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REGULATORY TOXICOLOGY AND PHARMACOLOGY 15, 73-82 (1992) Workshop on the Health Effects of HCI in Ambient Air Michael A. Kamrin Institutefor Environmental Toxicology. C-231 Holden Hall. Michigan State University. East Lansing. Michigan 48824 Received April 3. 1991 This article presents a summary of the proceedings of the Workshop on the Health Effects of HQ in Ambient Air, held in Detroit, Michigan, on October IS, 1990. Participants addressed three topic areas: sources, levels, and chemistry of HQ in ambient air; toxicity of atmospheric HQ to humans and animals; and the need for future research on toxicity and exposure. Consensus conclusions related to each of these topic areas, arising form the deliberations of the workshop participants, are presented. These include: (I) atmospheric HQ will most commonly exist in the gaseous form; (2) long-range transport of HQ is probably oflimited importance; (3) ambient HQ levels are in the low parts per billion range; (4) irritation of the upper airways appears to be the most sensitive indicator of exposure; (5) such effects are likely to occur only at exposure levels much greater than those measured in ambient air; and (6) future health research should focus on occupationally exposed populations and potentially sensitive subgroups, e.g.t asthmatics, o 1992 Academic Press, lac INTRODUCTION The objectives of the Workshop on the Health Effects of HCI in Ambient Air were to evaluate (1) available information about sources, levels, and chemistry ofhydrogen chloride in ambient air; (2) current knowledge about the toxicity of atmospheric hy drogen chloride to humans and animals; and (3) the need for future research on the toxicity of and exposure to hydrogen chloride in ambient air. To accomplish this, a group of 32 scientists representing a variety of disciplines and sectors met for a full day of intensive work on October 15, 1990, in Detroit, Michigan. The Workshop was coordinated by the Institute for Environmental Toxicology, Michigan State University. In preparation for the meeting, participants were provided with a number of ma terials. Included were six articles describing experiments on the health effects of HCI (Mglek and Alarie, 1989; Burleigh-FIaycr el ai, 1985; Hartzell ct at., 1988; Kaplan el at.. 1988; Albert et ai, 1982; Scllakumar el al.. 1985); a summary of the National Research Council (1987) evaluation of HCI; and two review articles on the health effects of acid aerosols (Spcnglcr el ai. 1990; Soskolnc ct ai. 1989a). One additional article describing a risk assessment of sulfuric acid (H>S04) was distributed at the lime olThe meeting (Rao and Brown, 1989). 7.1 BFG15509 027.1-2100/92 S1.00 Ci'I'vki'.IiI *5 (iv Ati.l.'iim1 tV-iv Iv All <<r.l<U u( Ii'|ii<l<ium < ,il> I,him nvnill too62.55*2 74 MICHAEL A. KAMRIN The Workshop began with three presentations to delineate the important health and environmental issues. Participants then were divided into smaller groups to fa cilitate discussion of the major questions. These breakout sessions were structured to identify areas of consensus and those requiring further study. All participants then met as a group to hear summaries ofthe breakout sessions and discuss the conclusions that were reached. The implications of the group conclusions for assessing human risk were also addressed during this final segment of the meeting. This report contains summaries of each of the formal presentations followed by discussions of the issues raised in the respective presentations. The discussion sections summarize the views of the participants as expressed in both the breakout and the plenary sessions. In addition, the report reflects comments provided by participants subsequent to the Workshop in response to a draft version of this manuscript. While it was not possible to incorporate all comments ofall individuals, this meeting summary reflects the consensus of the participants. t 1 HQ IN AMBIENT AIR Sources and Levels The first speaker, Gerald Keeler (University ofMichigan) discussed sources ofHCl, the nature of HQ emissions and their atmospheric distribution and fate, and concen trations of HQ in ambient air. The two major sources of atmospheric HCI are fossil fuel burning and incineration ofdomestic and industrial waste (Sturges and Harrison, 1989; Lightowlers and Cape, 1988). The fossil fuel of most concern is coal. The amount of HCl generated from burning of coal depends on its chloride content which varies from 0.0029 to 0.095% (Gladney et al., 1984; Olmez, 1990). The chloride content of fuel oils.is generally low, as is the concentration in'gasoline, where chloride is used as a scavenger for lead (Lightowlers and Cape, 1988; Pierson and Brachazek, 1983). The major contributors to the chlorine content in municipal solid wastes are polyvinyl chloride and papec (lightowlers and Cape, 1988; Michigan DNR, 1986). The relative contributions ofincineration and coal burning can be estimated using information from existing facilities. A high-capacity resource recovery facility, operating 24 hr a day, 5 days a week, and burning 650,000 tons of solid waste (containing 6.5 lb HCl/ton) per year is estimated to emit uncontrolled emissions of about 2000 tons of HCl/year (Michigan DNR, 1986; Brunner, 1985). A high-capacity coal-fired power plant, burning 2,000,000 tons/year of bituminous coal (with an HCl content of 0.0925%), emits an estimated 1700 tons of HCl/year. Thus, these two types of sources appear to emit roughlyequivalent amounts of HCl into the air. However, the source type that is the largest contributor to HCl in a particular geographical region depends on the amount and type of fuel consumed and the control equipment utilized on each facility. In addition jo the combustion of coal and solid waste, there are a number of other sources that contribute to HCl in ambient air. These include glass manufacturing, irou-slccl manufacturing, the ceramic industry, cement production, the chemical in dustry, rocket firing, and natural sources, e g., volcanoes and sea salt (National Research Council. 1976; I'enton e( ai. 1980; Clegg and llrimblecombc. 1985). In most areas, these secondary sou ices contribute 10% or less to (lie total 1 K.l emissions (I .ighiowlers BFG15510 2X579002 $