Acid aerosols: The next criteria air pollutant?
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I
Frederick W. Lipfert Samuel C. Morris Biomedical and Environmental AssessmenfDivision Brookhaven Nafional Labomfory Upton. NY 11973 Ronald E. Wyzga Elecrric Power Research Insfifme Palo Alfo, CA 94303
The acidity of certain air pollutants has long been a subject of concern, perhaps best expressed by the ongoing debate 1316 Envlron.Sci. Technol.. Voi. 23. NO.11, 1989
0013”)36Xf891W25131601.~~ 1989 American Chemical Society
on the effects of acidic precipitation. In recent years, this issue has broadened to include the direct health effects of breathing acidic pollutants, especially fine particles or aerosols. The main Constituents of these aerosols are sulfuric acid and various sulfate salts. In 1988, EPA‘s Clean Air Scientific Advisory Committee (CASAC) requested the agency to take steps toward listing acid aerosols as a criteria air pollutant, with specific reference to acidic particulates, by establishing a reference measurement method and assessing ambient concentration levels of acid aerosols. Human exposure levels then could be compared with data from the health effects literature to determine whether there is a need for regulation. One way to assist this regulatory decision is through a risk assessment that estimates potential health responses at current ambient levels. The National Academy of Sciences has defined a framework for such risk assessments (1). Considerable research is under way on the health effects of acid aerosols, including animal toxicology, human clinical studies, and a major epidemiological study that ultimately will involve 24 cities.
conclusions regarding the need for further research. In contrast with existing criteria pollutants, which are operationally defined by “reference” methods of measurement, acid aerosols have been defined in the literature according to classical definitions. The term “acid aerosol” refers to a gaseous suspension of either solid or liquid particles that yield hydrogen ions (Hi ). The gas in which the particles are suspended may or may not include acid gases. Although technically acid fogs are included in this definition, we have elected to exclude them because of their substantially larger particle sizes. Strong acids found in the atmosphere include HCI (gas), HNO, (gas), H2S04 (aerosol), and NH4HS04 (aerosol). Weak acids include dissolved SO2 (H,SO,); nitrous acid (HN02); formic, acetic, and pyruvic acids (mostly gas phase), and ammonium sulfate [(NI%)2S04]. Whether an atmospheric contaminant exists as a particle or as a gas is of interest primarily with regard to its rate of deposition to the receptor of interest. For example, large particles ( > 5 pn) and gases often deposit in the upper airways of the lungs. whereas smaller particles are capable of penetrating deep into the lung to alveoli. For convenience, aerosol acidity is often expressed in (mass) units of H2S04. Because H2S04and NH4HS04 are the strong acids present in the atmosphere most commonly as particles, discussions of acid aerosol issues often center on acidic sulfate particles. Most of these particles originate from SO2 emissions that are slowly oxidized to form H2S04, which may, in turn, be neutralized by ammonia to various degrees. The final neutralization step may take place in the respiratory airways as a result of contact with ammonia in the breath. The terms “exposure” and “dose” also require definition. In this paper, the exposure of a population to a pollutant is defined as the sum of the products of the concentrations of pollutants in the various micrwnvironments, encountered over some interval, times the elapsed time the exposed persons spend in each microenvironment. This is generally not the Same as the product of the EPA published a compendium ot XI- sampling time and the concentration reentific and technical information on corded by some fixed-location monitor. acid aerosols in 1988 (2), and the pro- The biologically relevant dose, which ceedings of a symposium on the topic is the mass of pollutant received by appeared this year (3).In this paper, we some target organ or tissue, depends will emphasize human exposures in not only on the exposure but also on the comparison with the experimental con- breathing rate, particle size, and any ditions used to establish health re- chemical reactions taking place within sponses and with the associated data the airways. The dose of concern for a base on health effects. We also will dis- particular type of biological response cuss a risk assessment framework for also may depend on the pattern of conacid aerosols. Finally, we will draw centrations versus time. ’
