A recent blog post by labor lawyer Steven Wodka highlights a concerning change in how the Occupational Safety and Health Administration (OSHA) requires chemical companies to classify cancer-causing chemicals that is likely to pose significant problems for OSHA’s ability to enforce how employers warn workers of the dangers associated with the chemicals they work with.

In OSHA’s 2012 revision to the 1994 Hazard Communication (HazCom) rule, the previous requirement that chemical companies consider chemicals that have been categorized as proven or potential carcinogens by either the National Toxicology Program(NTP) or the International Agency for Research on Cancer, or regulated as a carcinogen on an OSHA list of toxic and hazardous chemicals, has been replaced by an approach consistent with the United Nations Globally Harmonized System of Classification and Labelling of Chemicals(GHS).

OSHA’s rationale for adopting the GHS approach is that it will “improve the quality and consistency of hazard information” and in addition “help reduce trade barriers and result in productivity improvements for American businesses that regularly handle, store, and use hazardous chemicals while providing cost savings for American businesses.”

To appreciate the significance for worker health protection from this change, you need to know that the NTP program, which is part of the National Institute of Environmental Health Sciences, uses an extensive scientific review process involving input from a panel of scientific experts, several public comment opportunities, as well as reviews by other federal agencies and by two separate panels of experts.

The NTP's most recent Report on Carcinogens lists 240 chemicals as proven or “reasonably anticipated to be” human carcinogens.

The IARC process is also scientifically rigorous, involving interdisciplinary working groups of international expert scientists that review the published studies and evaluate the weight of the evidence that an “agent” (chemical or substance) can increase the risk of cancer.

 IARC lists 179 agents that are known or probable human carcinogens, and another 285 agents as possible carcinogens.

OSHA regulates 13 chemicals from its list of toxic chemicals as carcinogens.

Under the 1994 Hazard Communication rule, any of the chemicals on these lists were automatically considered cancer-causing and required to be labeled as such by the chemical companies that produced them. This simplified OSHA’s compliance assessment process – if the chemical was on any of these agency lists and appropriate warning labels were not provided, the company was cited for a violation of the regulation.

The 2012 revision to the rule tosses out this approach in the name of adopting the “globally harmonized” classification approach which allows the chemical companies to dispute whether a chemical already listed by the NTP or IARC should be classified, and therefore labeled, as causing cancer based on the company’s own assessment of the weight of evidence from scientific studies.

The chemical acrylonitrile, used in the manufacture of rubber, plastics, and fibers, provides just one example of where the chemical industry disputes the cancer classification. The National Occupational Exposure Survey (conducted from 1981 to 1983) estimated that 51,153 workers, including 25,320 women, potentially were exposed to acrylonitrile. The NTPand IARC list acrylonitrile as probable or possible human carcinogens, respectively. While results from human epidemiological studies are mixed, there is clear evidence from animal studies that exposure to acrylonitrile results in cancerous tumors.

In extensive comments to the U.S. Environmental Protection Agency (EPA), which is currently in the process of determining the health risks of acrylonitrile as part of its Integrated Risk Information System (IRIS) program, the industry’s Acrylonitrile Group concludes that “acrylonitrile is not likely to cause cancer at likely exposure levels”. Under the revised HazCom rule, acrylonitrile manufacturers would still be required to note that the chemical has been classified as carcinogenic by the NTP and IARC in material data safety sheets but could omit labeling the chemical as such. If cited by OSHA for this violation of the revised rule, the industry could dispute the NTP and IARC classifications, indicating that its own “weight of evidence” assessment indicated that such labeling was not appropriate.

To counter the massive resources that the chemical industry can bring to bear, OSHA would then need to devote its already limited resources to conducting its own assessment of the industry’s findings in response.

In comments following OSHA’s hearings on the 2010 proposal to revise the HazCom rule, the United Steelworkers Union stated that “the final standard should also state that if a chemical has been determined to be carcinogenic by IARC, the NTP, EPA or NIOSH – all of which are governmental or intergovernmental organizations – OSHA will require it to be labeled as such” and warned that the revised classification approach “would potentially replace the clear and protective rule for determining whether a chemical is harmful, with a much more vague approach that could result in removing hazard warnings for hundreds of toxic chemicals.”

Even if the scope of this dire prediction doesn’t come to pass, it will be essential for OSHA to protect workers by setting a high bar in future compliance directives for accepting industry claims regarding any challenges to IARC or NTP chemical assessments.