting Children from Environmental Health and Safety Risks
XV. Environmental Impacts
XVI. Public Participation--Notice of Hearing
XVII. Summary and Explanation of the Standards
XVIII. Authority and Signature
XIX. Proposed Standards

II. Issues

    OSHA requests comment on all relevant issues, including health 
effects, risk assessment, significance of risk determination, 
technological and economic feasibility, and the provisions of the 
proposed regulatory text. OSHA is especially interested in responses, 
supported by evidence and reasons, to the following questions:

Health Effects

    1. OSHA has described a variety of studies addressing the major 
adverse health effects that have been associated with exposure to 
Cr(VI). Has OSHA adequately identified and documented all critical 
health impairments associated with occupational exposure to Cr(VI)? Are 
there any additional studies or other data that would controvert the 
information discussed or significantly enhance the determination of 
material health impairment or the assessment of exposure-response 
relationships? Submit any relevant information, and explain your 
reasoning for recommending the inclusion of any studies you suggest.
    2. Using currently available epidemiologic and experimental 
studies, OSHA has made a preliminary determination that all Cr(VI) 
compounds (e.g., water soluble, insoluble and slightly soluble) possess 
carcinogenic potential and thus present a lung cancer risk to exposed 
workers. Is this determination correct? Are there additional data OSHA 
should consider in evaluating the carcinogenicity or relative 
carcinogenic potencies of different Cr(VI) compounds?

Risk Assessment

    3. In its preliminary assessment of risk, OSHA has relied primarily 
on two epidemiologic cohort studies of chromate production workers to 
estimate the lung cancer risk to workers exposed to Cr(VI) (Exs. 31-22-
11; 33-10). Are there any other studies that you believe are better 
suited to estimating the risk to exposed workers; if so, please provide 
the studies and explain why you believe they are better.
    4. OSHA is aware of two cohorts (i.e., Alexander cohort, Ex. 31-16-
3, and Pastides cohort, Ex. 35-279) in which a sizable number of 
workers were probably exposed to low Cr(VI) air levels (e.g., < 10 
[mu]g/m3) more consistent with concentrations found in the 
workplace today. However, OSHA believes the period of follow-up 
observation (median < 10 yr), the young age (< 45 yr at end of follow-up) 
and the low number of observed lung cancers (< =15 lung cancers) 
severely limits these cohorts as primary data sets for quantitative 
risk analysis. Other limitations to the Alexander study include a lack 
of data on workers who were employed between 1940 and 1974, but whose 
employment ended prior to 1974, and on exposures prior to 1974. Are 
there updated analyses available for the Alexander and Pastides 
cohorts? How many years do these cohorts need to be followed and how 
many lung cancers need to be observed in order for these data sets to 
provide insight into the shape of the exposure-response curve at lower 
levels of Cr(VI) exposure (e.g., 0.5 to 5 [mu]g/m3)? In the 
case of the Alexander cohort, is there additional information on cohort 
members' exposures prior to 1974 or workers who left prior to 1974 that 
could improve the analysis? Are there other cohorts available to look 
at low exposures?
    5. OSHA has relied upon a linear relative risk model and cumulative 
Cr(VI) exposure for estimating the lifetime occupational lung cancer 
risk among Cr(VI)-exposed workers. In particular, OSHA has made a 
preliminary determination that a threshold model is not appropriate for 
estimating the lung cancer risk associated with Cr(VI). However, there 
is some evidence that pathways (e.g., extracellular reduction, DNA 
repair, cell apoptosis, etc.) may exist within the lung that protect 
against Cr(VI)-induced respiratory carcinogenesis, and may potentially 
introduce non-linearities into the Cr(VI) exposure-cancer response. Is 
there convincing scientific evidence of a non-linear exposure-response 
relationship in the range of occupational exposures of interest to 
OSHA? If so, are there sufficient data to define a non-linear approach 
that would provide more reliable predictions of risk than the linear 
relative risk model used by OSHA?
    6. OSHA's estimates of lung cancer risk are based on workers 
primarily exposed to highly water-soluble sodium chromate and sodium 
dichromate. OSHA has preliminarily concluded that the risk for workers 
exposed to equivalent levels of other Cr(VI) compounds will be of a 
similar magnitude or, in the case of some Cr(VI) compounds, possibly 
greater than the risks projected in the OSHA quantitative risk 
assessment. Is this determination appropriate? Are there sufficient 
data to reliably quantify the risk from occupational exposure to 
specific Cr(VI) compounds? If so, explain how the risk could be 
estimated.
    7. The preliminary quantitative risk assessment relies on two (Gibb 
and Luippold) cohort studies in which most workers were exposed higher 
Cr(VI) levels than the PEL proposed by OSHA, for shorter durations than 
a working lifetime exposure. The risks estimated by OSHA for lifetime 
exposure to the proposed PEL, therefore, carry the assumption that a 
cumulative exposure achieved by short duration exposure to higher 
Cr(VI) air levels (e.g., exposed 3 years to 15 [mu]g/m3) 
leads to the same risk as an equivalent cumulative exposure achieved by 
longer duration exposure to

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lower Cr(VI) exposure (e.g, exposed 45 years to 1 [mu]g/m3). 
OSHA preliminarily finds this assumed exposure equivalency to represent 
an uncertainty in the estimates of risk but does not have information 
that indicates this uncertainty introduces serious error in its 
predictions of risk. Does the OSHA exposure-response assessment based 
on the higher Cr(VI) air levels and/or shorter durations experienced by 
the Gibb and Luippold cohorts lead to a serious underprediction or 
overprediction in estimated risks for the occupational exposure 
scenarios of interest to OSHA? Please provide any data to support your 
rationale.
    8. OSHA has made a preliminary determination that suitable data are 
not available for making quantitative risk estimates for the non-cancer 
adverse health effects associated with exposure to Cr(VI) (e.g., nasal 
septum ulcerations and perforations, asthma, irritant and allergic 
contact dermatitis). Are there suitable data for a quantitative 
estimation of risk for non-cancer adverse effects that OSHA should 
include in its final quantitative risk assessment? If so, what models 
or approaches should be used?
    9. Are there other factors OSHA should take into consideration in 
its final quantitative risk assessment to better characterize the risks 
associated with exposure to Cr(VI)?

Technologic and Economic Feasibility

    10. In its Preliminary Economic Analysis of the proposed standard, 
OSHA presents a profile of the affected worker population. In that 
profile are estimates of the number of affected workers by application 
group and job category and the distribution of exposures by job 
category. Are there additional data that will enable the Agency to 
refine its profile of the worker population exposed to Cr(VI)? If so, 
how should OSHA use these data in making such revisions?
    11. What are the job categories in which employees are potentially 
exposed to Cr(VI) in your company or industry? For each job category, 
provide a brief description of the operation and describe the job 
activities that may lead to Cr(VI) exposure. How many employees are 
exposed, or have the potential for exposure, to Cr(VI) in each job 
category in your company or industry? What are the frequency, duration 
and levels of exposures to Cr(VI) at each job category in your company 
or industry? Where commenters are able to provide exposure data, OSHA 
requests that, where possible, exposure data be personal samples with 
clear descriptions of the length of the sample and analytical method. 
Exposure data that provide information concerning the controls in place 
are more valuable than exposure data without such information.
    12. Have there been technological changes within your industry that 
have influenced the magnitude, frequency, or duration of exposure to 
Cr(VI) or the means by which employers attempt to control exposures? 
Describe in detail these technological changes and their effects on 
Cr(VI) exposures and methods of control.
    13. Has there been a trend within your industry to eliminate Cr(VI) 
from production processes, products and services? If so, comments are 
requested on the success of substitution efforts. Commenters should 
estimate the percentage reduction in Cr(VI), and the extent to which 
Cr(VI) is still necessary in their processes within product lines or 
production activities. OSHA also requests that commenters describe any 
technical, economic or other deterrents to substitution.
    14. Does any job category or employee in your workplace have 
exposures to Cr(VI) that raw air monitoring data do not adequately 
portray due to the short duration, intermittent or non-routine nature, 
or other unique characteristics of the exposure? Please explain your 
response and indicate peak levels, duration and frequency of exposures 
for employees in these job categories.
    15. OSHA requests the following information regarding engineering 
and work practice controls in your workplace or industry:
    a. Describe the operations in which the proposed PEL is being 
achieved most of the time by means of engineering and work practice 
controls.
    b. What engineering and work practice controls have been 
implemented in these operations?
    c. For all operations in facilities where Cr(VI) is used, what 
engineering and work practice controls have been implemented? If you 
have installed engineering controls or adopted work practices to reduce 
exposure to Cr(VI), describe the exposure reduction achieved and the 
cost of these controls. Where current work practices include the use of 
regulated areas and hygiene facilities, provide data on the 
implementation of these controls, including data on the costs of 
installation, operation, and maintenance associated with these 
controls.
    d. Describe additional engineering and work practice controls which 
could be implemented in each operation where exposure levels are 
currently above the proposed PEL to further reduce exposure levels.
    e. When these additional controls are implemented, to what levels 
can exposure be expected to be reduced, or what per cent reduction is 
expected to be achieved?
    f. What are the costs and amount of time needed to develop, install 
and implement these additional controls? Will the added controls affect 
productivity?
    g. Are there any processes or operations for which it is not 
reasonably possible to implement engineering and work practice controls 
within two years to achieve the proposed PEL? If so, would allowing 
additional time for employers to implement engineering and work 
practice controls make compliance possible? How much additional time 
would be necessary?
    16. OSHA requests information on whether there are any limited or 
unique conditions or job tasks in Cr(VI) manufacture or use where 
engineering and work practice controls are not available or are not 
capable of reducing exposure levels to or below the proposed PEL most 
of the time. Provide data and evidence to support your response.
    17. In its Preliminary Economic Analysis, OSHA presents estimated 
baseline levels of use of personal protective equipment (PPE) and the 
incremental costs associated with the proposed standard. Are OSHA's 
estimated compliance rates reasonable? Are OSHA's estimates of PPE 
costs, and the assumptions underlying these estimates, consistent with 
current industry practice? Comments are solicited on OSHA's analysis of 
PPE costs.
    18. In its Preliminary Economic Analysis, OSHA presents estimated 
baseline levels of communication of Cr(VI)-related hazards and the 
incremental costs associated with the additional requirements for 
communication in the proposed standard. OSHA requests information on 
hazard communication programs addressing Cr(VI) that are currently 
being implemented by employers and any necessary additions to those 
programs that are anticipated in response to the proposed standard. Are 
OSHA's baseline estimates and unit costs for training reasonable and 
consistent with current industry practice?

Effects on Small Entities

    19. Will difficulties be encountered by small entities when 
attempting to comply with requirements of the proposed standard? Can 
any of the

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proposal's requirements be deleted or simplified for small entities, 
while still protecting the health of employees? Would a longer time 
allowed for compliance for small entities make a difference to their 
ability to comply, and if so, why? (Information submitted in the SBREFA 
process is part of the record and need not be resubmitted).

Economic Impacts and Economic Feasibility

    20. OSHA, in its Preliminary Economic Analysis, has estimated, by 
application group, compliance costs per affected entity and the likely 
impacts on revenues and profits under alternative market scenarios. 
OSHA requests that affected employers provide comment on OSHA's 
estimate of revenue, profit, and the impacts of costs for their 
industry or application group. Are there special circumstances--such as 
unique cost factors, foreign competition, or pricing constraints--that 
OSHA needs to consider when evaluating economic impacts for particular 
application groups? Comments are requested on OSHA's analysis of 
economic feasibility in the PEA.

Overlapping and Duplicative Regulations

    21. Do any federal regulations duplicate, overlap, or conflict with 
the proposed Cr(VI) standard?
    22. In some facilities, adjustments in ventilation systems to 
comply with the proposed PEL may require additional time and expense to 
retest these systems to ensure compliance with EPA requirements or 
state requirements. OSHA requests information and comment indicating 
how frequently retesting would be required, and the time and costs 
involved in such retesting.

Environmental Impacts

    23. Submit any data, information, or comments pertaining to 
possible environmental impacts of adopting this proposal, such as the 
following:
    a. Any positive or negative environmental effects that could 
result;
    b. Any irreversible commitments of natural resources which could be 
involved; and
    c. Estimates of the effect of the proposed standard on the levels 
of Cr(VI) in the environment.
    In particular, consideration should be given to the potential 
direct or indirect impacts of the proposal on water and air pollution, 
energy use, solid waste disposal, or land use.
    d. Some small entity representatives noted that OSHA PELs are 
sometimes used to set ``fence line'' standards for air pollutants. OSHA 
is unable to find evidence of states formally using this procedure, 
though some states may use such a procedure informally. Do any states 
or other air pollution authorities base standards on OSHA PELs? What 
effects might this have on the environment and on environmental 
compliance?

