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Hazardous air pollution control Increase community awareness
In lune 1985, EPA announced its twopart stratesy for dealiig with hazardous air pollutants. The fist portion would regulate, under Section 112 of the Clean Air Act, toxic chemicals that are emitted through routine releases at various facilities across the country. The second major portion deals with acutely hazardous chemicals that result from sudden, nonroutine releases. In the Dec. 17, 1985, Fedeml Register (Vol. 50, No. 242, p. 51451) EPAannounced the availability of two “interim” documents that address these nonroutine releases and solicited public comment on them. The public comment period closes March 17. The first of the two documents is a 165-page text that explains how communities can identify acutely toxic chemicals, where their release into the air may cause harm, how to deal with releases, suggestions for preparing emergency response plans, and a list of some 400 chemicals that meet EPA’s criteria for acute hazards. The second is a much larger compendium of profiles of the acutely hazardous air pollutants. The profiles summarize information that EPA has gathered from previously compiled publicly available sources, primarily the Registry of Toxic Effects of Chemical Substances (RTECS) data base of the Occupational Safety and Health Administration. The profiles describe chemical and physical characteristics, health effects, potential reactivity, and mious methods for handling for each :hemical.
In the introduction to the documents, EPA Administrator Lee Thomas states that the purpose is to increase community awareness of chemical hazards and to assist with the development of state and local emergency response plans. The guidelines will help communities to identify leaders and work groups to study local preparedness, identify methods that wnununities can use to analyze sitespecific hazardous pollutants, and suggest ways to prepare emergency response plans to deal with sudden releases of toxic chemicals. EPA emphaslzes that the intenm documents differ significantly from the guidelines prepared under Section 112. The latter are keyed to an assessment of the long-term chronic toxicity of exposure to a hazardous chemical; the new guidelines do not directly incorporate exposure to specific chemicals. EPA spokesmen also acknowledge that merely listing a chemical does not in itself demonstratea potential for serious human health effects. Rather, listing simply “indicates a need for the wmmunity to undertake a program to investigate and evaluate the potential for accidental exposllres.” Assessment of any actual risk following accidental releases is based on an analysis of the chemical’s toxicity coupled with an evaluation of exposure. There can be little doubt, however, that the presence of any chemical on this list will raise the concern that any amount may be dangerous in and of itself. Therefore, it is important to look at the profiles and at the cntena on which the aeencv has based its judgment of hazard. Y
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Tests for acute hazards EPA has identified three t termine whether a chemical falls into the acutely hazardous category: dermal application, oral ingestion, and inhalation. In each case, EPA has used as its prime criterion the dose or concentration that will kill one-half of a group of
test animals-the lethal dosekoncentration 50 (LD50,LC50). For dermal applications, the cut-off value is 50 ppm, for oral doses it is 25 ppm, and for inhalation the concentration is 0.5 mglL for up to 8 h. Any chemical for which a dose causes 50% lethality at a lesser level is included on the acutely hazardous list. Clearly, public wmment is needed on the issue of relationships between dermal, oral, and inhalation exposures in determining whether a hazardous air pollutant should be included on the acutely toxic list. A second issue is the sufficiency of information in cases where experimental data do not identify the coucentration level for 50% lethality. Here EPA has used an L h 0 value, that is, the lowest doselconcentration at which some animals die. An LDLo value may be much smaller than an LDso level, because it is only necessary to observe some animal deaths to justify a listing. As a result, the 400 chemicals on EPA’s acutely hazardous list vary greatly in toxicity. They range from many pesticides in routine use, to chemicals typically considered acutely harmful (chlorine, fluorine, phosgene, nitric oxide, strychnine, and sulfur trioxide), to chemicals much less frequently perceived as acutely hazardous, such as cobalt and nickel. (For example, the cobalt profile notes that “Ccbalt is considered a slightly toxic agent which causes readily reversible changes at the end of exposure.”) Complete toxicological profiles are not uniformly available for all chemicals, and EPA has used data that were quickly and publicly accessible. Therefore the profdes should be reviewed from the standpoint of adequacy and usefulness in judging effects from the three exposure routes.
Richard M. Dowd, Ph.D., is a Washington, D. C., consulrant to Environmental Research & Technology, Inc.
