Annotated PELs from OSHA

OSHA has long recognized that its permissible exposure limits (PELs) for gases and vapors are in need of an update. Many of them have not been updated since the PELs were first made over forty years ago. As this blog has commented previously, OSHA faces an enormous administrative burden to produce updated or new standards.

OSHA has just published annotated standards in which the OSHA PELs are placed side by side with the NIOSH Recommended exposure limit (REL) and the ACGIH threshold limit values (TLVs). As discussed previously, the OSHA PEL is a legal maximum exposure limit, whereas the NIOSH REL and the ACGIH are values set based on the best available science but are considered recommendations as opposed to legal limits. (Note in some jurisdictions outside the US, the ACGIH TLVs are legally enforceable, not in their own right, but because the legislature in that country/province/territory etc. has adopted them into their law).

In OSHA’s own words:

OSHA also created another new web resource: the Annotated Permissible Exposure Limits, or annotated PEL tables, which will enable employers to voluntarily adopt newer, more protective workplace exposure limits. OSHA’s PELs set mandatory limits on the amount or concentration of a substance in the air to protect workers against the health effects of certain hazardous chemicals; and OSHA will continue to enforce those mandatory PELs. Since OSHA’s adoption of the majority of its PELs more than 40 years ago, new scientific data, industrial experience and developments in technology clearly indicate that in many instances these mandatory limits are not sufficiently protective of workers’ health. 

“There is no question that many of OSHA’s chemical standards are not adequately protective,” Michaels [David Michaels, Assistant Secretary for Labor, Occupational Safety and Health] said. “I advise employers, who want to ensure that their workplaces are safe, to utilize the occupational exposure limits on these annotated tables, since simply complying with OSHA’s antiquated PELs will not guarantee that workers will be safe.”
The annotated PEL tables provide a side-by-side comparison of OSHA PELs for general industry to the California Division of Occupational Safety and Health PELs, National Institute for Occupational Safety and Health recommended exposure limits, and American Conference of Governmental Industrial Hygienist threshold limit values. They offer an easily accessible reference source for up-to-date workplace exposure limits, which are available at
Under the Occupational Safety and Health Act of 1970, employers are responsible for providing safe and healthful workplaces for their employees. OSHA’s role is to ensure these conditions for America’s working men and women by setting and enforcing standards, and providing training, education and assistance. For more information, visit

The annotated PELs are available for not only gases and vapors but also solids. The annotated PELs are drafted around the PELs published in 29 CFR 1910.1000 and its tables Z-1, Z-2 and Z-3. The Annotated PELs are available at Z-1, Z-2 and Z-3.

The NIOSH RELs and ACGIH TLVs have been in use for many years and are widely respected. However many organizations have not understood the difference between them and the PELs and have relied solely on the OSHA PELs, as the prime means to protect their people, because of the legal status of the latter. These annotated PELs will hopefully encourage employers to use the RELs and TLVs with OSHA’s blessing and so create a safer work environment.