ACGIH and TLVs

The American Conference of Governmental Industrial Hygienists (ACGIH), established in 1938, has played a critical role in developing limits for occupational exposure.

The two major activities of the ACGIH are to: (1) determine safe or "acceptable exposure levels" for workplace chemicals by developing exposure standards and, (2) to promote the development of better methods to measure exposure levels.

The ACGIH has developed two types of occupational exposure limits: Threshold Limit Values (TLVs) and Biological Exposure Index.

Threshold Limit Values (TLVs) provided guidance on permissible concentrations of airborne contaminants and physical agents (such as heat, cold, noise, vibration, and electromagnetic radiation).

There are three types of TLVs:

TLV-TWA (Time Weighted Average)

The Average concentration for a normal 8 hour workday over a 40 hour work week that workers may be exposed to day after day.

For those substances that are absorbed as the result of skin, mucous, or eye exposure, a large body dose may result. In these cases, the TLVs are also provided with a "skin notation". This alerts to the need to protect workers from skin or mucous membrane absorption even if respiratory protection has been provided. Those substances for which there has been a determination of carcinogenicity are also identified with a confirmed (A1) or suspected (A2) carcinogen tag.

TLV-STEL (Short Term Exposure Limit)

A supplementary standard to the TLV-TWA consisting of a concentration that workers can be exposed to for no more than a short period (15 minutes). TLV-STELs protect from the acute effects of substances whose primary toxic effects have been reported from high, short term exposures of animals or humans.

TLV-C (Ceiling)

A concentration that should not be exceeded at any time. In some cases, the TLV-C may be the only TLV category.

(Moeller, Dade W. Environmental Health, 1992, p. 40)

(Moeller, Dade W. Environmental Health, 1992, p. 42)

Biological Exposure Index provides a limit for chemicals or their metabolites in biological specimens (urine, blood, exhaled air) collected from workers at specified intervals.

(Moeller, Dade W. Environmental Health, 1992, p. 41)