In the Federal Register for August 23, 2011, the National Institute of Occupational Safety and Health (NIOSH, one of the Centers for Disease Control and Prevention) announced a 30-day public review period for its carcinogen and "recommended exposure limit" (REL) policies[1].  This public comment period is an excellent opportunity to assist NIOSH in establishing a more modern and flexible approach to categorizing carcinogens that reflects current scientific and risk management practices.

By way of background, 29 CFR Section 20(a)(3) of the Occupational Health and Safety Act of 1970 charges NIOSH to “describe exposure levels that are safe for various periods of employment, including but not limited to the exposure levels at which no employee will suffer impaired health or functional capacities or diminished life expectancy as a result of his work experience."  While both NIOSH and the Occupational Safety & Health Administration (OSHA) set exposure limits for hazardous substances in the workplace (in this case, carcinogenic substances in the workplace), the RELs set by NIOSH are “recommended” and lack the legally enforceable status of the “Permitted Exposure Levels” (PELs) set by OSHA.

First published in 1976[2], the original NIOSH cancer guidelines were released two years prior to the OSHA Cancer Policy[3].  These guidelines called for “no detectable exposure levels for carcinogenic substances.”  When the OSHA Cancer Policy was adopted in 1980, NIOSH “generally agreed” with the OSHA-suggested definition of “potential occupational carcinogen”:

"[A]ny substance, or combination or mixture of substances, which causes an increased incidence of benign and/or malignant neoplasms, or a substantial decrease in the latency period between exposure and onset of neoplasms in humans or in one or more experimental mammalian species as the result of any oral, respiratory or dermal exposure, or any other exposure which results in the induction of tumors at a site other than the site of administration.  This definition also includes any substance which is metabolized into one or more potential occupational carcinogens by mammals."

This single category of carcinogens is now recognized by NIOSH as a “major limitation[4].”  According to the announcement, “[t]his policy does not allow for classification on the basis of the magnitude and sufficiency of the scientific evidence.  In contrast, other organizations, such as the International Agency for Research on Cancer (IARC) and the National Toxicology Program (NTP) allow for a more differential classification[5].”

In its August 23 announcement, NIOSH seeks comments on the following five questions:

  1. Should there explicitly be a carcinogen policy as opposed to a broader policy on toxicant identification and classification (e.g., carcinogens, reproductive hazards, neurotoxic agents)?
  2. What evidence should form the basis for determining that substances are carcinogens?  How should these criteria correspond to nomenclature and categorizations (e.g., known, reasonably anticipated, etc.)?
  3. Should 1 in 1000 working lifetime risk (for persons occupationally exposed) be the target level for a REL for carcinogens or should lower targets be considered?
  4. In establishing NIOSH RELs, how should the phrase “to the extent feasible” (defined in the 1995 NIOSH Recommended Exposure Limit Policy) be interpreted and applied?
  5. In the absence of data, what uncertainties or assumptions are appropriate for use in the development of RELs?  What is the utility of a standard “action level” (i.e., an exposure limit set below the REL typically used to trigger risk management actions) and how should it be set?  How should NIOSH address worker exposure to complex mixtures?

A revision in the REL for carcinogens could have significant regulatory implications for a broad range of industries.  Therefore, this public comment period is an important opportunity for industry and other interested parties to advocate for an approach to categorizing carcinogens that reflects current scientific and risk management practices.

Some of the important issues that will need to be considered include whether NIOSH should adopt the IARC or NTP approach to categorizing carcinogens, as well as the potential revisiting of the working lifetime target risk.

Comments will be accepted through September 22, 2011, at NIOSH Docket 240. Click here to access the NIOSH Docket.  A public meeting will be scheduled around November 2011 for stakeholders to ask questions and provide additional feedback.