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Ambent concentrations The local ambient concentration of acidity depends on the balance between acids and bases and therefore is more difficult to estimate by means of meteorological dispersion models than are the current criteria pollutants. Upper limits could be estimated by ignoring the variability of neutralization by ammonia, but realistic exposure estimates should be based on direct measurements. Mammals, bacteria, soil, combustion processes, chemical plants, and sewage treatment facilities emit ammonia. It should not be surprising, therefore, to find that aerosol acidity is highly variable in both time and space, which makes characterization of population exposures more difficult. Methods of measuring acid aerosols. Methods for determining the acidity of particles vary from a simple ion balance to various technologically complex protocols; these have been reviewed in detail elsewhere (2, 4-6). Recent technological developments have emphasized the protection of samples from neutralization by ambient ammonia (7,8). Most methods involve the aqueous extraction of soluble particles collected on a filter and the determination of the concentrations of sulfate and other ions in the solution through standard methods such as ion chromatography, pH measurement, or titration. EPA’s “Acid Aerosols Issues Paper” (2) and the review article by . Lioy and Waldman (6) considered only direct measurements of H + or H2S04. Such measurements are required for the consideration of an air quality standard. H’ estimates may, however, be made by using ion charge balance (4). as often has been done with precipitation data. This method allows acidity estimates to be made using large data bases that include and NH4+ (reliable NO,- data also would be desirable), but it tends to overestimate acidity in urban locations (4, 9). The use of these large data bases (IO,11) can provide information on spatial and temporal trends not currently available elsewhere, provided that care is taken to account for sampling artifacts (4. 5). Ambient concentration levels. Although the literature on measurement of aerosol acidity is extensive, because much of the effort has been centered on specific research projects, there are only a few long-term data sets. Lioy and Waldman (6j, for example, give concentration ranges in their review but no long-term data. Lipfert (4) used the ion charge balance technique to estimate long-term (several months or more) or annual concentrations of a p parent acidity in Eastern U.S. urban and suburban areas, which were generally in the range @8 & n 3(as H2S04), Envlron. Scl.Technol., Val. 23. NO. 11, lgsg 1317
with the more urban sites indicating lower concentrations than nonurban or rural sites. Peak short-term acidity levels can be episodic. Levels will depend on sampling location, the averaging time used, and the number of samples obtained. For example, the EPA issues paper (2) reports 1-h equivalent H2S04 concentrations as high as 28 pg/m3; 611, 15 pg/m3; 12-h, 36 pglm’; 24-h, 14 pg/ m3; 36-h, 26 pg/m3; and 48-h, 11 pg/ m3. Lipfertk review (4) states that most sites had 24-h peak values in the range IC30 pglm’, with urban sites at the lower end of this range. The overall maximum was 58 pg/m3as H2S04for a 24-h sample in southern Ontario, based on ion charge balance. Data on ahnospheric acidity at very short averaging times (< 3 h) generally have been limited to flame photometric determinations of sulfuric acid. Most filter-based data reported in the l i t e r a m have used 24-h samples, with a few instances of 3-, 6-, or 12-h samples. In all cases, the values reported should be interpreted in the context of the speciEc sampling and analytical methods used. More recently, Spengler et al. (12) have reported the results of monitoring aerosol acidity in four U.S. cities for about 10 months and in rural Ontario for about six weeks. They used annular denuder technology and determined H from the pH of the filter extract (7). The highest spikes occurred in Ontario; Steubende, O H and Kingston, TN, at 28 (12-h average) and 17 and 14 (24-h averages) pg/m3, respectively, but as interpreted from the timeline plots, these events were of relatively short duration. Concentrations persisting a few days or more were at the 56 pg/m3 level. All of the long-term averages were less than 2 pg/m3 and appear to be controlled by the frequency of peaks. AU current measurements of aerosol composition and acidity are associated with research