Recommended exposure limit

A recommended exposure limit (REL) is an occupational exposure limit that has been recommended by the United States National Institute for Occupational Safety and Health. The REL is a level that NIOSH believes would be protective of worker safety and health over a working lifetime if used in combination with engineering and work practice controls, exposure and medical monitoring, posting and labeling of hazards, worker training and personal protective equipment. To formulate these recommendations, NIOSH evaluates all known and available medical, biological, engineering, chemical, trade, and other information. Although not legally enforceable limits, RELS are transmitted to the Occupational Safety and Health Administration (OSHA) or the Mine Safety and Health Administration (MSHA) of the U.S. Department of Labor for use in promulgating legal standards.
All RELs are located in the "NIOSH Pocket Guide to Chemical Hazards", along with other key data for 677 chemical or substance groupings. The "Pocket Guide" is a source of general industrial hygiene information for workers, employers, and occupational health professionals.
NIOSH recommendations are also published in a variety of documents, including:
In addition to these publications, NIOSH periodically presents testimony before various Congressional committees and at OSHA and MSHA rulemaking hearings.