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Threshold limit value

Hazardous substance exposure threshold

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  • 6 chapters

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The TLV is an estimate based on the known toxicity in humans or animals of a given chemical substance, and the reliability and accuracy of the latest sampling and analytical methods. TLVs do not take into account financial or technical feasibility for application in the workplace, instead solely focusing on health based recommendations to prevent adverse health effects. It is also not a static value, since new research can often modify the risk assessment of substances, and new laboratory or instrumental analysis methods can improve analytical detection limits.

The TLV is a recommendation by ACGIH, with only a guideline status. As such, it should not be confused with exposure limits having a regulatory status, like those published and enforced by the Occupational Safety and Health Administration(OSHA). However, many OSHA exposure limits are not considered by the industrial hygiene community to be sufficiently protective levels since the toxicological basis for most limits have not been updated since the 1960s. OSHA acknowledges this and recommends supplementing regulatory standards with alternative updated and stricter standards, "even when the exposure levels are in compliance with the relevant PELs", while specifically mentioning the TLV as one such standard.

History

Many people accredit the idea of government responsibility for the protection of its workers in the workplace to Franklin D. Roosevelt in the Great Depression era. The formation of the National Conference of Governmental Industrial Hygienists (later to be renamed the American Conference of Governmental Industrial Hygienists) in 1938 was a direct response to this idea.

Although the first meeting of the ACGIH was held in 1938, the first exposure limits of the group were not published until 1946, then referred to as Maximum Allowable Concentrations. These standards were split into 4 categories: Gasses and Vapors, Toxic Dusts, Fumes, and Mists, Mineral Dusts, and Radiations.

In 1970, the US Occupational Health and Safety Act was signed into law, which created the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health. Shortly after this law passed, OSHA implemented its first Permissible Exposure Limits, which were adopted directly from the 1968 ACGIH TLVs.

In 2008, the Sustainable TLV/BEI fund was created to allow for the continued financial support of the development of TLVs and BEIs. This fund provides "additional opportunities for raising funds to support and sustain the core mission and value of developing and promoting occupational exposure guidelines." This fund ensures that TLVs and BEIs will continue to have the necessary financial support to be created and revised in order to provide up-to-date standards.

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