programs. Concentrations of acidic particles are being measured at a number of locations in conjunction with various health studies whose protocols generally use 24-h sampling with inlets that capture particles about 2.5 lun and smaller. Other aerosol measurement programs are associated with the National Acid h i p itation Assessment Program and involve rural sites. The California Air Resources Board has conducted an extensive air quality characterization study in the South Coast Air Basin, including acid gases and particles. issues in the characterization of population exposures to acid aerosols. EPA recently held a workshop (13) on acid aerosol measurement methods and concluded that the tech+
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Envlron.Scl.Technol., Vol.23, No. 11. 1989
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3 h data, July 1978 O-0
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nology had progressed sufficiently for a formal evaluation of methods, focusing There are, howon total acidity @I+). ever, a number of unresolved issues with respect to ambient measurements, particularly when these issues are viewed in the context of the available information on health effects (14). Species. Although current technology has evolved around measuring H+ , health effects information is concerned largely with H2S04, as discussed be low. There are no current monitoring programs specifically for H2S04. Less attention is given to measuring N&+ (which controls the degree of implied neutralization of H2S04), for which there may be either gains or losses on filters (5). Schwartz et al., however, r e port data for both Ht and H2S04 for a group of six cities; the median level of H2S04 was about 15% of the median level of H+ (15). Concenrraiion vs. time. Much of the current acid aerosol measurement technology focuses on 12- or 24-h sampling. The long-term averages of the data developed tend to be low, on the order of a few pg/m3 (4, 12, IS). The measurement technology has encountered problems with sampling artifacts and interferences which are most important at low H+ levels; for example, when the aerosol is mostly neutralized. Our analysis of existing data (Figure 1) shows that use of 24-h sampling periods may underestimate shorter term peaks hy as much as 50%; this 6nding has been confirmed by recent measure ments in Ontario (12). Figure 1 also shows that as averaging times are increased beyond 24 h, the maximum concentrations of H+ do not decrease rapidly. These trends also may be seen in the data of Lioy and Wald-
man (6) and imply that time (T) rather than concentration (C) will tend to dominate the exposure product C x T. Ambient sampling should be conducted for the shortest practicable averaging times on an everyday basis, and future health effects experiments could usefully emphasize longer exposure times at lower concentrations as well as repeated exposures. It also is important to characterize the joint exposure profiles of acid particles and other pollutants, including acid gases such as HN03, which may exhibit different temporal patterns. Seasonal variabilify. Many of the recent experimental campaigns have been conducted in the summer, when sulfate and ozone concentrations tend to be highest (4, 6, 16, 17). The seasonal trend in acidity will differ according to the averaging time considered; the highest short-term peaks have been seen in the summer, but longer term averages may peak during other seasons when biogenic ammonia is reduced (4). Composition of sulee aerosols. Our analysis (Figure 2) shows that the average molar h!&+/S042- ratio (about 75 % average neutralization in July and 50% in October) tends to remain constant over a large range in and site locations-other factors, such as season, remaining constant. This analysis implies that the ammonia supply generally is not the limiting factor at any of the sites, and thus raises questions about the dynamics of acid neutralization and the relative roles of local NH3 vs. transported N&+ . Panicle size. Information on composition or acidity by particle sue is liited. Results of experiments have shown the most acidic particles to be in
0 NewYohCity
a Whiteface Mountain
the diameter range of 0-1 pm. with considerable variation within that range among the various experiments (16 19). An aerosol sampling device that combines small acidic particles with larger basic particles on the same flter, thereby giving a single combined measure of acidity, may yield misleading information with respect to biological responses because these two different types of particles will be deposited in different places in the respiratory system. In addition, the dynamics of in situ