Provisions of the Standard

    24. OSHA's safety and health advisory committees for Construction 
and Maritime advised the Agency to take into consideration the unique 
nature of their work environments by either settings separate standards 
or making accommodations for the differences in work environments in 
construction and maritime. To account for differences in the workplace 
environment for these different sectors OSHA has proposed separate 
standards for general industry, construction, and shipyards. Is this 
approach appropriate? What other approaches should the Agency consider? 
Please provide a rationale for your response.
    25. OSHA has not proposed to cover agriculture, because the Agency 
is not aware of significant exposures to Cr(VI) in agriculture. Is this 
determination correct?
    26. OSHA has proposed to regulate exposures to all Cr(VI) 
compounds. As discussed in the health effects section of this preamble, 
the Agency has made a preliminary determination that the existing data 
support coverage of all Cr(VI) compounds in the scope of the proposed 
standard. Is this an appropriate determination or are there additional 
data that support the exclusion of certain compounds from the scope of 
the final standard? If so, describe specifically how these data would 
support a decision to exclude certain compounds from the scope of the 
final rule.
    27. OSHA has made a preliminary determination to exclude Cr(VI) 
exposures due to work with portland cement from the scope of the 
construction standard. OSHA believes that guidance efforts by the 
Agency may be more suitable for addressing the dermal hazards 
associated with portland cement use in construction settings. OSHA's 
Advisory Committee for Construction Safety and Health (ACCSH) advised 
OSHA to include construction cement work under the proposed standard 
because of the known hazards associated with wet cement and the large 
number of workers exposed to wet cement in construction work settings. 
In particular ACCSH advised OSHA that only certain provisions might be 
necessary for workers exposed to wet cement (e.g., protective work 
clothing, hygiene areas and practices, medical surveillance for signs 
and symptoms of adverse health effects only, communication of hazards 
and recordkeeping for medical surveillance and training). Other 
provisions, ACCSH advised, might not be necessary (e.g., permissible 
exposure levels, exposure assessment, methods of compliance and 
respiratory protection). Should OSHA expand the scope of the 
construction proposal to include Cr(VI) exposures from portland cement? 
If so, what would be the best approach for addressing the dermal 
hazards from Cr(VI) faced by these workers? If Cr(VI) exposure from 
portland cement work in construction is included in the final standard, 
should only certain provisions such as those outlined by ACCSH be 
considered?
    28. OSHA has proposed to include exposure to Cr(VI) from portland 
cement in the scope of the standard for general industry. The Agency 
believes that the potential for airborne exposure to Cr(VI) in general 
industry due to work with portland cement, as indicated by the profile 
of exposed workers presented in Table IX-2 of this preamble, is higher 
than in the construction industry. OSHA acknowledges, however, that the 
exposure profile indicates that no workers are exposed to Cr(VI) at 
levels over the proposed action level. Given the low level of airborne 
exposure among cement workers in general industry, should OSHA exclude 
exposures to Cr(VI) from portland cement from the scope of the general 
industry standard? OSHA seeks data to help inform this issue, and 
solicits comments on particular provisions of the general industry and 
construction standards that may or may not be appropriate for cement 
workers.
    29. OSHA has proposed to exempt from coverage Cr(VI) exposures 
occurring in the application of pesticides in general industry (such as 
the treatment of wood with chromium copper arsenate (CCA)) because 
pesticide application is regulated by EPA, and section 4(b)(1) of the 
OSH Act precludes OSHA from regulating where other Federal agencies 
exercise their statutory authority to do so. OSHA has proposed to cover 
exposures resulting from use of treated materials. Is this approach 
appropriate? Are there any instances where EPA-regulated pesticide 
application occurs in construction or shipyard workplaces?
    30. Describe any additional industries, processes, or applications 
that should be exempted from the Cr(VI) standard and provide detailed 
reasons for any requested exemption. In

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particular, are the epidemiologic and experimental studies sufficient 
to support OSHA's the inclusion of various industries or processes 
under the scope of the proposed standard? Please provide the rationale 
and supporting data for your response.
    31. Can the proposed Cr(VI) standard for the construction industry 
be modified in any way to better account for the workplace conditions 
in that industry, while still providing appropriate protection to 
Cr(VI)-exposed workers in that industry? Would an alternative approach 
similar to that used in OSHA's asbestos standard, where the application 
of specified controls in certain situations would be considered 
adequate to meet the requirements of the standard, be useful? Is there 
enough information available to define such technology specifications?
    32. Can the proposed Cr(VI) standard for shipyards be modified in 
any way to better account for the workplace conditions in that 
industry, while still providing appropriate protection to Cr(VI)-
exposed workers in that industry?
    33. OSHA has proposed a TWA PEL for Cr(VI) of 1.0 [mu]g/
m3. The Agency has made a preliminary determination that 
this is the lowest level that is both technologically and economically 
feasible and is necessary to reduce significant risks of material 
health impairment from exposure to Cr(VI). Is this PEL appropriate and 
is it adequately supported by the existing data? If not, what PEL would 
be more appropriate or would more adequately protect employees from 
Cr(VI)-associated health risks? Provide evidence to support your 
response.
    34. Should different PELs be established for different Cr(VI) 
compounds? If so, how should they be established? Where possible, 
provide specific detail about how different PELs could be established 
and how the Agency should apply those PELs in instances where workers 
may be exposed to more than one Cr(VI) compound.
    35. OSHA has proposed an action level for Cr(VI) exposure in 
general industry, but not in construction or shipyards. Is this an 
appropriate approach? Should OSHA set an action level for exposure to 
Cr(VI) in construction and shipyards? Should the proposed action level 
in general industry be retained in the final rule?
    36. If an action level is included in the final rule, is the 
proposed action level for general industry (0.5 [mu]g/m3) 
the appropriate level for the PEL under consideration? If not, at what 
level should the action level be set?
    37. If an action level is included in the final rule, which 
provisions should be triggered by exposure above the action level? 
Indicate the basis for your position and include any supporting 
information.
    38. If no action level is included in the final rule, which 
provisions should apply to all Cr(VI)-exposed workers? Which provisions 
should be triggered by the PEL? Are there any other appropriate 
triggers for the requirements of the standard?
    39. Should OSHA set a short-term exposure limit (STEL) or ceiling 
for exposure to Cr(VI)? If so, please specify the appropriate air 
concentration and the rationale for its selection.
    40. Do you conduct initial air monitoring or do you rely on 
objective data to determine Cr(VI) exposures? Describe any other 
approaches you have implemented for assessing an employee's initial 
exposure to Cr(VI).
    41. Describe any follow-up or subsequent exposure assessments that 
you conduct. How often do you conduct such follow-up or subsequent 
exposure assessments? Please comment on OSHA's estimate of baseline 
industry practice and the projected costs for initial and periodic 
exposure assessment. Are OSHA's estimates consistent with current 
industry practice?
    42. Do shipyard employers presently measure their employees' 
exposure to Cr(VI)? If not, do they use some alternative method of 
identifying which employees may be over-exposed to Cr(VI)?
    43. OSHA has proposed specific requirements for exposure assessment 
in general industry, but has not proposed that these requirements apply 
to construction or shipyard employers. Should requirements for exposure 
assessment in construction or shipyards be included in the final Cr(VI) 
standard? Are there any advantages to requiring construction or 
shipyard employers to measure their employees' exposures to Cr(VI)? If 
so, would the exposure assessment requirements proposed for general 
industry be appropriate? Would construction or shipyard employers 
encounter situations where monitoring would be infeasible if they were 
required to follow the exposure assessment requirements proposed for 
employers in general industry? Indicate the basis for your position and 
include any supporting information. What types of exposure assessment 
strategies are effective for assessing worker exposures at construction 
and shipyard worksites?
    44. Should requirements for exposure assessment in general industry 
be included in the final Cr(VI) standard, or would the performance-
oriented requirement proposed for construction and shipyards be more 
appropriate? Indicate the basis for your position and include any 
supporting information.
    45. OSHA has proposed that exposure monitoring in general industry 
be conducted at least every six months if exposures are above the 
action level but below the PEL, and at least every three months if 
exposures are at or above the PEL. Are these proposed frequencies 
appropriate? If not, what frequency of monitoring would be more 
appropriate, and why?
    46. OSHA has proposed that regulated areas be established in 
general industry wherever an employee's exposure to airborne 
concentrations of Cr(VI) is, or can reasonably be expected to be, in 
excess of the PEL. OSHA seeks comments on this provision and in 
particular:
    a. Describe any work settings where establishing regulated areas 
could be problematic or infeasible. If establishing regulated areas is 
problematic, what approaches might be used to warn employees in such 
work settings of high risk areas (i.e., areas where the airborne 
concentrations of Cr(VI) exceed the PEL?).
    b. Should OSHA add hazards from eye or skin contact as a trigger 
for establishing regulated areas? Explain the basis for your position, 
and include any supporting information. c. Describe any methods 
currently used that have been found to be effective in establishing 
regulated areas.
    47. OSHA has not proposed requirements for establishment of 
regulated areas in construction or shipyards. Should requirements for 
regulated areas for construction or shipyards be included in the final 
Cr(VI) standard? If so, would the requirements for regulated areas 
proposed for general industry be appropriate? Are there any particular 
problems in construction or shipyard settings that make regulated areas 
problematic or infeasible? If requirements for regulated areas for 
construction or shipyards are not included in the final Cr(VI) 
standard, should OSHA include requirements for warning signs or other 
measures to alert employees of the presence of Cr(VI)? If so, what 
practical means could be used to determine where and when such labeling 
would be required? What potential difficulties might be encountered by 
using such an approach? Indicate the basis for your position and 
include any supporting information.
    48. Under the proposed standard, employers are required to use 
engineering and work practice controls

[[Page 59311]]

to reduce and maintain employee exposure to Cr(VI) to or below the PEL 
unless the employer can demonstrate that employees are not exposed 
above the PEL for 30 or more days per year, or the employer can 
demonstrate that such controls are not feasible. Is this approach 
appropriate for Cr(VI)? Indicate the basis for your position and 
include any supporting information.
    49. In OSHA's Cadmium standard (29 CFR 1010.1027), the Agency 
established separate engineering control air limits (SECALs) for 
certain processes in selected industries. SECALs were established where 
compliance with the PEL by means of engineering and work practice 
controls was infeasible. For these industries, a SECAL was established 
at the lowest feasible level that could be achieved by engineering and 
work practice controls. The PEL was set at a lower level, and could be 
achieved by any allowable combination of controls. SECALs thus allowed 
OSHA to establish a lower PEL for cadmium than would otherwise have 
been possible, given technological feasibility constraints. Should OSHA 
establish SECALs for Cr(VI) in any industries or processes? If so, in 
what industries or processes, and at what levels? Provide rationale to 
support your position.
    50. The proposed standard prohibits the use of job rotation for the 
sole purpose of lowering employee exposures to Cr(VI). Are there any 
circumstances where this practice should be allowed in order to meet 
the proposed PEL?
    51. OSHA is proposing that employers provide appropriate protective 
clothing and equipment when a hazard is present or is likely to be 
present from skin or eye contact with Cr(VI). OSHA would expect an 
employer to exercise common sense and appropriate expertise to 
determine if a hazard is present or likely to be present. Is this 
approach appropriate? Are there other approaches that would be better 
for characterizing eye and skin contact with Cr(VI)? For example, are 
there methods to measure dermal exposure that could be used to 
routinely monitor worker exposure to Cr(VI) that OSHA should consider 
including in the final standard?
    52. For employers whose employees are exposed to Cr(VI), what 
approaches do you currently use to assess potential hazards from eye or 
skin contact with Cr(VI)? What protective clothing and equipment do you 
use to protect employees from eye or skin contact with Cr(VI)? What 
does this protective clothing and equipment cost? Who pays for the 
protective clothing and equipment?
    53. Should OSHA require the use of protective clothing and 
equipment for those employees who are exposed to airborne 
concentrations of Cr(VI) in excess of the PEL? If so, what type of 
protective clothing and equipment might be necessary?
    54. OSHA has proposed to require that employers pay for protective 
clothing and equipment provided to employees. The Agency seeks comment 
on this provision, in particular:
    a. Should OSHA refrain from requiring employer payment, and follow 
the outcome of the rulemaking addressing employer payment for personal 
protective equipment (64 FR 15401 (3/31/99))?
    b. Are there circumstances where employers should not be required 
to pay for clothing and equipment used to protect employees from Cr(VI) 
hazards, such as situations where it is customary for employees to 
provide their own protective clothing and equipment (i.e., ``tools of 
the trade'')?
    c. OSHA realizes that there is frequent turnover in the 
construction industry, where employees frequently move from jobsite to 
jobsite. This is an important factor because an employer with a high-
turnover workplace would have to buy protective clothing and equipment 
for more employees if the protective clothing and equipment could only 
be used by one employee. The Agency requests comment on whether this 
proposal's requirement for employer payment for protective clothing and 
equipment is appropriate in the construction industry. Are there any 
alternative approaches that would be responsive to the turnover 
situation and would also be protective of construction workers? Are 
there any other issues specific to the construction industry that OSHA 
should be consider in this rulemaking?
    d. At some ports, employees are hired for jobs in shipyards, 
longshoring, and marine terminals through a labor pool, and a single 
employee may work for five different employers in the same week. How do 
these factors affect who is required to pay for protective clothing and 
equipment? Are there any other issues specific to shipyards, 
longshoring, or marine terminals that OSHA should consider in this 
rulemaking?
    55. OSHA is proposing that washing facilities capable of removing 
Cr(VI) from the skin be provided to affected employees, but does not 
propose that showers be required. Should OSHA include requirements to 
provide showers to employees exposed to Cr(VI)? If so, under what 
circumstances should showers be required? Describe work situations 
where showers are either unnecessary for employee protection or that 
present obstacles to their implementation and describe any such 
obstacles.
    56. OSHA has not included housekeeping provisions in the proposed 
Cr(VI) standard for construction or shipyards. The Agency has made a 
preliminary determination that the housekeeping requirements proposed 
for general industry are likely to be difficult to implement in the 
construction and shipyard environments. Is this an appropriate 
determination? If not, what practicable housekeeping measures can 
construction and shipyard employers take to reduce employee exposure to 
Cr(VI) at the work site? What housekeeping activities are currently 
being performed?
    57. Is medical surveillance being provided to Cr(VI)-exposed 
employees at your worksite? If so,
    a. What exposure levels or other factors trigger medical 
surveillance?
    b. What tests or evaluations are included in the medical 
surveillance program?
    c. What benefits have been achieved from the medical surveillance 
program?
    d. What are the costs of the medical surveillance program? How do 
your current costs compare with OSHA's estimated unit costs for the 
physical examination and employee time involved in the medical 
surveillance program? Please comment on OSHA's baseline assumptions and 
cost estimates for medical surveillance.
    e. How many employees are included in your medical surveillance 
program?
    f. In what North American Industry Classification System (NAICS) 
code does your workplace fall?
    58. OSHA has proposed that medical surveillance be triggered in 
general industry in the following circumstances: (1) When exposure to 
Cr(VI) is above the PEL for 30 days or more per year; (2) after an 
employee experiences signs or symptoms of the adverse health effects 
associated with Cr(VI) exposure (e.g., dermatitis, asthma); or (3) 
after exposure in an emergency. OSHA seeks comments as to whether or 
not these are appropriate triggers for offering medical surveillance 
and whether there are additional triggers that should be included. 
Should OSHA require that medical surveillance be triggered in general 
industry only upon an employee experiencing signs and symptoms of 
disease or after exposure in an emergency, as in the construction and 
maritime standards? OSHA also solicits comment on the optimal frequency 
of medical surveillance.

