Occupational Exposure Limits – State of the Science

Posted on by Thomas J. Lentz, Ph.D.; Scott Dotson, Ph.D. and Deborah Hornback, MS


The process of developing and using occupational exposure limits is a cornerstone of industrial hygiene practice, with a history dating back to the 1880s. Occupational exposure limits, known as OELs, have not—until recently—evolved enough to reflect the advances in related sciences of toxicology, risk assessment, and exposure assessment. Much of the pioneering effort to develop and promote OELs as a risk management strategy occurred in the 1940s, when an organization now known as the American Conference of Governmental Industrial Hygienists (ACGIH) created a list of occupational exposure limits for 132 specific chemicals. While these limits represented a significant step forward in the practice of occupational hygiene, they lacked consistent guidelines, explicit definitions, and technical documentation. Gradually, these OELs and others have evolved to consider toxicological mechanisms of action, and uncertainties associated with the data available for assessing specific chemical hazards. Yet, there has still not been a concerted effort to explore how advances in toxicology, risk assessment, and exposure and risk management might better inform consistent and transparent processes for assessing chemical hazards and establishing OELs. To begin to tackle these issues, researchers at the National Institute for Occupational Safety and Health (NIOSH) worked with outside subject matter experts. They developed a collection of 10 articles published in the Journal of Occupational and Environmental Hygiene [JOEH, December 2015] focusing on the underlying principles for developing and interpreting OELs. The articles also discuss using and interpreting OELs in the context of evolving occupational risk assessment and management practices.

The first article, “State-of-the-Science: The Evolution of Occupational Exposure Limit Derivation and Application,” gives a background on OELs, including how they evolved and how they can be used to assess risk and manage workplace hazards. Other articles explore possibilities for incorporating advances in risk assessment, toxicology, and occupational hygiene into the process to develop OELs. The articles described below are listed in the order they appear in the journal.

In the preface to the JOEH collection of articles comprising the “State of the Science of Occupational Exposure Limit Methods and Guidance,” the guest editors state the following:


“…the 10 articles in this supplement of the Journal of Occupational and Environmental Hygiene provide a window into the future of OEL development. A combined effort by scientists at the National Institute for Occupational Safety and Health (NIOSH), Toxicology Excellence for Risk Assessment (TERA) and others, they present a systematic approach that begins with an understanding of systems biology, mechanisms of action and the early (i.e., “pre-clinical”) effects of toxic exposures including genetic and epigenetic phenomena. They incorporate novel approaches to exposure assessment and inhalation dosimetry, contemporary methods in risk assessment, statistics and decision logic, and considerations of the need to harmonize standards across the world…Many of these articles describe new technologies and data analytic methods that may be useful in overcoming data issues. The use of better models that address both uncertainty and variability in biological systems and exposure assessment offers particular promise.”

This collection contributes much to the underlying research into establishing OELs. The broad and varied topics addressed by the 10 articles blend modern concepts and advances in toxicology, occupational hygiene, risk assessment, and risk management. The articles offer extensive information and a treatment of the subject that may influence the science of setting OELs. The articles explore the continued relevance of occupational exposure limits, given evolving knowledge and guidance. They give insight into the ways OELs are formed and applied, and how effective they are and can be.

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Thomas J. Lentz, Ph.D., is Chief of the Document Development Branch in the NIOSH Education and Information Division.

 Scott Dotson, Ph.D., is a Lead Health Scientist in the NIOSH Education and Information Division.

Deborah Hornback, MS, is a health communications specialist in the NIOSH Education and Information Division.

Posted on by Thomas J. Lentz, Ph.D.; Scott Dotson, Ph.D. and Deborah Hornback, MS

6 comments on “Occupational Exposure Limits – State of the Science”

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    The interplay between occupational health and the need to balance that with state and federal employee rights and safety protections is another perspective that must be considered.

    Iam Jacy Kamal QA representative in Rhein Mina Pharm Biogenentics / Egypt

    Ian Asking if you could guide me to find OEL bank for biotechnology products

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Page last reviewed: February 22, 2016
Page last updated: February 22, 2016