neutralization by endogenous ammonia are strongly affected by particle size (20). Because the size of sulfate particles varies with relative humidity (19) which, in turn, varies diurnally, particle size studies should be done with short sampling times. Urban vs. rural aerosol composition. It has been observed that concentrations of acid particles tend to be lower in urban than in nearby rural areas (2, 4, 6, 9, 17). The increased neutralization may not be caused by NH,, however,
since the ion balances imply the presence of an unidentified cation in the urban data. Direct measurements of H+ are compared with inferred levels in Figure 3 for two eastern sites: Whiteface Mountain (24-h averages for one year [21]) and New York City (12-h averages for 25 August days [I71). The line is a regression through the Whiteface data, indicating good agreement between inferred and measured acidity. In New York, although additional neutralization (besides that caused by ammonia) appears to occur (I7), the similarity between the two sites in overall levels of acidity is remarkable, given the large differences in site characteristics. Data from three sites in Toronto (one downtown, two suburban) from the summer of 1986 fall in this same concentration range (9); the acidiq at the downtown site was slightly more neutralized, despite similar NHl+ levels at the sites. Population density may be an important parameter in characterizing both sulfate and ammonium distributions, as may concentrations of other acid and basic species. Because about one third of the U S . population lives in large cities, it is important to monitor in these areas as well as in suburban and rural areas where the aerosol mixture may be less complex. Indoor vs. outdoor aerosols. Substantial additional neutralization has been observed indoors (22). Using these data, we estimated that the average long-term (indoor and outdoor) acid aerosol exposure level in the easternU.S. isabout0.7-1.5fig/m3, which would be further reduced by endogenous (breath) ammonia. Our estimates are intended as an example and are based on a range of sulfate neutralization of 6 7 2 % (4), indoor acidity levels equal to 25 % of outdoor levels (22), and time spent indoors ranging from 75% to 92% (23). It will be important to consider peak and repeated exposures in this same context and to account for indoor sources such as kerosene heaters (24).
Suspected health effects Firm evidence that air pollution can affect health seriously comes from the air pollution episodes of the Meuse Valley in Belgium (1930); Donora, PA (1948); and London (1952), in which excess mortality was clearly demonstrated. Air pollution measurements were sparse during these episodes but the presence of sulfuric acid was strongly suspected in all of them. Notwithstanding this long-held suspicion, the lack of appropriate exposure measurements bas prevented a definitive evaluation of the association of acid aerosol with human health in any Environ. Sci.Technol.,Vol. 23, No. 11, 1989 1319
epidemiological studies completed to date (6). Several past epidemiological studies (25) have postulated an association between sulfates and health responses; however, the evidence for an association between sulfate concentrations and human health effects is inconsistent (26,27). Nevertheless, epidemiological studies that find an association between health and (total) sulfate levels have been cited as supporting the hypothesis that the hydrogen ion is the active agent (2,28). The current direct evidence for acid aerosol health effects thus rests on animal toxicological and human clinical sNdies, some of which are sumnarkd in Table 1. More comprehensive reviews of the health studies are presented in the EPA issues paper (2) and in articles by Shy (29), Graham (30), and Follinsbee (31). Animal studies have identified a variety of endpoints responsive to acid aerosol exposure, ranging from changes in lung clearance rates (32) to changes in lung morphology (33)and rates of cell turnover (34). Human clinical studies have emphasized transient lung function and clearance effects, in response to sulfuric acid at concentrations greater than current ambient levels. Early studies found responses only after exposure to very high levels of H2S04,often in excess of loo0 pg/m3. More recent work has reported responses at lower levels (68100 pg/m3) (35, 36). Exposure times for the reported laboratory studies vary from single doses of less than an hour to repeated doses of a few hours per day (Table 2).
