Emergency exposure limits: a guide to quality assurance and safety.

Emergency exposure limits (EELs) are necessary in disaster prevention, preparation, and repression. Occupational EELs are available for many chemicals, but are of low toxicological adequacy. An animal experimental EEL of high toxicological adequacy available for many irritant chemicals is the concentration causing a 50% decrease in respiratory rate (RD50). The most outstanding EELs for the general population are the emergency response planning guidelines (ERPGs). A theoretical framework for a three-limit system is developed by the European Chemical Industry Ecology and Toxicology Center (ECETOC). ECETOC found over one order of magnitude variation between assessments of several companies. Nine selected EELs were classified in three clusters of increasing degrees of seriousness of health effects. There was little consistency within clusters, making it impossible to combine EELs. It is recommended to develop a toxicologically adequate EEL in an intercontinental context with cooperation of industry and (supra)national regulatory bodies. ERPGs can be taken as a start. The framework developed by ECETOC can be used to improve the limit setting procedure. A 5- to 10-year update should become part of the procedure. Attention should be devoted to the use of expert judgment. The minimal uncertainty in EELs should be expressed by presenting ranges instead of single values.