Occupational Exposure Limits (OELs) are limits established for occupational exposure to specific substances. These limits are determined by organizations tasked with safeguarding worker health, using a combination of toxicological and epidemiological data, and representing the maximum concentrations to which it is believed that most workers may be exposed in an occupational setting on a regular basis without experiencing negative health effects. At present, the vast majority of Occupational Exposure Limits are associated with airborne concentrations of chemical agents to which employees might be exposed through the inhalation pathway. Some physical agents (e.g., noise, heat, cold, radiation, etc.) have also been assigned OELs; however, these are few.
Several organizations routinely establish and update OELs. One of these is the Occupational Safety and Health Administration (OSHA), which operates as part of the United States Department of Labor (DOL). OSHA’s Occupational Exposure Limits are called Permissible Exposure Limits (PELs). In the U.S. and its territories, these are enforceable legal standards. Employers must maintain employee exposures below these limits or be subject to regulatory action, including fines.
Most of the OSHA PELs are found in Tables Z-1, Z-2, and Z-3 of 29 CFR 1910.1000, which were established as part of the Occupational Safety and Health Act of 1970. Unfortunately, most of these PELs have not been updated since that time. The difficulty in this lies in OSHA’s burden to demonstrate both a scientific and financial rationale for lowering its PELs. As a result, most of the changes that have taken place have come through specific rulemaking efforts that have established detailed regulations for individual chemical substances (e.g., benzene, methylene chloride, crystalline silica, etc.). At the present time, there are over three dozen of these “regulated” substances in the general industry, construction, and maritime standards. The program elements contained in these standards include detailed requirements for industrial hygiene, medical surveillance, sampling methods & laboratory analysis, engineering controls, personal protective equipment (PPE), training, and recordkeeping.
Other major organizations that establish Occupational Exposure Limits include ACGIH, AIHA and NIOSH. These entities are further explained in the table below. In addition, informal Occupational Exposure Limits may be developed by manufacturers, who possess a more in-depth knowledge of the potential hazards associated with exposure. Finally, OELs may be established by trade organizations and by other countries. While not necessarily binding on US employers, these OELs may be used to form a more complete understanding of a substance or be used voluntarily in the event that no US OELs have been published.