monitoring data indicate that sulfuric react with endogenous ammonia that acid often is not the major acid COnStitu- would otherwise be available to neuent in the ambient environment ( 4 5 , 6, tralize acid particles. 15); moreover, current measurement Responses at ambient levels. Most programs are unable to provide defini- clinical experiments to date have contive information on the aCNd sulfate sidered only concentration levels subcompounds present in an aerosol sam- stantially higher than ambient. It is not ple. It generally has been assumed that clear how to extrapolate responses obH+ is the agent of principal concern ~ ~ under e these d conditions to more and that responses to other acidic spe- realistic (lower) ambient conditions. cies may be estimated by using the H+ Such an extrapolation may be concontribution as a measure of relative founded particularly by endogenous potency, based on responses to H2S04. (breath) ammonia, because experiSome experimental evidence is consist- ments have determined that artificial ent with this hypothesis (32);however, depletion of oral NH3 can enhance the there have also been contradictions. lung function responses obtained at a Schlesinger (32), for example, found given sulfuric acid dose level. Utell et that exposures of rabbits to NI-bHSO4 al. (36) reported an increase of about had significantly less effect on alveolar 150% in the responses of exercising clearance than did equivalent concen- asthmatics when they gargled with trations of H2S04.Thus the question of lemon concentrate before exposure to the similarity of human responses to 350 p g h 3 H2S04.Koenig (39) showed identical H+ loads delivered by means that lun function response to about of differing aerosol compositions re- 70 pg/m$ H2S04 was statistically sigmains an important subject for re- nificant only when the subjects drank search. The existing body of health re- lemonade before exposure, which lowsearch deals almost entirely with ered their oral ammonia levels. The sulfuric acid. abiiity to predict responses to current Effectsof acid gases. Although the ambient acid levels requires further unemphasis to date has been on acid sul- derstanding of the role of endogenous fate particles, it is possible that gaseous ammonia. Effects nf mixtures. Mixtures may acids (HNO,, organic acids) also play a significant role. Koenig et al. (37) be important because acid aerosols do found significant lung function decre- not occur in the ambient air in isolation, ments in adolescent asthmatics exposed and peak levels may coincide with to 0.05 ppm H N 4 . Kleinman et al. those of other pollutants. Data from an(38) have reported a significant syner- imal studies have suggested that synergistic biological response associated gism can occur between high doses of with simultaneous exposures to ozone acid aerosols and other pollutants, such and N a , which in combination will as ozone (34, 40). DaFe metric. Evidence from animal yield HNO, and HNQ. Also, Graham (30) reports acid aerosol responses in studies has been used to support the hyUnresolved health issues the upper airways, which is where pothesis that the total integrated expoResponses to acidic particles other responses are expected from acid sure (concentration x time [C x TI) than sulfuric acid. As shown above, gases. As a last word, acid gases may may be the most appropriate dose measure (6, 12, 32, 33). For lung clearance, there are limited data (32) consistent with this hypothesis; however, TABLE 1 these data also are consistent with an Selected key studies of acid aerosol health effects effect caused by variations in concentration alone, because concentration and integrated exposure are highly corEnd point Subjects FMuUnt related in this data set. The validity of Lung Rabbits H a , 100-1ooO ah3 1-4 hlday (32) clearance the C x T hypothesis needs to be invesNH,HSO, 5W-2MX)pg/m3 2 hlday 2WO~glm~ 2hlday tigated further (301, especially at lower Lung concentrations and longer times, condiclearance, tions for which thresholds due to neuairway tralization by endogenous ammonia responsiveness, airway may be important. The relationships "phology between peak concentratiom and aver. Hist@ aging time are discussed above. pathological Susceptiblesubpopulations. Koenig effects et al. (35) have reported transient changes in lung function among exercising adolescent asthmatics exposed to 68 pg/m3 H2S04; however, replication of this experiment with different groups of exercising adolescent asthmatics failed to confirm this result (39, 42). I I Further research is needed to identify . L
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Environ. Scl.Teohnol..Vol. 23,NO.11,1989
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whether especially susceptible subpop ulations exist. Significance of biological responses. The medical significance of the different symptomatic and biological responses observed in health studies is not always clear and may differ according to health status. For example, the health significance of small transient decrements in lung function is not clear and small transient increases and decreases in lung clearance rates are difficultto interpret (43). Their significance could be clarified through research on biological mechanisms of action and the relationships of such mechanisms to clearly adverse responses in humans. Risk Bssessment needs Although it is not formally a part of EPA’s regulatory procedures for nonhazardous air pollutants, risk assessment has become a useful tool for rationally formulating environmental decisions. Risk assessment can be divided into four steps: hazard identification, dose-response estimation, exposure assessment, and risk characterization (1). Hazard identification ascertains the existence of a potential health concern; this step identifies the types of health responses and the general conditions under which they can occur. The doseresponse estimation step provides a quantitative estimate of the relationship between exposure and effect. Exposure assessment characterizes the exposure(~)of the population for which the risks are to be assessed, the data for this step may come from monitoring or from model estimates. Results from the first three steps are entered into the fourth step, risk characterization, to estimate the health risks to a defined pop ulation by applying the estimated doseresponse function. Most of the elements of the first three steps have been discussed above.