[[Page 59312]]

    59. OSHA has proposed that medical surveillance be triggered in 
construction and shipyards in the following circumstances: (1) after an 
employee experiences signs or symptoms of the adverse health effects 
associated with Cr(VI) exposure (e.g., dermatitis, asthma); or (2) 
after exposure in an emergency. Should medical surveillance in 
construction or shipyards be triggered by exposure to Cr(VI) above the 
PEL for 30 days or more per year, as proposed for general industry? 
OSHA seeks comments as to whether or not the proposed triggers are 
appropriate for offering medical surveillance and whether there are 
additional triggers that should be included.
    60. OSHA has not included certain biological tests (e.g., blood or 
urine monitoring, skin patch testing for sensitization, expiratory flow 
measurements for airway restriction) as a part of the medical 
evaluations required to be provided to employees offered medical 
surveillance under the proposed standard. OSHA has preliminarily 
determined that the general application of these tests is of uncertain 
value as an early indicator of potential Cr(VI)-related health effects. 
However, the proposed standard does allow for the provision of any 
tests (which could include urine or blood tests) that are deemed 
necessary by the physician or other licensed health care professional. 
Are there any tests (e.g., urine tests, blood tests, skin patch tests, 
airway flow measurements, or others) that should be included under the 
proposed standard's medical surveillance provisions? If there are any 
that should be included, explain the rationale for their inclusion, 
including the benefit to worker health they might provide, their 
utility and ease of use in an occupational health surveillance program, 
and associated costs.
    61. OSHA has not included requirements for medical removal 
protection (MRP) in the proposed standard. OSHA has made a preliminary 
determination that there are few instances where temporary worker 
removal and MRP will be useful. The Agency seeks comment as to whether 
the final Cr(VI) standard should include provisions for the temporary 
removal and extension of MRP benefits to employees with certain Cr(VI)-
related health conditions. In particular, what endpoints should be 
considered for temporary removal and for what maximum amount of time 
should MRP benefits be extended? OSHA also seeks information on whether 
or not MRP is currently being used by employers with Cr(VI)-exposed 
workers, and the costs of such programs.
    62. OSHA has proposed that employers provide hazard information to 
employees in accordance with the Agency's Hazard Communication standard 
(29 CFR 1910.1200), and has also proposed additional requirements 
regarding signs, labels, and additional training specific to work with 
Cr(VI). Should OSHA include these additional requirements in the final 
rule, or are the requirements of the Hazard Communication standard 
sufficient?
    63. OSHA has proposed that bags or containers of laundry 
contaminated with Cr(VI) bear warning labels. Will this cause you to 
alter your current laundry practices? Are there laundries in your area 
that would accept such laundry? Would laundering costs increase? If so, 
by how much?
    64. OSHA requests comment on the time allowed for compliance with 
the provisions of the proposed standard. Is the time proposed 
sufficient, or is a longer or shorter phase-in of requirements 
appropriate? Identify any industries, processes, or operations that 
have special needs for additional time, the additional time required 
and the reasons for the request.
    65. Some other OSHA health standards have included appendices that 
address topics such as the hazards associated with the regulated 
substance, health screening considerations, occupational disease 
questionnaires, and PLHCP obligations. OSHA has not proposed to include 
any appendices with the Cr(VI) rule because the Agency has made a 
preliminary determination that such topics would be best addressed with 
guidance materials. What would be the advantage of including such 
appendices in the final rule? If you believe they should be included, 
what information should be included? What would be the disadvantage of 
including these appendices in the final rule?

III. Pertinent Legal Authority

    The purpose of the Occupational Safety and Health Act, 29 U.S.C. 
651 et seq. (``the Act'') is to ``assure so far as possible every 
working man and woman in the nation safe and healthful working 
conditions and to preserve our human resources.'' 29 U.S.C. 651(b). To 
achieve this goal Congress authorized the Secretary of Labor to 
promulgate and enforce occupational safety and health standards. 29 
U.S.C. 655(a)(authorizing summary adoption of existing consensus and 
federal standards within two years of Act's enactment), 
655(b)(authorizing promulgation of standards pursuant to notice and 
comment), 654(b)(requiring employers to comply with OSHA standards).
    A safety or health standard is a standard ``which requires 
conditions or the adoption of or use of one or more practices, means, 
methods, operations or processes, reasonably necessary or appropriate 
to provide safe or healthful employment or places of employment 29 
U.S.C. 652(8).
    A standard is reasonably necessary or appropriate within the 
meaning of Section 652(8) if it substantially reduces or eliminates 
significant risk, and is economically feasible, technologically 
feasible, cost effective, consistent with prior Agency action or 
supported by a reasoned justification for departing from prior Agency 
actions, supported by substantial evidence, and is better able to 
effectuate the Act's purpose than any national consensus standard it 
supersedes. See 58 Fed. Reg. 16612-16616 (March 30, 1993).
    OSHA has generally considered, at minimum, fatality risk of 1/1000 
over a 45-year working lifetime to be a significant health risk. See 
the Benzene standard, Industrial Union Dep't v. American Petroleum 
Institute, 448 U.S. 607, 646 ((1980); the Asbestos standard, 
International Union, UAW v. Pendergrass, 878 F.2d 389, 393 (D.C. Cir. 
1989).
    A standard is technologically feasible if the protective measures 
it requires already exist, can be brought into existence with available 
technology, or can be created with technology that can reasonably be 
expected to be developed. American Textile Mfrs. Institute v. OSHA, 452 
U.S. 490, 513 (1981)(``ATMI'') American Iron and Steel Institute v. 
OSHA, 939 F.2d 975, 980 (D.C. Cir. 1991)(``AISI'').
    A standard is economically feasible if industry can absorb or pass 
on the costs of compliance without threatening its long-term 
profitability or competitive structure. See ATMI, 452 U.S. at 530 n. 
55; AISI, 939 F. 2d at 980.
    A standard is cost effective if the protective measures it requires 
are the least costly of the available alternatives that achieve the 
same level of protection. ATMI, 453, U.S, at 514 n. 32; International 
Union, UAW v. OSHA, 37 F.3d 665, 668 (D.C., Cir 1994)(``LOTO III'').
    All standards must be highly protective. See 58 FR 16614-16615; 
LOTO III, 37 F. 3d at 669. However, health standards must also meet the 
``feasibility mandate'' of Section 6(b)(7) of the Act, 29 U.S.C. 
655(b)(5). Section 6(b)(5) requires OSHA to select ``The most 
protective standard consistent with feasibility'' that is needed to 
reduce significant risk when regulating health standards. ATMI, 452 
U.S. at 509.

[[Page 59313]]

    Section 6(b)(5) also directs OSHA to base health standard on ``the 
best available evidence,'' including research, demonstrations, and 
experiments. 29 U.S.C. 655(b)(5). OSHA shall consider ``in addition to 
the attainment of the highest degree of health and safety protection * 
* * feasibility and experience gained under this and other health and 
safety laws.'' Id.
    Section 6(b)(7) authorizes OSHA to include among a standard's 
requirements labeling, monitoring, medical testing and other 
information gathering and transmittal provisions. 29 U.S.C. 655(b)(7).
    Finally, whenever practical, standards shall ``be expressed in 
terms of objective criteria and of the performance desired.'' Id.

