Tales of acute risk assessment: health effects made out of whole cloth.

BACKGROUND: Risk assessment utilizes human and animal studies and mathematical models to arrive at threshold exposures for toxic effects of various chemicals. In 1995 the Environmental Protection Agency (EPA) formed an acute risk assessment committee to assist in the planning for worst case chemical releases. The National Advisory Committee for Acute Exposure Guideline Levels (AEGL) examines the toxicological properties and studies of each chemical and then recommends appropriate levels. For the majority of chemicals, the committee relies on animal data (where the most data exists) supplemented with a limited number of human studies. In some cases, human studies are relied on to derive AEGL values.

METHODS: In the published levels for hydrogen cyanide (HCN), the AEGL committee used five human studies and a "weight-of-the-evidence" approach. A number of these studies did not investigate adverse health effects, however, the AEGL committee used these studies as evidence that no health effect occurred. In addition, a number of other errors in conflict with well accepted principles of industrial hygiene were made.

CONCLUSION: In order to adequately evaluate human studies, risk assessment committees must be composed of a balance of professionals with a wide variety of expertise, including epidemiology and industrial hygiene.