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Most of the health effects research to date on acid aerosols has been oriented toward the “hazard identification” stage of risk assessment. As a result, most laboratory exposures have been at levels substantially higher than observed ambient levels. These exposures have emphasized nebulized H2S04, with prescribed particle s u e distributions, with a mean diameter generally less than 1 pm. Health effects studies are needed to refine the deiinition of the specific chemical agents of concern and the existence of threshold concentration levels; for example, those due to neutralization by endogenous NH,. The last step in the risk assessment process integrates the information from the preceding three steps to yield estimates of health risks for specified exposed population groups. This step of the risk assessment process aspires to realism; therefore, the preceding risk assessment steps must provide apprcpriate information and data. The most important needs of this step of the process are validated dose-response curves and detailed exposure profiles. Monitoring data must be available for several microenvironments and in sufficiently small time increments so that appropriate exposure measures can be calculated. To satisfy this step of the risk assessment process, doseresponse experiments must be carried out at levels near ambient and for those acid aerosols and their mixtures that actually are present.
concluding remarks The available data indicate that acidic aerosols occur in the eastern U.S.on a regular basis. Much remains to be done to characterize the extent of population exposures and their potential health significance. The following questions a p pear to be relevant to this task What species should be measured? What particle sues are important?
What averaging times are important? Are co-pollutants important? It appears that the major gaps in ambient exposure characterization include detailed particle size resolution and speciation for periods less than 24 h, sampling in major eastern population centers, and indoor sampling. The major health effects question is, What are the doseresponse relationships at conditions similar to current actual population exposures? Because current population exposures are defined only approximately, there are important interactions among these key questions. As the research community develops its research program on acid aerosols, we hope that particular attention will be given to these issues. Their resolution can only facilitate the final decision on listing acid aerosols as a criteria pollutant. Acknowledgments This research was sponsored in part by the Electric Power Research Institute and in part by the U S . Department of Energy (Officeof Program Analysis); however, no officialendorsement by any private or governmental agency should be inferred. We are indebted to the many individuals who supplied data, to the reviewers for useful comments, to M. L. Daum for assistance with some of the calculations, and to R. L. Tanner for comments on the analytical chemistry aspects. This article was reviewed for suitability as an ES&T feature by Lawrence J. Folinsbee, C-E Environmental, Inc., Chapel Hill,NC 27514; lack D. Hackney, University of Southern California, Downey, CA 90242; Paul Lioy, University of Medicine and Dentistry, Piscataway, NJ 08854; and Morton Lippmann, New York University Medical Center, New York, NY 10016. References ( I ) “Risk Assessment in the Federal Government: Managing the Process”; NAS Committee on lhe Institutional Means for Assessment of Risks to Public HealU1, National Academy Press: Washington, DC, 1983. (2) “Acid Aerosols Iswe Paper”; U. S. Environmental Protection Agency. U.S. €PA Offce of Health and Environmental Assessment. US. Government Printing Office: Washington, DC, 1988;EPA-600-8-
88-005A.
