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Occupational Toxicology

Although a number of U.S. organizations develop occupational exposure limits (OELs), much of the effort has focused on a relatively small subset of high volume chemicals, or those with particularly severe toxic end points. As a result, many workers are exposed to substances for which no guidance on acceptable exposure levels has been developed. The shortfall in protection of worker health due to the limited number of OELs suggests that active participation by TERA in this area is consistent with our mission to use the best available science for development of risk values to protect public health. TERA’s goal is to work cooperatively with other organizations’ efforts to see that more OELs are developed and take full advantage of advances in risk assessment methods.

Expanding the current coverage of OELs is valuable to companies and in the public interest because it:

  • Enhances Product Stewardship efforts by providing more complete health and safety guidance to product users.
  • Promotes risk communication by informing workers of potential adverse effects of chemical exposure.
  • Provides a scientific basis for evaluating whether existing environmental control technologies are adequate.

TERA works to support OEL development through two distinct programs: development of sound OELs by TERA staff, and organizing independent peer reviews of values developed by others.

Development of OELs and Documentation
We develop new OELs for chemicals of interest to you and your company or agency. To develop an OEL for you, we perform a comprehensive review and evaluation of the scientific literature and derive occupational values based on sound science and state-of-the-art risk assessment methods.

Independent Peer Review of OELs
An essential element in the acceptance of newly derived risk values is a scientific peer review. TERA’s Peer Review program provides a forum for independent scientific peer review of OELs developed by industry or government. TERA peer reviews bring together scientists from academic, government, and industry backgrounds providing a balanced review by experts in the fields of toxicology, occupational health, and risk assessment.

Selected TERA Projects in Occupational Toxicology

TERA has diverse corporate experience in supporting the occupational toxicology needs of our project sponsors.  Below are descriptions of recent projects.

  • Screening Level OELs.  For a private sponsor evaluated available toxicology data and developed equipment cleaning validation limits and screening level OELs for pharmaceutical ingredients.  
  • Bromopropane – an analysis of issues and considerations for developing an occupational exposure limit for 1-bromopropane was developed.  The analysis relied on benchmark concentration modeling and consideration of neurological versus reproductive toxicity as alternative critical endpoints.  Link to Document
  • IDLH – Immediately Dangerous to Life or Health (IDLH) values are 30-minute airborne concentrations developed to protect against severe irreversible effects or effects that might impair escape from exposure environments should respiratory protection or other control measures fail.  IDLH methods research and documentation supporting new values are being developed.
  • Scientific Criteria for Deriving Occupational Exposure Limits.  In a project sponsored by the International Council on Mining and Metals, authored a manuscript providing a critical analysis of the scientific criteria for deriving occupational exposure levels. 
  • Comparative Health Hazard Ranking.  For a private sponsor, surveyed available health hazard ranking tools and methods, and provided a comparative analysis of selected systems for 12 substances for occupational and consumer exposure scenarios.
  • Risk Thresholds of Concern.  For a private sponsor coauthored a report on the basis for setting risk assessment dose thresholds for occupational exposure to products for which full toxicity data are not available. 
  • Health and Safety Clearance of Chemicals.  For a private sponsor developed a framework for conducting screening level risk assessments for chemicals newly introduced to facility operations.  Won the “Best Risk Assessment Poster” at AIHC&E. 
  • Job Safety Analysis.  For the Cincinnati Parks Department, developed a health hazards summary and reviewed a job safety analysis for pruning of cacti that emit phorbol ester compounds.  For a research university developed a database tool and protocol for evaluating laboratory safety procedures.
  • Metal Refining Process Hazards.  For a private sponsor, conducted a comprehensive toxicology and industrial hygiene review for a refining operation.
  • Dermal –  a project is underway to apply the National Institute for Occupational Safety and Health’s weight of evidence procedures to assign notations that inform workers of potential systemic toxicity, direct skin effects, and sensitization potential from dermal exposures to chemicals. View Poster
  • Diacetyl – A toxicology review and issues analysis related to the availability of data to support OEL development for the butter-flavoring chemical, diacetyl, is under development.  In particular, evaluation of issues related to interspecies extrapolation and effects of peak versus cumulative exposure are being considered. View Presentation 
  • HPV, REACH, and screening Assessments – TERA provides support to a variety of sponsors in cataloging, critically evaluating, and developing robust data summaries, test plans, and risk assessment documents.  We apply the latest guidance and novel systematic approaches to evaluate and present read-across strategies. View Brochure
  • Occupational Exposure Limits for Pharmaceuticals – published OELs are not available for most pharmaceuticals.  To ensure that workers in the pharmaceutical industry are adequately protected we have develop systematic approaches for hazard banding as well as provisional and final OEL development for a variety of sponsors. 

