Various organizations and agencies have proposed inhalation levels of toxic chemicals that may be experienced with negligible health risks on a once-in-a-lifetime exposure basis. Many of the chemicals for which such exposure levels have been defined are present in any given area on a regular basis, which means there are chronic as well as acute exposures to consider. Others represent repeated exposures for emergency response personnel because of multiple release incidents from the same source, or multiple sources in the area. Additionally, special risks of high level acute exposures such as cancer initiators vs. cancer promoters may have been ignored. The inherent error and dangers are illustrated by specific cases of arsenic, benzene, mercury, and vinyl chloride. It is recommended that no "minimal risk" or "safe" exposure levels for emergency response personnel or the general public should ever be promulgated that are less protective than the most conservative short-term exposure limits for the workplace.
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