(3) “Acid Aerosols,” Envimn. Healrh Persuecr. 1989. 79. 3-205. (4) iipfert, E iV “Exposure to Acidic Sulfates in the Atmosphere”; EA-6150, Electric Power Research Institute: Palo Alto. CA. 1988. ( 5 ) Tanner, R: L. In Methods ofAir Sompling and Analysis, 3rd ed.; 1.P Lod e Ed Lewis: Chelsea, MI, 1989; pp. Ai-14:’ (6) Lioy, P 1.; Waldman, I. M. Environ. Health Perspecr. 1989, 79, 15-34. (7) Koutrakis, P. M.; Wolfson, J. M.; Spengler, I. D. Annos. Environ. 1981, 22, 157-62. (8) Paur, R. I.; McLenny, W. A. Presented at the EPAIAPCA Sympasium on Measurement of Toxic and Related Air Pollutants, Raleigh, NC, 1987. (9) Waldman, 1. M.; Lioy. P 1. Amos. Environ. (in press). Environ. Scl.Technol.,Vol.23, No. 11, 1989 1321
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Mueller. P K.: Hidy. G. M. "The Sulfate Regional Experiment: Report of Findings": EPRl EA-1901; Electric Power Rcsearch Institute: Palo Alto. CA. 1983. Mueller. P K.: Watson. I . G . "Eastern Regional Air Quality Measurements": EPRl EA-1914; Electric Power Research Institute: Palo Alto. CA. 19R2. Spengler. 1. D. et a1. Environ. Heolrh Pcnpecr. 1989. 79. 43-51. Tropp. R. J. "Acid Aerosol Measurement Workshop": U S Environmental Protection Agency. Atmospheric Research and Exposure Asrcrrmcnt Laboratory: Research Trianglc Park. NC. 1989: EPAl 60019-891056. Wyrga. R.E.: Lipfert. EW. Presented at the Annual Meeting of the Air and Waste Management Association. Anaheim. CA. June 1989. paper 89-71.3. Schwartz. J. et al. Presented at the Annual Meeting of the Air and Waste Manapemcnt Association. Anaheim. CA, June 1989; paper 89-92.1. Pierson. W. R. et al. Environ. Sci. Technnl. 1987, 21. 679-91. Tanner. R. L. et al. Ann. N . Y Amd. Sei. 1979,322.99-113. Koutrakir. P et al. I n Acid Roin: Scicnrilic rind Technical Advances: S e b e r : London. 1987; pp. 75-82, (19) Koutrakir. I?: Wolfsoon. J. M.: Spngler. I . D. J . Cmph?s. Res. 1989, 9 4 0 5 ) . 6442-48. Larron. T V. Environ. H d r h Perspen. 1989, 79. 7-14. Kclly. T 1. "Trace Gas and Aerosol Measurements at Whiteface Mountain. NY"; Brookhaven National Laboratory: Upton. NY. Reports BNL 37110 (Sept. 1985). BNL 39464 (Jan. 1987). Brsuer. M.: Koutrakis. P;Spngler. J. D. Prcsented at thc Annual Meeting of the Air and Waste Management Association. Anaheim. CA, Junc 1989; paper 89161.1. Johnson. T. "A Study of Human Activity Patterns in Cincinnati. Ohio"; prepared by PEI Associates. Inc. for Elcctric Power Research Institute. Palo Alto. CA.
Environ. Sci. Technol.. VOl. 23.NO. 11. 1989
(38) Kleinman. M. T. et SI.Environ. Health Perspm. 1989, 79. 137-45. (39) Koenig. J. Presented at thc Annual Meeting of the Air and Waste Management Arsociation. Anaheim. CA. June 1989; paper 89-92.4. (40) Lasl. J. A. Environ. Health P ~ r s p m . 1989, 79. 115-19. (41) Kleinman. M. T. Presented at EPRl Work\hop on Acid A c r o ~ o l ~Palo . Alto.