IV. Events Leading to the Proposed Standards

    OSHA's present standards for workplace exposure to Cr(VI) were 
adopted in 1971, pursuant to section 6(a) of the OSH Act, from a 1943 
American National Standards Institute (ANSI) recommendation originally 
established to control irritation and damage to nasal tissues (Ex. 20-
3). OSHA's general industry standard set a permissible exposure limit 
(PEL) of 1 mg chromium trioxide per 10 m3 air in the 
workplace (1 mg/10 m3 CrO3) as a ceiling 
concentration, which corresponds to a concentration of 52 [mu]g/
m3 Cr(VI). A separate rule promulgated for the construction 
industry set an eight-hour time-weighted-average PEL of 1 mg/10 
m3 CrO3, also equivalent to 52 [mu]g/
m3 Cr(VI), adopted from the American Conference of 
Governmental Industrial Hygienists (ACGIH) 1970 Threshold Limit Value 
(TLV) (36 FR 7340 (4/17/71)).
    Following the ANSI standard of 1943, other occupational and public 
health organizations evaluated Cr(VI) as a workplace and environmental 
hazard and formulated recommendations to control exposure. The ACGIH 
first recommended control of workplace exposures to chromium in 1946, 
recommending a time-weighted average Maximum Allowable Concentration 
(later called a Threshold Limit Value) of 100 [mu]g/m3 for 
chromic acid and chromates as Cr2O3 (Ex. 5-37), 
and classified certain Cr(VI) compounds as class A1 (confirmed human) 
carcinogens in 1974. In 1975, the NIOSH Criteria for a Recommended 
Standard recommended that occupational exposure to Cr(VI) compounds 
should be limited to a 10-hour TWA of 1 [mu]g/m3, except for 
some forms of Cr(VI) then believed to be noncarcinogenic (Ex. 3-92). 
The National Toxicology Program's First Annual Report on Carcinogens 
identified calcium chromate, chromium chromate, strontium chromate, and 
zinc chromate as carcinogens in 1980 (Ex. 35-157).
    During the 1980s, regulatory and standards organizations came to 
recognize Cr(VI) compounds in general as carcinogens. The Environmental 
Protection Agency (EPA) Health Assessment Document of 1984 stated that 
``using the IARC [International Agency for Research on Cancer] 
classification scheme, the level of evidence available for the combined 
animal and human data would place hexavalent chromium Cr(VI) compounds 
into Group 1, meaning that there is decisive evidence for the 
carcinogenicity of those compounds in humans'' (Ex. 19-1, p. 7-107). In 
1988 IARC evaluated the available evidence regarding Cr(VI) 
carcinogenicity, concluding in 1990 that ``There is sufficient evidence 
in humans for the carcinogenicity of chromium[VI] compounds as 
encountered in the chromate production, chromate pigment production and 
chromium plating industries'', and ``sufficient evidence in 
experimental animals for the carcinogenicity of calcium chromate, zinc 
chromates, strontium chromate and lead chromates'(Ex. 18-3, p. 213). In 
September 1988, NIOSH advised OSHA to consider all Cr(VI) compounds as 
potential occupational carcinogens (Ex. 31-22-22, p. 8). ACGIH now 
classifies water-insoluble and water-soluble Cr(IV) compounds as class 
A1 carcinogens (Ex. 35-207). Current ACGIH standards include specific 
8-hour time-weighted average TLVs for calcium chromate (1 [mu]g/
m3), lead chromate (12 [mu]g/m3), strontium 
chromate (0.5 [mu]g/m3), and zinc chromates (10 [mu]g/
m3), and generic TLVs for water soluble (50 [mu]g/
m3) and insoluble (10 [mu]g/m3) forms of 
hexavalent chromium not otherwise classified, all measured as chromium 
(Ex. 35-207).
    In July 1993, OSHA was petitioned for an emergency temporary 
standard to reduce occupational exposures to Cr(VI) compounds (Ex. 1). 
The Oil, Chemical, and Atomic Workers International Union (OCAW) and 
Public Citizen's Health Research Group (HRG), citing evidence that 
occupational exposure to Cr(VI) increases workers' risk of lung cancer, 
petitioned OSHA to promulgate an emergency temporary standard to lower 
the PEL for Cr(VI) compounds to 0.5 [mu]g/m3 as an eight-
hour, time-weighted average (TWA). Upon review of the petition, OSHA 
agreed that there was evidence of increased cancer risk from exposure 
to Cr(VI) at the existing PEL, but found that the available data did 
not show the ``grave danger'' required to support an emergency 
temporary standard (Ex. 1-C). The Agency therefore denied the request 
for an emergency temporary standard, but initiated section 6(b)(5) 
rulemaking and began performing preliminary analyses relevant to the 
rule. In 1997, OSHA was sued by HRG for unreasonable delay in issuing a 
Cr(VI) standard. The U.S. Court of Appeals for the Third Court ruled in 
OSHA's favor and the Agency continued its data collection and analytic 
efforts on Cr(VI) (Ex. 35-208, p. 3). OSHA was sued again in 2002 by 
HRG for continued unreasonable delay in issuing a Cr(VI) standard (Ex. 
31-24-1). In August 2002, OSHA published a Request for Information on 
Cr(VI) to solicit additional information on key issues related to 
controlling exposures to Cr(VI)(67 FR 54389 (8/22/02)), and on December 
4, 2002 announced its intent to proceed with developing a proposed 
standard (Ex. 307). The Court ruled in favor of HRG on December 24, 
2002, ordering the Agency to proceed expeditiously with a Cr(VI) 
standard (Ex. 35-208). On April 2, 2003 the Court set deadlines of 
October 4, 2004 for publication of a proposed standard and January 18, 
2006 for publication of a final standard (Ex. 35-306).
    OSHA initiated Small Business Regulatory Enforcement Act (SBREFA) 
proceedings in 2003, seeking the advice of small business 
representatives on the proposed rule. The SBREFA panel, including 
representatives from OSHA, the Small Business Administration (SBA), and 
the Office of Management and Budget (OMB), was convened on December 23, 
2003. The panel conferred with representatives from small entities in 
chemical, alloy, and pigment manufacturing, electroplating, welding, 
aerospace, concrete, shipbuilding, masonry, and construction on March 
16-17, 2004, and delivered its final report to OSHA on April 20, 2004. 
The Panel's report, including comments from the small entity 
representatives (SERS) and recommendations to OSHA for the proposed 
rule, is available in the Cr(VI) rulemaking docket (Ex. 34).
    OSHA provided the Advisory Committee on Construction Safety and 
Health (ACCSH) and the Maritime Advisory Committee on Occupational 
Safety and Health (MACOSH) with copies of the draft proposed rule for 
review in early 2004. OSHA representatives met with ACCSH in February 
2004 and May 2004 to discuss the rulemaking and receive their comments 
and recommendations. On February 13, ACCSH recommended that portland 
cement should be included

[[Page 59314]]

within the scope of the proposed standard (Ex. 35-308, pp. 288-293) and 
that identical PELs should be set for the construction, maritime, and 
general industries (Ex. 35-308, pp. 293-297). The Committee recommended 
on May 18 that the construction industry should be included in the 
current rulemaking, and affirmed its earlier recommendation regarding 
portland cement. OSHA representatives met with MACOSH in March 2004. On 
March 3, MACOSH decided to collect and forward additional exposure 
monitoring data to OSHA to help the Agency better evaluate exposures to 
Cr(VI) in shipyards (Ex. 310, p. 208). MACOSH also recommended a 
separate Cr(VI) standard for the maritime industry, arguing that 
maritime involves different exposures and requires different means of 
exposure control than general industry and construction (Ex. 310, p. 
227).

V. Chemical Properties and Industrial Uses

    Chromium is a metal that exists in several oxidation or valence 
states, ranging from chromium (-II) to chromium (+VI). The elemental 
valence state, chromium (0), does not occur in nature. Chromium 
compounds are very stable in the trivalent state and occur naturally in 
this state in ores such as ferrochromite, or chromite ore 
(FeCr2O4). The hexavalent, Cr(VI) or chromate, is 
the second most stable state. It rarely occurs naturally; most Cr(VI) 
compounds are man made.
    Chromium compounds in higher valence states are able to undergo 
``reduction'' to lower valence states; chromium compounds in lower 
valence states are able to undergo ``oxidation'' to higher valence 
states. Thus, Cr(VI) compounds can be reduced to Cr(III) in the 
presence of oxidizable organic matter. Chromium can also be reduced in 
the presence of inorganic chemicals such as iron.
    Chromium does exist in less stable oxidation (valence) states such 
as Cr(II), Cr(IV), and Cr(V). Anhydrous Cr(II) salts are relatively 
stable, but the divalent state (II, or chromous) is generally 
relatively unstable and is readily oxidized to the trivalent (III or 
chromic) state. Compounds in valence states such as (IV) and (V) 
usually require special handling procedures as a result of their 
instability. Cr(IV) oxide (CrO2) is used in magnetic 
recording and storage devices, but very few other Cr(IV) compounds have 
industrial use. Evidence exists that both Cr(IV) and Cr(V) are formed 
as transient intermediates in the reduction of Cr(VI) to Cr(III) in the 
body.
    Chromium (III) is also an essential nutrient that plays a role in 
glucose, fat, and protein metabolism by causing the action of insulin 
to be more effective. Chromium picolinate, a trivalent form of chromium 
combined with picolinic acid, is used as a dietary supplement, because 
it is claimed to speed metabolism.
    Elemental chromium and the chromium compounds in their different 
valence states have various physical and chemical properties, including 
differing solubilities. Most chromium species are solid. Elemental 
chromium is a steel gray solid, with high melting and boiling points 
(1857 [deg]C and 2672 [deg]C, respectively), and is insoluble in water 
and common organic solvents. Chromium (III) chloride is a violet or 
purple solid, with high melting and sublimation points (1150 [deg]C and 
1300 [deg]C, respectively), and is slightly soluble in hot water and 
insoluble in common organic solvents. Ferrochromite is a brown-black 
solid; chromium (III) oxide is a green solid; and chromium (III) 
sulfate is a violet or red solid, insoluble in water and slightly 
soluble in ethanol. Chromium (III) picolinate is a ruby red crystal 
soluble in water (1 part per million at 25 [deg]C). Chromium (IV) oxide 
is a brown-black solid that decomposes at 300 [deg]C and is insoluble 
in water.
    Cr(VI) compounds have mostly lemon yellow to orange to dark red 
hues. They are typically crystalline, granular, or powdery although one 
compound (chromyl chloride) exists in liquid form. They range from very 
soluble to insoluble in water. For example, chromyl chloride is a dark 
red liquid that decomposes into chromate ion and hydrochloric acid in 
water. Chromic acids are dark red crystals that are very soluble in 
water. Other examples of soluble chromates are potassium chromate 
(lemon yellow crystals), sodium chromate (yellow crystals), and sodium 
dichromate (reddish to bright orange crystals). Nickel chromate, lead 
chromate oxide, and zinc chromate are completely insoluble in water. 
The nickel chromate (black crystals) dissolves in nitric acid and 
hydrogen peroxide. Lead chromate oxide is a red crystalline powder. The 
zinc chromate (lemon yellow crystals) decomposes in hot water and is 
soluble in acids and liquid ammonia. Examples of slightly soluble 
Cr(VI) compounds are barium (light yellow), calcium (yellow), lead 
(yellow to orange-yellow), and strontium (yellow) chromates, and zinc 
chromate hydroxide (yellow). They all exist in solid form as crystals 
or powder. Potassium zinc chromate hydroxide (greenish-yellow crystals) 
is also slightly soluble in water.
    Some major users of chromium are the metallurgical, refractory, and 
chemical industries. Chromium is used by the metallurgical industry to 
produce stainless steel, alloy steel, and nonferrous alloys. Chromium 
is alloyed with other metals and plated on metal and plastic substrates 
to improve corrosion resistance and provide protective coatings for 
automotive and equipment accessories. Welders use stainless steel 
welding rods when joining metal parts.
    Cr(VI) compounds are widely used in the chemical industry in 
pigments, metal plating, and chemical synthesis as ingredients and 
catalysts. Chromates are used as high quality pigments for textile 
dyes, paints, inks, glass, and plastics. Cr(VI) can be produced during 
welding operations even if the chromium was originally present in 
another valence state. While Cr(VI) is not intentionally added to 
portland cement, it is often present as an impurity.
    Occupational exposures to Cr(VI) can occur from inhalation of mists 
(e.g., chrome plating, painting), dusts (e.g., inorganic pigments), or 
fumes (e.g., stainless steel welding), and from dermal contact (cement 
workers).
    There are about thirty major industries and processes where Cr(VI) 
is used. These include producers of chromates and related chemicals 
from chromite ore, electroplating, welding, painting, chromate pigment 
production and use, steel mills, and iron and steel foundries. A 
detailed discussion of the uses of Cr(VI) in industry is found in 
Section IX of this preamble.

VI. Health Effects

    The studies of adverse health effects resulting from exposure to 
hexavalent chromium (Cr(VI)) in humans and experimental animals are 
summarized in the section below. Section VI includes information on the 
fate of Cr(VI) in the body and laboratory research that relates to its 
toxic mode of action. The primary health impairments from workplace 
exposure to Cr(VI) are lung cancer, asthma, and damage to the nasal 
epithelia and skin. This chapter on health effects will not attempt to 
describe every study ever conducted on Cr(VI) toxicity. Instead, only 
the most important articles and reviews of studies will be evaluated.

A. Absorption, Distribution, Metabolic Reduction and Elimination

    Chromium can exist in a number of valence states from -2 to +6 
valence. The most common forms are the elemental metal Cr(0), trivalent 
Cr(III), and hexavalent Cr(VI). Chromium exists naturally in the 
environment in

