Preventing Cancer: NIOSH Eliminates Recommended Exposure Limits for Carcinogens

According to the American Cancer Society, about 40 percent of Americans will develop cancer during their lifetime, and about 20 percent will die of cancer. An unknown percentage of these cancers are caused by workplace exposure to carcinogens. To aid in the prevention of occupational cancer, the National Institute for Occupational Safety and Health (NIOSH) develops guidance to protect workers from occupational exposure to carcinogens.

NIOSH issues a policy document, its Chemical Carcinogen Policy, that governs how NIOSH classifies chemicals as occupational carcinogens, sets risk management limits for workers exposed to carcinogens, and incorporates information on the analytical limit of quantification (LOQ). In December 2016, NIOSH updated its Chemical Carcinogen Policy for the first time since 1995—and the agency has made some significant changes.

Identifying Occupational Carcinogens

Not all occupational chemicals are carcinogens—and not all carcinogens are a problem in the workplace. Under its updated policy, NIOSH will evaluate potential occupational carcinogens using existing cancer hazard assessments completed by the U.S. National Toxicology Program (NTP), the U.S. Environmental Protection Agency (EPA), and the International Agency for Research on Cancer (IARC), whenever possible. Based on those documents, NIOSH will assess a substance’s risk and its occupational relevance, and recommend ways of reducing the risks of chemicals that it designates as “occupational carcinogens.”

No More RELs for Carcinogens

To assist employers in protecting workers from the hazards of occupational exposure, NIOSH establishes recommended exposure limits (RELs) for individual substances. The REL is not a regulatory limit, although RELs are structured similarly to OSHA’s permissible exposure limits (PELs), and are sometimes used by OSHA in establishing PELs.

In its new Chemical Carcinogen Policy, NIOSH states that it will no longer establish RELs for carcinogens. An REL is established based on the assumption that there is a “safe” level of exposure to a given substance, but there is no known safe level of exposure to occupational carcinogens. Instead of an REL, NIOSH recommends that employers reduce exposure to occupational carcinogens first by elimination or substitution and by the implementation of engineering controls, if practical, and recommend the use of administrative controls before use of personal protective equipment (PPE).

For situations in which the exposure cannot be eliminated, NIOSH will:

  • Calculate a range of risk estimates, from 1 excess cancer case in 100 workers to 1 excess cancer case in 1 million workers over a 45-year working lifetime when the data permit; and
  • Set a risk management limit for carcinogens (RML-CA). An RML-CA is the daily maximum 8-hour time-weighted average concentration of a carcinogen above which a worker should not be exposed. NIOSH will set the RML-CA for an occupational carcinogen at the concentration corresponding to the 95% lower confidence limit of the 1 in 10,000 (10–4) risk estimate when analytically possible.

When it has enough data to do so, NIOSH will complete a quantitative risk assessment (QRA) and use the results of the QRA to perform both tasks.

Addressing Feasibility

Sometimes, the technology does not exist to measure an occupational carcinogen at the 1 in 10,000 risk estimate level. In those cases, NIOSH will set the RML-CA at the limit of quantification (LOQ) of the analytical method for that occupational carcinogen. In addition, NIOSH will continually evaluate available engineering controls and make that information available for employers when publishing RML-CAs so that employers can reduce exposures as much as is technologically feasible.