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  • 1250 Ohio Pike, Suite 197, Cincinnati Ohio 45102
  • 513.488.1990
  • TERA@TERA.ORG

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WEEL OEL

Occupational Exposure Limits (OELs) are designed to safeguard the health of healthy workers during their careers. These limits are based on the assumption of repeated daily exposure throughout a working lifetime, typically averaged over an 8-hour workday. Their purpose is to prevent both immediate (acute) and long-term (chronic) health issues arising from workplace exposures. It’s important to note that OELs are not intended for the general public, which includes vulnerable groups like infants, the elderly, and those with pre-existing health conditions.

Workplace Environmental Exposure Levels (WEELs) are health-based guidelines for chemical hazards in the workplace. These values represent air concentrations believed to protect the majority of workers from negative health effects resulting from occupational chemical exposure.

The WEEL Process
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The development of new or revision of existing WEELs is typically assigned to voluntarily designated subcommittees. A subcommittee usually comprises 3 – 4 members from the WEEL Committee. New WEELs are developed using the OARS-WEEL administrative standard operating procedure (SOP), while existing WEELs are usually revised every 10 years, unless the availability of significant new data which may impact the existing WEEL value compels the committee to make a revision sooner. The OARS-WEEL SOP contains procedures and guidelines governing conflicts of interest, draft document preparation, literature searches, draft document review, balloting process, post-ballot WEEL documentation quality assurance scientific review, and publication.

Once a subcommittee has prepared a draft WEEL document, a review of the draft is scheduled for the next available Committee meeting. The WEEL Committee members are expected to have reviewed all such drafts prior to the meeting. If no major changes are necessary to a draft, the attending Committee membership may, by a simple majority, approve the WEEL for balloting. Alternatively, the Committee may direct the subcommittee to revise the WEEL and present it for further discussion at a future meeting. If a ballot is not approved by a two-thirds majority of non-abstaining Committee members, it is discussed at the next Committee meeting to determine the appropriate course of action. Once the WEEL is approved by a two-thirds majority of non-abstaining Committee members, copies of ballot comments are forwarded to the designated subcommittee and all substantive comments must be addressed in the final draft. If resolution of a substantive comment results in a change to the WEEL value or a change in the basis for the value, the draft must be re-balloted.

Once all comments have been addressed on a successfully balloted draft, document formatting and editorial review are performed by TERA, before the draft WEEL document is made available for public comment (usually for a period of 30 days but may be extended if the need arises). After the public comment period has elapsed, comments are addressed by the subcommittee responsible for that specific draft, after which the WEEL documentation is submitted to Toxicology and Industrial Health (TIH), a peer-reviewed medical journal that covers research in the fields of occupational health and toxicology, for publication. A thorough review of the galley proof by the scientific content quality coordinator at TERA, and proofreaders and editors at TIH is the penultimate step before eventual publication of the WEEL documentation.

The WEEL Committee

The OARS-WEEL Committee is composed of volunteer experts specializing in the scientific determination of occupational exposure levels. This committee actively seeks a balanced representation of professionals from toxicology and industrial hygiene, drawing upon a diverse range of experience from industry, government, academia, and consulting. Importantly, each member contributes to the Committee based on their individual expertise and not as an official representative of their respective employer, organization, or agency.