[[Page 59315]]

chromite ore as Cr(III). Cr(0) and Cr(VI), as well as Cr(III) are 
produced during industrial processes. Cr(VI) is the form considered to 
be the greatest health risk. A small amount of Cr(III) is needed for 
optimal insulin receptor function in human tissues but much larger 
amounts may be harmful. Much less is known about the toxicity of Cr(0), 
but it is believed to be converted to Cr(III) in the body and is not 
considered to be a serious health risk. Cr(VI) enters the body by 
inhalation, ingestion, or absorption through the skin. For occupational 
exposure, the airways and skin are the primary routes of uptake.
1. Deposition and Clearance of Inhaled Cr(VI) From the Respiratory 
Tract
    Various anatomical, physical and physiological factors determine 
both the fractional and regional deposition of inhaled particulate 
matter. Due to the airflow patterns in the lung more particles tend to 
deposit at certain preferred regions in the lung. Schlesinger and 
Lippman have shown a high degree of correlation between sites of 
greatest particle deposition in the tracheobronchial airways and 
increased incidence of bronchial tumors (Ex. 35-102). It is possible to 
have a buildup of chromium at certain sites in the bronchial tree that 
could create areas of very high chromium concentration. This would 
especially be true for occupational environments that are particularly 
dusty or contain other irritating aerosols.
    Large inhaled particles (>5 [mu]m) are efficiently removed from the 
air-stream in the extrathoracic region (Ex. 35-175). Particles greater 
than 2.5 [mu]m are generally deposited in the tracheobronchial regions, 
whereas particles less than 2.5 [mu]m are generally deposited in the 
pulmonary region. Some larger particles (>2.5 [mu]m) can reach the 
pulmonary region. The mucociliary escalator predominantly clears 
particles that deposit in the extrathoracic and the tracheobronchial 
region of the lung. Individuals exposed to high particulate levels of 
Cr(VI) may also have altered respiratory mucociliary clearance. 
Particulates that reach the alveoli can be absorbed into the 
bloodstream cleared by phagocytosis.
2. Absorption of Inhaled Cr(VI) Into the Bloodstream
    The absorption of inhaled chromium compounds depends on a number of 
factors, including physical and chemical properties of the particles 
(oxidation state, size, solubility) and the activity of alveolar 
macrophages (Ex. 35-41). The hexavalent chromate anion 
(CrO4)2-enter cells via facilitated diffusion 
through non-specific anion channels (similar to phosphate and sulfate 
anions). Suzuki et al. have demonstrated that Cr(VI) is rapidly and 
extensively transported to the bloodstream in rats (Ex. 35-97). They 
exposed rats to 7.3-15.9 mg Cr(VI)/m3 as potassium 
dichromate for 2-6 hours. Following exposure to Cr(VI), the ratio of 
blood chromium/lung chromium was 1.440.30 at 0.5 hours, 
0.810.10 at 18 hours, 0.850.20 at 48 hours, and 
0.960.22 at 168 hours after exposure.
    Once the Cr(VI) particles reach the alveoli, absorption into the 
bloodstream is greatly dependent on solubility. Bragt and van Dura 
demonstrated that more soluble chromates are absorbed faster than less 
soluble chromates (Ex. 35-56). Insoluble chromates are poorly absorbed 
and therefore have longer resident time in the lungs. They studied the 
kinetics of three Cr(VI) compounds: Sodium chromate, zinc chromate and 
lead chromate. They instilled 51chromium-labeled compounds 
(0.38 mg Cr(VI)/kg as sodium chromate, 0.36 mg Cr(VI)/kg as zinc 
chromate, or 0.21 mg Cr(VI)/kg as lead chromate) intratracheally in 
rats. Peak blood levels of 51chromium were reached after 30 
minutes for sodium chromate (0.35 [mu]g chromium/ml), and after 24 
hours for zinc chromate (0.60 [mu]g chromium/ml) and lead chromate 
(0.007 [mu]g chromium/ml). At 30 minutes after administration, the 
lungs contained 36, 25, and 81% of the respective dose of the sodium, 
zinc, and lead chromate. On day six, >80% of the dose of all three 
compounds had been cleared from the lungs, during which time the 
disappearance from lungs followed linear first-order kinetics. The 
residual amount left in the lungs on day 50 or 51 was 3.0, 3.9, and 
13.9%, respectively. From these results authors concluded that zinc 
chromate, which is less soluble than sodium chromate, is more slowly 
absorbed from the lungs. Lead chromate was more poorly and slowly 
absorbed, as indicated by very low levels in blood and greater 
retention in the lungs. The authors also noted that the kinetics of 
sodium and zinc chromates were very similar. Zinc chromate, which is 
less soluble than sodium chromate, was slowly absorbed from the lung, 
but the maximal blood levels were higher than those resulting from an 
equivalent dose of sodium chromate. The authors believe that this was 
probably due to irritative properties of the zinc chromate used, as it 
caused hemorrhages in the lungs which were macroscopically visible as 
early as 24 hours after intratracheal administration.
    The studies by Langard et al. and Adachi et al. provide further 
evidence of absorption of chromates from the lungs (Exs. 35-93; 189). 
Rats exposed to 2.1 mg Cr(VI)/m3 as zinc chromate for 6 
hours/day achieved steady state concentrations in the blood after 4 
days of exposure (Ex. 35-93). Adachi et al. studied rats that were 
subject to a single inhalation exposure to chromic acid mist generated 
from electroplating at a concentration of 3.18 mg Cr(VI)/m3 
for 30 minutes which was then rapidly absorbed from the lungs (Ex. 
189). The amount of chromium in the lungs of these rats declined from 
13.0 mg immediately after exposure to 1.1 mg after 4 weeks, with an 
overall half-life of five days.
    Several other studies have reported absorption of chromium from the 
lungs after intratracheal instillation (Exs. 7-9; 9-81; Visek et al. 
1953 as cited in Ex. 35-41). These studies indicated that 53-85% of 
Cr(VI) compounds (particle size < 5 [mu]m) were cleared from the lungs 
by absorption into the bloodstream or by mucociliary clearance in the 
pharynx; the rest remained in the lungs. Absorption of Cr(VI) from the 
respiratory tract of workers has been shown in several studies that 
identified chromium in the urine, serum and red blood cells following 
occupational exposure (Exs. 5-12; 35-294; 35-84).
    Evidence indicates that even chromates that are encapsulated in a 
paint matrix may be released in the lungs (Ex. 31-15, p. 2). LaPuma et 
al. measured the mass of Cr(VI) released from particles into water 
originating from three types of paint particles: solvent-borne expoxy 
(25% strontium chromate (SrCrO4)), water-borne expoxy (30% 
SrCrO4) and polyurethane (20% SrCrO4) (Ex. 31-2-
1). The mean fraction of Cr(VI) released into the water after one and 
24 hours for each primer averaged: 70% and 85% (solvent epoxy), 74% and 
84% (water epoxy), and 94% and 95% (polyurethane). Correlations between 
particle size and the fraction of Cr(VI) released indicated that 
smaller particles (< 5 m) release a larger fraction of Cr(VI) versus 
larger particles (>5 [mu]m). This study demonstrates that the paint 
matrix only modestly hinders Cr(VI) release into a fluid, especially 
with smaller particles. Larger particles, which contain the majority of 
Cr(VI) due to their size, appear to release proportionally less Cr(VI) 
(as a percent of total Cr(VI)) than smaller particles.
    A number of questions remain unanswered regarding encapsulated 
Cr(VI) and bioavailability from the lung. There is a lack of detailed 
information on the encapsulation process. The efficiency of 
encapsulation and whether all of the chromate molecules are

[[Page 59316]]

encapsulated is not known. The stability of the encapsulated product in 
physiological and environmental conditions has not been demonstrated. 
It would be useful to know if any processes can break the encapsulation 
during its use. Finally, the fate of inhaled encapsulated and 
unencapsulated Cr(VI) in the respiratory tract as well as the systemic 
tissues needs to be more thoroughly studied.
3. Dermal Absorption of Cr(VI)
    Both human and animal studies demonstrate that Cr(VI) compounds are 
absorbed after dermal exposure. Dermal absorption depends on the 
oxidation state of chromium, the vehicle and the integrity of the skin. 
Cr(VI) readily traverses the epidermis to the dermis (Exs. 9-49; 309). 
The histological distribution of Cr(VI) within intact human skin was 
studied by Liden and Lundberg (Ex. 35-80). They applied test solutions 
of potassium dichromate in petrolatum or in water as occluded circular 
patches of filter paper to the skin. Results with potassium dichromate 
in water revealed that Cr(VI) penetrated beyond the dermis and 
penetration reached steady state with resorption by the lymph and blood 
vessels by 5 hours. About 10 times more chromium penetrated when 
potassium dichromate was applied in petrolatum than when applied in 
water, indicating that organic solvents facilitate the absorption of 
Cr(VI) from the skin. Baranowska-Dutkiewicz also demonstrated that the 
absorption rates of sodium chromate solutions from the occluded forearm 
skin of volunteers increase with increasing concentration (Ex. 35-75). 
The rates were 1.1 [mu]g Cr(VI)/cm2/hour for a 0.01 molar 
solution, 6.4 [mu]g Cr(VI)/cm2/hour for a 0.1 molar 
solution, and 10 [mu]g Cr(VI)/cm2/hour for a 0.2 molar 
solution.
    Using volunteers, Mali found that potassium dichromate penetrates 
the intact epidermis (Exs. 9-49; 35-41). Wahlberg and Skog demonstrated 
the presence of chromium in the blood, spleen, bone marrow, lymph 
glands, urine and kidneys of guinea pigs exposed to 51 
chromium labeled Cr(VI) compounds (Ex. 35-81). In this study 
radiolabeled sodium chromate solution was dermally applied to guinea 
pigs and 51Cr was monitored by scintillation counting in 
tissues. These studies demonstrate that the absorption of Cr(VI) 
compounds can take place through the dermal route. Also, the absorption 
of Cr(VI) can be facilitated by organic solvents.
4. Absorption of Cr(VI) by the Oral Route
    Inhaled Cr(VI) can enter the digestive tract as a result of 
mucocilliary clearance and swallowing. Studies indicate Cr(VI) is 
absorbed from the gastrointestinal tract. The six-day fecal and 24-hour 
urinary excretion patterns of radioactivity in groups of six volunteers 
given Cr(VI) as sodium chromate labeled with 51chromium 
indicated that at least 2.1% of the Cr(VI) was absorbed. After 
intraduodenal administration at least 10% of the Cr(VI) compound was 
absorbed. These studies also demonstrated that Cr(VI) compounds are 
reduced to Cr(III) compounds in the stomach, thereby accounting for the 
relatively poor gastrointestinal absorption of orally administered 
Cr(VI) compounds (Exs. 35-96; 35-41).
    In the gastrointestinal tract, Cr(VI) can be reduced to Cr(III) by 
gastric juices, which is then poorly absorbed (Underwood, 1971 as cited 
in Ex. 19-1; Ex. 35-85). The mechanism by which Cr(VI) is carried 
across the intestinal wall and the site of absorption are not known and 
may well depend upon the efficiency of defense mechanisms (Mertz, 1969 
as cited in Ex. 19-1).
    Kuykendall et al. studied the absorption of Cr(VI) in human 
volunteers after oral administration of potassium dichromate (Ex. 35-
77). They reported the bioavailability based on 14-day urinary 
excretion to be 6.9% (range 1.2-18%) for Cr(VI). Other investigators 
have also reported absorption of Cr(VI) compounds after oral 
administration (Exs. 35-76; 31-22-13; 35-91).
    Studies with 51chromium in animals also indicate that 
chromium and its compounds are poorly absorbed from the 
gastrointestinal tract after oral exposure. When radioactive sodium 
chromate (Cr(VI)) was given orally to rats, the amount of chromium in 
the feces was greater than that found when sodium chromate was injected 
directly into the small intestine. These results are consistent with 
evidence that the gastric environment has a capacity to reduce Cr(VI) 
to Cr(III) and therefore decrease the amount of Cr(VI) absorbed from 
the GI tract.
    Treatment of rats by gavage with an unencapsulated lead chromate 
pigment or with a silica-encapsulated lead chromate pigment resulted in 
no measurable blood levels of chromium (measured as Cr(III), detection 
limit=10 [mu]g/L) after two or four weeks of treatment or after a two-
week recovery period. However, kidney levels of chromium (measured as 
Cr(III)) were significantly higher in the rats that received the 
unencapsulated pigment when compared to the rats that received the 
encapsulated pigment, indicating that silica encapsulation may reduce 
the gastrointestinal bioavailability of chromium from lead chromate 
pigments (Ex. 11-5). This study does not address the bioavailability of 
encapsulated chromate pigments from the lung where residence time could 
be different.
5. Distribution of Cr(VI) in the Body
    Once in the bloodstream, Cr(VI) is taken up into erythrocytes, 
where it is reduced to lower oxidation states and forms chromium 
protein complexes during reduction (Ex. 35-41). Once complexed with 
protein, chromium cannot leave the cell. The binding of chromium 
compounds by proteins in the blood has been studied in some detail 
(Exs. 5-24; 35-41; 35-52). It was found that intravenously injected 
anionic Cr(VI) passes through the membrane of red blood cells and binds 
to the globin fraction of hemoglobin. It has been hypothesized that 
before Cr(VI) is bound by hemoglobin, it is reduced to Cr(III) by an 
enzymatic reaction within red blood cells. Once inside the blood cell, 
chromium ions are unable to repenetrate the membrane and move back into 
the plasma (Exs. 7-6; 7-7; 19-1; 35-41; 35-52). According to Aaseth et 
al., the intracellular Cr(VI) reduction depletes Cr(VI) concentration 
in the red blood cell (Ex. 35-89). This serves to enhance diffusion of 
Cr(VI) from the plasma into the erythrocyte resulting in very low 
plasma levels of Cr(VI). It is also believed that the rate of uptake of 
Cr(VI) by red blood cells may not exceed the rate at which they reduce 
Cr(VI) to Cr(III) (Ex. 35-99). The higher tissue levels of chromium 
after administration of Cr(VI) than after administration of Cr(III) 
reflect the greater tendency of Cr(VI) to traverse plasma membranes and 
bind to intracellular proteins in the various tissues, which may 
explain the greater degree of toxicity associated with Cr(VI) 
(MacKenzie et al. 1958 as cited in 35-52; Maruyama 1982 as cited in 35-
41; Ex. 35-71).
    Examination of autopsy tissues from chromate workers who were 
occupationally exposed to Cr(VI) showed that the highest chromium 
levels were in the lungs. The liver, bladder, and bone also had 
chromium levels above background. Mancuso examined tissues from three 
individuals with lung cancer who were exposed to chromium in the 
workplace (Ex. 124). One was employed for 15 years as a welder, the 
second and third worked for 10.2 years and 31.8 years, respectively, in 
ore milling and preparations and boiler operations. The cumulative