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(42) Linn. W. S . e l al. Am. Ret,. Rerpi,: Di.5..
in press. (43) Spektor. D. M.: Yen. B. M.: Lippmann. M. Ewiron. H d r h Perrprcr. 1989, 79. 167-72.
Fnd HI Lipfert i.s a .sruff member of the Deparrmenr of Applied Science ar Brwkhaven Norional bhoratory (Upton. Long 1,dand. NY) and u parr-rime independenr consultanr. His research inreresrs include air pollution effects. source emissions characterisrics. and energy use topics. tipferr has degrees in mechanical and aeronautical engineeringfrom rhe Universip of Cincinnari. a pnsrgraduare diploma from the von Karma" lnsriture for Fluid DyMmics in BelRium. and a Ph.D. in environmenral srudiesfrom rhe Union Graduare Schwl, Cincinnari.
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(24) Leaderer. B. P et SI.Environ. Sei. Tech""I. (in press). (25) "Health Consequences of Sulfur Oxides: A Report from CHESS. 1970-1971":
U. S. Environmental Protection Agency. U.S. Government Printing Ofice: Washington. DC. May 1974: EPA-65011-74IKkl
(26) Addendum to "Health Consequences of Sulfur Oxides: A Report from CHESS.
1970-1971": U. S. Environmental Protection Agency: Washington. DC. April 19RO: EPA-MW)ll-80-021 (27) Roth. H. D.: Viren. 1. R.: Colucci. A. V. "Evaluation o f CHESS: New York Asthma Data 1970-71": EPRl EA-460: Elcctric Power Research Institute: Palo Alto. CA. 1977. (28) Lippmann. M. Environ. Health Perrpccr. 1989. 79.203.5. (29) Shy. C. M. Environ. Hpolrh Perspecr. 1 9 ~ 9 79. , 187-90. (30) Graham. I . A. Environ. Health Perspecr. 1989. 79. 191-94. (31) Fdmrbee. L. J. Environ. Hcolrh Perspc'ct. 1989, 79. 195-200. (32) Schleringer. R. B. Environ. H d t h Perspcr-r. 1989, 79. 121-27. (33) Gearhart. 1. M.; Schlesinger. R. B. Envimn. Hrnlrh Perspect. 1989. 79. 127-36. (34) Kleinman. M. T et al. Ann. Occup. H?*. 19n8,32. suppi. I. 239-45. (35) Koenig. I . Q . : Covert. D. S.: Pierson. W. E. Environ. Hc-alth Perspccr. 1989, 79, 173-78. (36) Utell. M. J. et al. 1. Aerosol Mcd. 1989. 2. 141-47. (37) Kwnig. J. Q . et al. Am. Rev, Respir. Dir. 1988. 137. A169.
Samuel C. Morris (I) is wirh rhc Biomedical ond En,imnmental Ac.wsimritr Dirision cf Brnokltoven National k~horatory and is also odjenct professor of Engiwering and Public Policy ar Comegie Mellon Universir\: He received his Sc.D. f r . m rhe Graduate Schwl of Public Health. Universiy of Pirtshurgh. Morris is current1v srudying health effecrs of acid aerosols, problems of hazardous- and radiaacrit,ewasre disposal. and ways IO reduce emis-. sions of greenhouse gases.
R o d E. IytLgo (r) Is Manager of rhe Health Studies Program. Environmenr Division, for rhe Elecrric Power Research lnsrirure (EPRI) in Palo Alto. C A . He is also a member of rhe U.S. Environmental Prorecrion Agency Science Advisory Bnard. w q a received his Sc.D. degree in biosratisricsfrom rhe Harvard School of Public Healrh in 1971.