[[Page 59317]]

chromium exposures for the three workers were estimated to be 3.45, 
4.59, and 11.38 mg/m \3\-years, respectively. Tissues from the first 
worker were analyzed 3.5 years after last exposure, the second worker 
18 years after last exposure, and the third worker 0.6 years after last 
exposure. All tissues from the three workers had elevated levels of 
chromium, with the possible exception of neural tissues. Levels were 
orders of magnitude higher in the lungs when compared to other tissues. 
The highest lung level reported was 456 mg/10 g tissue in the first 
worker, 178 in the second worker, and 1,920 for the third worker. There 
were significant chromium levels in the tissue of the second worker 
even though he had not been exposed to chromium for 18 years. Similar 
results were also reported in autopsy studies of people who may have 
been exposed to chromium in the workplace as well as chrome platers and 
chromate refining workers (Exs. 35-92; 21-1; 35-74; 35-88).
    Animal studies have shown similar distribution patterns after 
inhalation exposure. The distribution of Cr(VI) compared with Cr(III) 
was investigated in guinea pigs after intratracheal instillation of 
potassium dichromate or chromium trichloride (Ex. 7-8). At 24 hours 
after instillation, 11% of the original dose of chromium from potassium 
dichromate remained in the lungs, 8% in the erythrocytes, 1% in plasma, 
3% in the kidney, and 4% in the liver. The muscle, skin, and adrenal 
glands contained only a trace. All tissue concentrations of chromium 
declined to low or nondetectable levels in 140 days, with the exception 
of the lungs and spleen. After chromium trichloride instillation, 69% 
of the dose remained in the lungs at 20 minutes, while only 4% was 
found in the blood and other tissues, with the remaining 27% cleared 
from the lungs and swallowed. The only tissue that contained a 
significant amount of chromium two days after instillation of chromium 
trichloride was the spleen. After 30 and 60 days, 30 and 12%, 
respectively, of the Cr(III) was retained in the lungs, while only 2.6 
and 1.6%, respectively, of the Cr(VI) dose was retained in the lungs.
6. Metabolic Reduction of Cr(VI)
    Cr(VI) is reduced to Cr(III) in the lungs by a variety of reducing 
agents. This serves to limit uptake into lung cells and absorption into 
the bloodstream. Cr(V) and Cr(IV) are transient intermediates in this 
process. The genotoxic effects produced by the Cr(VI) are related to 
the reduction process and are further discussed in the section on 
Mechanistic Considerations.
    In vivo and in vitro experiments in rats indicated that, in the 
lungs, Cr(VI) can be reduced to Cr(III) by ascorbate and glutathione. 
The reduction of Cr(VI) by glutathione is slower than the reduction by 
ascorbate (Ex. 35-65). Other studies have reported the reduction of 
Cr(VI) to Cr(III) by epithelial lining fluid (ELF) obtained from the 
lungs of 15 individuals by bronchial lavage. The average overall 
reduction capacity was 0.6 [mu]g Cr(VI)/mg of ELF protein. In addition, 
cell extracts made from pulmonary alveolar macrophages derived from 
five healthy male volunteers were able to reduce an average of 4.8 
[mu]g Cr(VI)/10 \6\ cells or 14.4 [mu]g Cr(VI)/mg protein (Ex. 35-83). 
Postmitochondrial (S12) preparations of human lung cells (peripheral 
lung parenchyma and bronchial preparations) were also able to reduce 
Cr(VI) to Cr(III) (De Flora et al. 1984 as cited in Ex. 35-41). As 
discussed earlier, Cr(VI) is also reduced to Cr(III) in the gastric 
environment by the gastric juice (Ex. 35-85) and ascorbate after oral 
exposure (Ex. 35-82).
7. Elimination of Cr(VI) From the Body
    Excretion of chromium from Cr(VI) compounds is predominantly in the 
urine, although there is some biliary excretion into the feces. In both 
urine and feces, the chromium is present as low molecular weight 
Cr(III) complexes. Absorbed chromium is excreted from the body in a 
rapid phase representing clearance from the blood and at least two 
slower phases representing clearance from tissues. Urinary excretion 
accounts for over 50% of eliminated chromium (Ex. 35-41). Although 
chromium is excreted in urine and feces, the intestine plays only a 
minor part in chromium elimination, representing only about 5% of 
elimination from the blood (Ex. 19-1). Normal urinary levels of 
chromium in humans have been reported to range from 0.24-1.8 [mu]g/L 
with a median level of 0.4 [mu]g/L (Ex. 35-79). Humans exposed to 0.05-
1.7 mg Cr(III)/m \3\ as chromium sulfate and 0.01-0.1 mg Cr(VI)/m \3\ 
as potassium dichromate (8-hour time-weighted average) had urinary 
excretion levels from 0.0247 to 0.037 mg Cr(III)/L. Workers exposed 
mainly to Cr(VI) compounds had higher urinary chromium levels than 
workers exposed primarily to Cr(III) compounds. An analysis of the 
urine did not detect Cr(VI), indicating that Cr(VI) was rapidly reduced 
before excretion (Exs. 35-294; 5-48).
    A half-life of 15-41 hours has been estimated for chromium in urine 
for four welders using a linear one-compartment kinetic model (Exs. 35-
73; 5-52; 5-53). Limited work on modeling the absorption and deposition 
of chromium indicates that adipose and muscle tissue retain chromium at 
a moderate level for about two weeks, while the liver and spleen store 
chromium for up to 12 months. The estimated half-life for whole body 
chromium retention is 22 days for Cr(VI) and 92 days for Cr(III) (Ex. 
19-1). The half-life of chromium in the human lung is 616 days, which 
is similar to the half-life in rats (Ex. 7-5).
    Elimination of chromium was shown to be very slow in rats exposed 
to 2.1 mg Cr(VI)/m \3\ as zinc chromate six hours/day for four days. 
Urinary levels of chromium remained almost constant for four days after 
exposure and then decreased (Ex. 35-93). After intratracheal 
administration of sodium dichromate to rats, peak urinary chromium 
concentrations were observed at six hours, after which the urinary 
concentrations declined rapidly (Ex. 35-94). The more prolonged 
elimination of the less soluble zinc chromate as compared to the more 
soluble sodium dichromate is consistent with the influence of Cr(VI) 
solubility on absorption from the respiratory tract discussed earlier.
    Information regarding the excretion of chromium in humans after 
dermal exposure to chromium or its compounds is limited. Fourteen days 
after application of a salve containing potassium chromate, which 
resulted in skin necrosis and sloughing at the application site, 
chromium was found at 8 mg/L in the urine and 0.61 mg/100 g in the 
feces of one individual (Brieger 1920 as cited in Ex. 19-1). A slight 
increase over background levels of urinary chromium was observed in 
four subjects submersed in a tub of chlorinated water containing 22 mg 
Cr(VI)/L as potassium dichromate for three hours (Ex. 31-22-6). For 
three of the four subjects, the increase in urinary chromium excretion 
was less than 1 [mu]g/day over the five-day collection period. Chromium 
was detected in the urine of guinea pigs after radiolabeled sodium 
chromate solution was applied to the skin (Ex. 35-81).
8. Physiologically-based Pharmacokinetic Modeling
    O'Flaherty developed physiologically-based pharmacokinetic (PBPK) 
models that simulate absorption, distribution, metabolism, and 
excretion of Cr(VI) and Cr(III) compounds in humans (Ex. 35-95) and 
rats (Exs. 35-86; 35-70). The original model (Ex. 35-86) evolved from a 
similar model for lead, and contained compartments for the lung, GI 
tract, skin, blood, liver, kidney, bone, well-

[[Page 59318]]

perfused tissues, and slowly perfused tissues. The model was refined to 
include two lung subcompartments for chromium, one of which allowed 
inhaled chromium to enter the blood and GI tract and the other only 
allowed chromium to enter the GI tract (Ex. 35-70). Reduction of Cr(VI) 
to Cr(III) was considered to occur in every tissue compartment except 
bone.
    The model was developed from several data sets in which rats were 
dosed with Cr(VI) or Cr(III) intravenously, orally or by intratracheal 
instillation, because different distribution and excretion patterns 
occur depending on the route of administration. In most cases, the 
model parameters (e.g., tissue partitioning, absorption, reduction 
rates) were estimated by fitting model simulations to experimental 
data. The optimized rat model was validated against the 1978 Langard 
inhalation study (Ex. 35-93). Chromium blood levels were overpredicted 
during the four-day inhalation exposure period, but blood levels during 
the post-exposure period were well predicted by the model. The model-
predicted levels of liver chromium were high, but other tissue levels 
were closely estimated.
    A human PBPK model recently developed by O'Flaherty et al. is able 
to predict tissue levels from ingestion of Cr(VI) (Ex. 35-95). The 
model incorporates differential oral absorption of Cr(VI) and Cr(III), 
rapid reduction of Cr(VI) to Cr(III) in major body fluids and tissues, 
and concentration-dependent urinary clearance. The model does not 
include a physiologic lung compartment, but can be used to estimate an 
upper limit on pulmonary absorption of inhaled chromium. The model was 
calibrated against blood and urine chromium concentration data from a 
group of controlled studies in which adult human volunteers drank 
solutions of soluble Cr(III) or Cr(VI).
    PBPK models are increasingly used in risk assessments, primarily to 
predict the concentration of a potentially toxic chemical that will be 
delivered to any given target tissue following various combinations of 
route, dose level, and test species. Further development of the 
respiratory tract portion of the model, specific Cr(VI) rate data on 
extracellular reduction and uptake into lung cells, and more precise 
understanding of critical pathways inside target cells would improve 
the model value for risk assessment purposes.
9. Summary
    Based on the studies presented above, evidence exists in the 
literature that shows Cr(VI) can be systemically absorbed by the 
respiratory tract. The absorption of inhaled chromium compounds depends 
on a number of factors, including physical and chemical properties of 
the particles (oxidation state, size, and solubility), the reduction 
capacity of the ELF and alveolar macrophages and clearance by the 
mucocliary escalator and phagocytosis. Soluble Cr(VI) compounds enter 
the bloodstream more readily than highly insoluble Cr(VI) compounds. 
However, insoluble compounds may have longer residence time in lung. 
Absorption of Cr(VI) can also take place after oral and dermal 
exposure, particularly if the exposures are high.
    The chromate (CrO4)2- enters cells via 
facilitated diffusion through non-specific anion channels (similar to 
phosphate and sulfate anions). Following absorption of Cr(VI) compounds 
from various exposure routes, chromium is taken up by the blood cells 
and is widely distributed in tissues as Cr(VI). Inside blood cells and 
tissues, Cr(VI) is rapidly reduced to lower oxidation states and bound 
to macromolecules which may result in genotoxic or cytotoxic effects. 
However, in the blood a substantial proportion of Cr(VI) is taken up 
into erythrocytes, where it is reduced to Cr(III) and becomes bound to 
hemoglobin and other proteins.
    Inhaled Cr(VI) is reduced to Cr(III) in vivo by a variety of 
reducing agents. Ascorbate and glutathione in the ELF and macrophages 
have been shown to reduce Cr(VI) to Cr(III) in the lungs. After oral 
exposure, gastric juices are also responsible for reducing Cr(VI) to 
Cr(III). This serves to limit the amount of Cr(VI) systemically 
absorbed.
    Absorbed chromium is excreted from the body in a rapid phase 
representing clearance from the blood and at least two slower phases 
representing clearance from tissues. Urinary excretion is the primary 
route of elimination, accounting for over 50% of eliminated chromium. 
Although chromium is excreted in urine and feces, the intestine plays 
only a minor part in chromium elimination representing only about 5% of 
elimination from the blood.

B. Carcinogenic Effects

    There has been extensive study on the potential for Cr(VI) to cause 
carcinogenic effects, particularly cancer of the lung. OSHA reviewed 
epidemiologic data from several industry sectors including chromate 
production, chromate pigment production, chromium plating, stainless 
steel welding, and ferrochromium production. Supporting evidence from 
animal studies and mechanistic considerations are also evaluated in 
this section.
1. Evidence from Chromate Production Workers
    The epidemiologic literature of workers in the chromate production 
industry represents the earliest and best-documented relationship 
between exposure to chromium and lung cancer. The earliest study of 
chromate production workers in the United States was reported by Machle 
and Gregorius in 1948 (Ex.7-2). In the United States, two chromate 
production plants, one in Baltimore, Maryland and one in Painesville, 
Ohio have been the subject of multiple studies. Both plants were 
included in the 1948 Machle and Gregorius study and again in the study 
conducted by the Public Health Service and published in 1953 (Ex. 7-3). 
Both of these studies reported the results in aggregate. The Baltimore 
chromate production plant was studied by Hayes et al. (Ex. 7-14) and 
more recently by Gibb et al. (Ex. 31-22-11). The chromate production 
plant in Painesville, Ohio has been followed since the 1950s by Mancuso 
with his most recent follow-up published in 1997. The most recent study 
of the Painesville plant was published by Luippold et al. (Ex. 31-18-
4). The studies by Gibb and Luippold present historical exposure data 
for the time periods covered by their respective studies. The Gibb 
exposure data are especially interesting since the industrial hygiene 
data were collected on a routine basis and not for compliance purposes. 
These routine air measurements may be more representative of those 
typically encountered by the exposed workers. In Great Britain, three 
plants have been studied repeatedly, with reports published between 
1952 and 1991. Other studies of cohorts in the United States, Germany, 
Italy and Japan are also reported. The consistently elevated lung 
cancer mortality reported in these cohorts and the significant upward 
trends with duration of employment and cumulative exposure provide some 
of the strongest evidence that Cr(VI) be regarded as carcinogenic to 
workers. A summary of selected human epidemiologic studies in chromate 
production workers is presented in Table VI-1.

[[Page 59319]]



Table VI-1.--Summary of Selected Epidemiologic Studies of Lung Cancer in Workers Exposed to Hexavalent Chromium--
                                               Chromate Production
----------------------------------------------------------------------------------------------------------------
                                                           Reference         Chromium (VI)
    Reference/exhibit number       Study population       population           exposure        Lung Cancer Risk
----------------------------------------------------------------------------------------------------------------
Hayes et al. (1979, Ex. 7-14)...  1803 male workers   Baltimore City      Primarily sodium    --O/E of 2.0
Braver et al. (1985, Ex. 7-17)..   initially           mortality.          chromate and        (p< 0.01) based on
                                   employed 3 or                           dichromate          59 lung cancer
                                   more months 1945-                       production. Avg     deaths.
                                   1974 at old and                         Cr(VI) of 21 to    --Increased risk
                                   new Baltimore MD                        413 [mu]g/m\3\      with duration of
                                   production                              and avg duration    employment.
                                   facility; follow-                       1.6 yr to 13 yr
                                   up through 1977.                        depending on
                                                                           subcohort, plant,
                                                                           and year employed.
Gibb et al. (2000, Ex. 31-22-11)  2357 male workers   U.S. mortality....  Primarily sodium    --O/E of 1.86
                                   initially                               chromate and        (p< 0.01) based on
                                   employed 1950-                          dichromate. Mean    71 lung cancer
                                   1974 only at new                        cumulative Cr(VI)   deaths.
                                   Baltimore MD                            of 0.070 mg/m\3\ - --Significant
                                   production                               yr and work        upward mortality
                                   facility; follow-                       duration of 3.1     trend with
                                   up through 1992.                        yr.                 cumulative Cr(VI)
                                                                                               exposure.
Mancuso (1997, Ex. 23)..........  332 male workers    Mortality rate      Primarily sodium    O/E not calculated
Mancuso (1975, Ex. 7-11)........   employed at         directly            chromate and        but significant
Mancuso and Heuper (1951, Ex. 7-   Painesville OH      calculated using    dichromate          increase in age-
 13)..                             facility 1931-      the distribution    production with     adjusted lung
Bourne and Yee (1950, Ex. 7-98).   1937; follow-up     of person years     some calcium        cancer death rate
                                   through 1993.       by age group for    chromate as a       with cumulative
                                                       the entire          result of using     chromium exposure
                                                       exposed             high lime           based on 66
                                                       population as the   process. Most       deaths.
                                                       standard.           cumulative
                                                                           soluble Cr(VI)
                                                                           between 0.25 and
                                                                           4.0 mg/m\3\ - yr
                                                                           based on 1949
                                                                           survey.
Luippold et al. (2003, Ex. 31-18- 492 male workers    U.S. and Ohio       Primarily sodium    --O/E of
 4).                               employed one year   Mortality Rates.    chromate and        2.41(p< 0.01)
                                   between 1940 and                        dichromate          based on Ohio
                                   1972 at                                 production with     rates and 51
                                   Painesville OH                          minor calcium       deaths.
                                   facility; follow-                       chromate. Mean     --Significant
                                   up through 1997.                        cumulative          upward mortality
                                                                           soluble Cr(VI) of   trend with
                                                                           1.58 mg/m\3\ - yr.  cumulative Cr(VI)
                                                                                               exposure
Davies et al. (1991, Ex. 7-99)..  2298 male chromate  Cancer mortality    Principally sodium  --O/E of 1.97
Alderson et al. (1981, Ex. 7-      production          of England, Wales   chromate and        (p< 0.01) pre-
 22)..                             workers employed    and Scotland and    dichromate          process change
Bistrup and Case (1956, Ex. 7-     for one year        unexposed local     production with     based on 175
 20)..                             between 1950 and    workers.            some calcium        deaths.
                                   1976 at three                           chromate before    --SMR of 1.02 (NS)
                                   different UK                            switch from high    post-process
                                   plants; follow-up                       lime to no lime     change based on
                                   through 1989.                           process. Avg        14 deaths.
                                                                           soluble Cr(VI) in  --Increased risk
                                                                           early 1950s from    for high exposed
                                                                           2 to 880 [mu]g/     compared with
                                                                           m\3\ depending on   less exposed.
                                                                           job.
Korallus et al. (1993, Ex. 7-     1417 chromate       Mortality rates     Principally sodium  --O/E of 2.27
 91)..                             production          for North Rhine-    chromate and        (p< 0.01) pre-
Korallus et al. (1982, Ex. 7-      workers employed    Westphalia region   dichromate          process change
 26)..                             for one year        of Germany where    production with     based on 66
                                   between 1948 and    plants located.     some calcium        deaths.
                                   1987 at two                             chromate before    --O/E of 1.25 (NS)
                                   different German                        switch from high    post-process
                                   plants; follow-up                       lime to no lime     change based on 9
                                   through 1988.                           process. Annual     deaths.
                                                                           mean Cr(VI)
                                                                           between 6.2 and
                                                                           38 [mu]g/m\3\
                                                                           after 1977.
                                                                           Cr(VI) exposure
                                                                           not reported
                                                                           before 1977.
----------------------------------------------------------------------------------------------------------------
Observed/Expected (O/E)
Relative Risk (RR)
Not Statistically Significant (NS)
Odds Ratio (OR)

    The basic hexavalent chromate production process involves milling 
and mixing trivalent chromite ore with soda ash, sometimes in the 
presence of lime (Exs. 7-103; 35-61). The mixture is ``roasted'' at a 
high temperature, which oxidizes much of the chromite to hexavalent 
sodium chromate. Depending on the lime content used in the process, the 
roast also contains other chromate species, especially calcium chromate 
under high lime conditions. The highly water-soluble sodium chromate is 
water-extracted from the water-insoluble trivalent chromite and the 
less water-soluble chromates (e.g., calcium chromate) in the 
``leaching'' process. The sodium chromate leachate is reacted with 
sulfuric acid and sodium bisulfate to form sodium dichromate. The 
sodium dichromate is prepared and packaged as a crystalline powder to 
be sold as final product or sometimes used as the starting material to 
make other chromates such as chromic acid and potassium dichromate.
    a. Cohort Studies of the Baltimore Facility. The Hayes et al. study 
of the Baltimore, Maryland chromate production plant was designed to 
determine whether changes in the industrial process at one chromium 
chemical production facility were associated with a decreased risk of 
cancer, particularly cancer of the respiratory system (Ex. 7-14). Four 
thousand two hundred and seventeen (4,217) employees were identified as 
newly employed between January 1, 1945 and December 31, 1974. Excluded 
from this initial enumeration were employees who: (1) were working as 
of 1945, but had been hired prior to 1945 and (2) had been hired since 
1945 but who had previously been employed at the plant. Excluded from 
the final cohort were those employed less than 90 days; women; those 
with unknown length of employment; those with no work history; and 
those of unknown age. The final cohort included 2,101 employees (1,803 
hourly and 298 salaried).
    Hayes divided the production process into three departments: (1) 
The mill and roast or ``dry end'' department which consists of 
grinding, roasting and leaching processes; (2) the bichromate 
department which consists of the acidification and crystallization 
processes; and (3) the special products department which produces 
secondary products including chromic acid. The bichromate and special 
products departments are referred to as the ``wet end''.
    The construction of a new mill and roast and bichromate plant that 
opened during 1950 and 1951 and a new chromic acid and special products 
plant that opened in 1960 were cited by Hayes as ``notable production 
changes'' (Ex. 7-

[[Page 59320]]

14). The new facilities were designed to ``obtain improvements in 
process technique and in environmental control of exposure to chromium 
bearing dusts * * *'' (Ex. 7-14).
    Plant-related work and health histories were abstracted for each 
employee from plant records. Each job on the employee's work history 
was characterized according to whether the job exposure occurred in (1) 
a newly constructed facility, (2) an old facility, or (3) could not be 
classified as having occurred in the new or the old facility. Those who 
ever worked in an old facility or whose work location(s) could not be 
distinguished based upon job title were considered as having a high or 
questionable exposure. Only those who worked exclusively in the new 
facility were defined for study purposes as ``low exposure''. Data on 
cigarette smoking was abstracted from plant records, but was not 
utilized in any analyses since the investigators thought it ``not to be 
of sufficient quality to allow analysis.''
    One thousand one hundred and sixty nine (1,169) cohort members were 
identified as alive, 494 not individually identified as alive and 438 
as deceased. Death certificates could not be located for 35 reported 
decedents. Deaths were coded to the 8th revision of the International 
Classification of Diseases.
    Mortality analysis was limited to the 1,803 hourly employees 
calculating the standardized mortality ratios (SMRs) for specific 
causes of death. The SMR is a ratio of the number of deaths observed in 
the study population to the number that would be expected if that study 
population had the same specific mortality rate as a standard reference 
population (e.g., age-, gender-, calendar year adjusted U.S. 
population). The SMR is typically multiplied by 100, so a SMR greater 
than 100 represents an elevated mortality in the study cohort relative 
to the reference group. In the Hayes study, the expected number of 
deaths was based upon Baltimore, Maryland male mortality rates 
standardized for age, race and time period. For those where race was 
unknown, the expected numbers were derived from mortality rates for 
whites. Cancer of the trachea, bronchus and lung accounted for 69% of 
the 86 cancer deaths identified and was statistically significantly 
elevated (O = 59; E = 29.16; SMR = 202; 95% CI: 155-263).
    Analysis of lung cancer deaths among hourly workers by year of 
initial employment (1945-1949; 1950-1959 and 1960-1974), exposure 
category (low exposure or questionable/high exposure) and duration of 
employment (short term defined as 90 days-2 years; long term defined as 
3 years +) was also conducted. For those workers characterized as 
having questionable/high exposure, the SMRs were significantly elevated 
for the 1945-1949 and the 1950-1959 hire periods and for both short- 
and long-term workers (not statistically significant for the short-term 
workers initially hired 1945-1949). For those characterized as low 
exposure, there was an elevated SMR for the long-term workers hired 
between 1950 and 1959, but based only on three deaths (not 
statistically significant). No lung cancer cases were observed for 
workers hired 1960-1974.
    Case-control analyses of (1) a history of ever having been employed 
in selected jobs or combinations of jobs or (2) a history of specified 
morbid conditions and combinations of conditions reported on plant 
medical records were conducted. Cases were defined as decedents (both 
hourly and salaried were included in the analyses) whose underlying or 
contributing cause of death was lung cancer. Controls were defined as 
deaths from causes other than malignant or benign tumors. Cases and 
controls were matched on race (white/non-white), year of initial 
employment (+/-3 years), age at time of initial employment (+/-5 years) 
and total duration of employment (90 days-2 years; 3-4 years and 5 
years +). An odds ratio (OR) was determined where the ratio is the odds 
of employment in a job involving Cr(VI) exposure for the cases relative 
to the controls.
    Based upon matched pairs, analysis by job position showed 
significantly elevated odds ratios for special products (OR = 2.6) and 
bichromate and special products (OR = 3.3). The relative risk for 
bichromate alone was also elevated (OR = 2.1, not statistically 
significant).
    The possible association of lung cancer and three health conditions 
(skin ulcers, nasal perforation and dermatitis) as recorded in the 
plant medical records was also assessed. Of the three medical 
conditions, only the odds ratio for dermatitis was statistically 
significant (OR = 3.0). When various combinations of the three 
conditions were examined, the odds ratio for having all three 
conditions was statistically significantly elevated (OR = 6.0).
    Braver et al. used data from the Hayes study discussed above and 
the results of 555 air samples taken during the period 1945-1950 by the 
Baltimore City Health Department, the U.S. Public Health Service, and 
the companies that owned the plant, in an attempt to examine the 
relationship between exposure to Cr(VI) and the occurrence of lung 
cancer (Ex. 7-17). According to the authors, methods for determining 
the air concentrations of Cr(VI) have changed since the industrial 
hygiene data were collected at the Baltimore plant between 1945 and 
1959. The authors asked the National Institute for Occupational Safety 
and Health (NIOSH) and the Occupational Safety and Health 
Administration (OSHA) to review the available documents on the methods 
of collecting air samples, stability of Cr(VI) in the sampling media 
after collection and the methods of analyzing Cr(VI) that were used to 
collect the samples during that period.
    Air samples were collected by both midget impingers and high volume 
samplers. According to the NIOSH/OSHA review, high volume samplers 
could have led to a ``significant'' loss of Cr(VI) due to the reduction 
of Cr(VI) to Cr(III) by glass or cellulose ester filters, acid 
extraction of the chromate from the filter, or improper storage of 
samples. The midget impinger was ``less subject'' to loss of Cr(VI) 
according to the panel since neither filters nor acid extraction from 
filters was employed. However, if iron was present or if the samples 
were stored for too long, conversion from Cr(VI) to Cr(III) may have 
occurred. The midget impinger can only detect water soluble Cr(VI). The 
authors noted that, according to a 1949 industrial hygiene survey by 
the U.S. Public Health Service, very little water insoluble Cr(VI) was 
found at the Baltimore plant. One NIOSH/OSHA panel member characterized 
midget impinger results as ``reproducible'' and ``accuracy * * * fairly 
solid unless substantial reducing agents (e.g., iron) are present'' 
(Ex. 7-17, p. 370). Based upon the panel's recommendations, the authors 
used the midget impinger results to develop their exposure estimates 
even though the panel concluded that the midget impinger methods ``tend 
toward underestimation'' of Cr(VI).
    The authors also cite other factors related to the industrial 
hygiene data that could have potentially influenced the accuracy of 
their exposure estimates (either overestimating or underestimating the 
exposure). These include: measurements may have been taken primarily in 
``problem'' areas of the plant; the plants may have been cleaned or 
certain processes shut down prior to industrial hygiene monitoring by 
outside groups; respirator use; and periodic high exposures (due to 
infrequent maintenance operations or failure of exposure control 
equipment) which were not measured and therefore not reflected in the 
available data.
    The authors estimated exposure indices for cohorts rather than for 
specific individuals using hire period (1945-1949 or 1950-1959) and 
duration

[[Page 59321]]

of exposure, defined as short (at least 90 days but less than three 
years) and long (three years or more). The usual exposure to Cr(VI) for 
both the short- and long-term workers hired 1945-1949 was calculated as 
the average of the mean annual air concentration for 1945-1947 and 1949 
(data were missing for 1948). This was estimated to be 413 [mu]g/m\3\. 
The usual exposure to Cr(VI) was estimated to be 218 [mu]g/m\3\ for the 
short and long employees hired between 1950 and 1959 based on air 
measurements in the older facility in the early 1950s.
    Cumulative exposure was calculated as the usual exposure level x 
average duration. Short-term workers, regardless of length of 
employment, were assumed to have received 1.6 years of exposure 
regardless of hire period. For long-term workers, the average length of 
exposure was 12.3 years. Those hired 1945-1949 were assigned five years 
at an exposure of 413 [mu]g/m\3\ and 7.3 years at an exposure of 218 
[mu]g/m\3\. For the long-term workers hired 1950-1959, the average 
length of exposure was estimated to be 13.4 years. The authors 
estimated that the cumulative exposures at which ``significant 
increases in lung cancer mortality'' were observed in the Hayes study 
were 0.35, 0.67, 2.93 and 3.65 [mu]g/m\3\-years. The association seen 
by the authors appears more likely to be the result of duration of 
employment rather than the magnitude of exposure since the variation in 
the latter was small.
    Gibb et al. relied upon the Hayes study to investigate mortality in 
a second cohort of the Baltimore plant (Ex. 31-22-11). The Hayes cohort 
was composed of 1,803 hourly and 298 salaried workers newly employed 
between January 1, 1945 and December 31, 1974. Gibb excluded 734 
workers who began work prior to August 1, 1950 and included 990 workers 
employed after August 1, 1950 who worked less than 90 days, resulting 
in a cohort of 2,357 males followed for the period August 1, 1950 
through December 31, 1992. Fifty-one percent (1,205) of the cohort was 
white; 36% (848) nonwhite. Race was unknown for 13% (304) of the 
cohort. The plant closed in 1985.
    Deaths were coded according to the 8th revision of the 
International Classification of Diseases. Person years of observation 
were calculated from the beginning of employment until death or 
December 31, 1992, whichever came earlier. Smoking data (yes/no) were 
available for 2,137 (93.3%) of the cohort from company records.
    Between 1950 and 1985, approximately 70,000 measurements of 
airborne Cr(VI) were collected utilizing several different sampling 
methods. The program of routine air sampling for Cr(VI) was initiated 
to ``characterize `typical/usual exposures' of workers'' (Ex. 31-22-11, 
p.117). Area samples were collected during the earlier time periods, 
while both area and personal samples were collected starting in 1977. 
Exposure estimates were derived from the area sampling systems and were 
adjusted to ``an equivalent personal exposure estimate using job-
specific ratios of the mean area and personal sampling exposure 
estimates for the period 1978-1985 * * *.'' (Ex. 31-22-11, p.117). 
According to the author, comparison of the area and personal samples 
showed ``no significant differences'' for about two-thirds of the job 
titles. For several job titles with a ``significant point source of 
contamination'' the area sampling methods ``significantly 
underestimated'' personal exposure estimates and were adjusted ``by the 
ratio of the two'' (Ex. 31-22-11, p.118).
    A job exposure matrix (JEM) was constructed, where air sampling 
data were available, containing annual average exposure for each job 
title. Data could not be located for the periods 1950-1956 and 1960-
1961. Exposures were modeled for the missing data using the ratio of 
the measured exposure for a job title to the average of all measured 
job titles in the same department. For the time periods where 
``extensive'' data were missing, a simple straight line interpolation 
between years with known exposures was employed.
    In an attempt to estimate airborne Cr(III) concentrations, 72 
composite dust samples were collected at or near the fixed site air 
monitoring stations about three years after the facility closed. The 
dust samples were analyzed for Cr(VI) content using ion chromatography. 
Cr(III) content was determined through inductively coupled plasma 
spectroscopic analysis of the residue. The Cr(III):Cr(VI) ratio was 
calculated for each area corresponding to the air sampling zones and 
the measured Cr(VI) air concentration adjusted based on this ratio. 
Worker exposures were calculated for each job title and weighted by the 
fraction of time spent in each air-monitoring zone. The Cr(III):Cr(VI) 
ratio was derived in this manner for each job title based on the 
distribution of time spent in exposure zones in 1978. Cr(VI) exposures 
in the JEM were multiplied by this ratio to estimate Cr(III) exposures.
    A total of 855 observed deaths (472 white; 323 nonwhite and 60 race 
unknown) were reported. SMRs were calculated using U.S. rates for 
overall mortality. Maryland rates (the state in which the plant was 
located) were used to analyze lung cancer mortality in order to better 
account for regional differences in disease fatality.
    A statistically significant lung cancer SMR, based on the national 
rate, was found for whites (O=71; SMR=186; 95% CI: 145-234); nonwhites 
(O=47; SMR=188; 95% CI: 138-251) and the total cohort (O=122; SMR=180; 
95% CI: 149-214). Of the 122 lung cancer cases, 116 were smokers and 
four were non smokers at the time of hire. Smoking status was unknown 
for two lung cancer cases. SMRs were not adjusted for smoking.
    The ratio of observed to expected lung cancer deaths (O/E) for the 
entire cohort stratified by race and cumulative exposure quartile were 
computed. Cumulative exposure was lagged five years (only exposure 
occurring five years before a given age was counted). The cut point for 
the quartiles divided the cohort into four equal groups based upon 
their cumulative exposure at the end of their working history (0-
0.00149 mgCrO3/m3-yr; 0.0015-0.0089 
mgCrO3/m3-yr; 0.009-0.0769 mgCrO3/
m3-yr; and 0.077-5.25 mgCrO3/m3-yr). 
For whites, the relative risk of lung cancer was significantly elevated 
for the second through fourth exposure quartiles with O/E values of 
0.8, 2.1, 2.1 and 1.7 for the four quartiles, respectively. For 
nonwhites, the O/E values by exposure quartiles were 1.1, 0.9, 1.2 and 
2.9, respectively. Only the highest exposure quartile was significantly 
elevated. For the total cohort, a significant exposure-response trend 
was observed such that lung cancer mortality increased with increasing 
cumulative Cr(VI) exposure.
    Proportional hazards models were used to assess the relationship 
between chromium exposure and the risk of lung cancer. The lowest 
exposure quartile was used as the reference group. The median exposure 
in each quartile was used as the measure of cumulative Cr(VI) exposure. 
When smoking status was included in the model, relative lung cancer 
risks of 1.83, 2.48 and 3.32 for the second, third and fourth exposure 
quartiles respectively were estimated. Smoking, Cr(III) exposure, and 
work duration were also significant predictors of lung cancer risk in 
the model.
    The analysis attempted to separate the effects into two 
multivariate proportionate hazards models (one model incorporated the 
log of cumulative Cr(VI) exposure, the log of cumulative Cr(III) 
exposure and smoking; the second incorporated the log of cumulative 
Cr(VI), work duration and smoking). In either regression model, lung 
cancer mortality remained significantly associated (p <  .05) with

[[Page 59322]]

cumulative Cr(VI) exposure even after controlling for the combination 
of smoking and Cr(III) exposure or the combination of smoking and work 
duration. On the other hand, lung cancer mortality was not 
significantly associated with cumulative Cr(III) or work duration in 
the multivariate analysis indicating lung cancer risk was more strongly 
correlated with cumulative Cr(VI) exposure than the other variables.
    Exponent, as part of a larger submission from the Chrome Coalition, 
submitted comments on the Gibb paper asking that OSHA review 
methodological issues believed by Exponent to impact upon the 
usefulness of the Gibb data in a risk assessment analysis. While 
Exponent states that the Gibb study offers data that ``are 
substantially better for cancer risk than the Mancuso study* * *'' they 
believe that further scrutiny of some of the methods and analytical 
procedures are necessary (Ex. 31-18-15-1, p. 5).
    The issues raised by Exponent and the Chrome Coalition (Ex. 31-18-
14) concerning the Gibb paper are: selection of the appropriate 
reference population for compilation of expected numbers for use in the 
SMR analysis; inclusion of short term workers (< 1 year); expansion of 
the number of exposure groupings to evaluate dose response trends; 
analyzing dose response by peak JEM exposure levels; analyzing dose-
response at exposures above and below the current PEL and calculating 
smoking-adjusted SMRs for use in dose-response assessments. Exponent 
obtained the original data from the Gibb study. The data were 
reanalyzed to address the issues cited above. Exponent's findings are 
presented in Exhibit 31-18-15-1 and are discussed below.
    Exponent suggests that Gibb's use of U.S. and Maryland mortality 
rates for developing expectations for the SMR analysis was 
inappropriate and suggested that Baltimore city mortality rates would 
have been the appropriate standard to select since those mortality 
rates would more accurately reflect the mortality experience of those 
who worked at the plant. Exponent reran the SMR analysis to compare the 
SMR values reported by Gibb (U.S. mortality rates for SMR analysis) 
with the results of an SMR analysis using Maryland mortality rates and 
Baltimore mortality rates. Gibb reported a lung cancer SMR of 1.86 (95% 
CI: 1.45-2.34) for white males based upon 71 lung cancer deaths using 
U.S. mortality rates. Reanalysis of the data produced a lung cancer SMR 
of 1.85 (95% CI: 1.44-2.33) for white males based on U.S. mortality 
rates, roughly the same value obtained by Gibb. When Maryland and 
Baltimore rates are used, the SMR drops to 1.70 and 1.25 respectively.
    Exponent suggested conducting sensitivity analysis that excludes 
short-term workers (defined as those with one year of employment) since 
the epidemiologic literature suggests that the mortality of short-term 
workers is different than long-term workers. Short-term workers in the 
Gibb study comprise 65% of the cohort and 54% of the lung cancers. The 
Coalition also suggested that data pertaining to short-term employee's 
information are of ``questionable usefulness for assessing the 
increased cancer risk from chronic occupational exposure to Cr(VI)'' 
(Ex. 31-18-15-1, p. 5).
    Lung cancer SMRs were calculated for those who worked < 1 year and 
for those who worked one year or more. Exponent defined short-term 
workers as those who work