MM
Airborne Particle Excursions Contributing to Daily Average Particle Levels may be Managed via a 1 hr Standard, with Possible Public Health Benefits
Robert A. Michaels
RAM TRAC CORPORATION, 3100 ROSENDALE ROAD, SCHENECTADY, NY 12309
ABSTRACT. Recent studies associate 24 hr PMy levels within EPA’s 150 .g/M* standard with significantig morbidity and mortality. These findings remain unexplained toxicologically. This study documents the contribution of brief airborne particle excursions to 24 hr average particle levels, and evaluates the possible public health significance of such excursions.
Two proven technologies—inertial and beta attenuation—were identified for continuously monitoring particle mass. Ten 24 hr periods distributed among three locations were examined with PM,9 < 150 g/M®. At all three locations, and in six
of ten days, excursions exceeded 150 g/M?. Excursions of 15 min reached 2000 ug/M®, surpassing the 1952 London foy (PM,o < 1200 xg/M*) and refuting EPA’s assumption that 24 hr averaging protects against excursions.
Toxicology literature confirmed the harmfulness of airborne particles in the range of observed excursions. In contrast, EPA has assumed that protracted postexposure morbidity and mortality are explainable by protracted rather than short-term causes. This study suggests that known toxicological mechanisms involving brief but intense particle mass excursions might cause the unexplained effects.
EPA has advocated rejecting a 1 hr particle standard, citing uncertainty that “the majority of effects” observe} after daily exposure would occur after briefer exposures. However, imposing a 1 hr particle mass limit of 300 «4g/M?® might enhance protection against acknowledged short-term particle effects on public health, while avoiding a burdensome change in the 150 g/M? 24 br mass limit. © 1996 American Association for Aerosol Research. AEROSOL SCIENCE AND TECHNOLOGY 25:437-444 (1996)
INTRODUCTION
At court direction, the U.S. Environmental Protection Agency (EPA) is reviewing the National Ambient Air Quality Standard (NAAQS) for airborne particles (American Lung Association, 1993; American Lung Association, 1994; U.S. District Court, 1994; US. EPA, 1987). The present NAAQS limits particulate matter within a diameter of
Aerosol Science and Technology 25:437—444 (1996) © 1996 American Association for Aerosol Research Published by Elsevier Science Inc.
10 4m (PM,,) to a time-weighted average mass limit of 150 wg /M° of air over 24 hr (and 50 »g/M® annually). It is based primarily upon epidemiological associations of particle elevations during air pollution episodes with elevated mortality and morbidity in communities (for example, see Dockery and Pope, 1994; Pope et al., 1992; Pope and Dockery, 1992). Particle levels
0278-6826 /96 /$15.00 SSDI 0278-6826(96)00102-X
438 R.A. Michaels
during the 1952 London fog have been estimated at 1200 wg/M? (Schwartz, 1993; PM,y < 1200 wg/M*). Recent studies associate significant elevations of morbidity and mortality with particle levels well within the NAAQS (reviewed most recently by EPA, 1996d), and below levels which can be explained by known toxicological mechanisms. The EPA must soon decide whether to control airborne particles to levels below those of demonstrated toxicological significance, and thereby risk further legal challenge.
EPA’s Clean Air Science Advisory Committee (CASAC) advised the EPA to explain the basis for averaging times specified in the airborne particle standard (CASAC, 1995):
“A number of the Panel members noted the absence of a sixth link, namely, the rationale for using a 24-hour averaging time for the NAAQS... . The justification for using any specific averaging time, including a 24-hour averaging time, is not established” (p. 3).
In response, the Agency considered applying a longer averaging time of up to several days and a shorter averaging time, such as 1 hr (U.S. EPA, 1996a; U.S. EPA, 1996b; U.S. EPA, 1996c; U.S. EPA, 1996d). Shortterm average particle levels may be several times the corresponding daily averages (Waller and Commins, 1966). The present study inquires whether 24 hr average particle levels educed via the U.S. EPA reference gravimetric monitoring method might encompass undetected shorter term excursions which might represent a candidate explanation of the observed adverse human health effects.
METHODS
This investigation evaluated available analytical data and literature to resolve three issues. First, it determined whether instrumentation is available to reliably and economically measure particle levels over short intervals. Second, it quantified short-term
Aerosol Science and Technology 25:4 November 1996
excursion of particle mass contributing to 24 hr averages well within the NAAQS. Third, it compared documented short-term excursions with longer term particle excursions unequivocally associated with toxicological action, for example, as observed in such past mortality events as the 1952 London fog.
The findings regarding the three issues elucidated above were evaluated relative to EPA policies and procedures for air pollutant standard setting under the Clean Air Act (American Thoracic Society, 1985; U.S. EPA, 1989) based upon the weight of evidence for the existence, nature, and magnitude of public health risks. Ultimately, the findings were evaluated relative to a major regulatory issue facing state health departments and the U.S. EPA. That issue is whether, in view of currently available data and instrumentation technologies, public health protection can be assured via the current airborne particle risk management approach, which limits particle excursions only to the limited degree that their occurrence might produce exceedances of 24 hr and annual mass limits.
FINDINGS Identification of Monitoring Technologies
Two relatively new particle monitoring technologies were found to be capable of reliably measuring airborne particle levels in real time or over short intervals (Chow, 1995a; Chow, 1995b; Meyer, 1993; Meyer et al., 1995; Michaels, 1995a; Michaels, 1995b; Patashnick and Rupprecht, 1991; RAM TRAC, 1995; R&P, undated, a; R&P, undated, b; R&P, 1994; Rupprecht et al., 1995a; Rupprecht et al., 1995b; U.S. EPA, 1995b). Inertial monitors can measure particles virtually continuously, whereas beta attenuation monitors can do so over intervals of an hour or less under realistic conditions. Both technologies represent alternatives to the reference gravimetric method for monitoring airborne particles. The technologies reflect evolution of the older technologies most notably in three directions:
Aerosol Science and Technology 25:4 November 1996
1) toward greater sensitivity associated with utilizing nongravimetric physical principles for measurement, 2) toward continuous monitoring and reduced sampling time, and 3) toward greater automation and reduced expense of operation. Indeed, inertial instruments are deployed in the U.K. Automatic Particulate Monitoring Network (AUN), gathering particle data with a 15 min time resolution (Rupprecht et al., 1995a).! This short time resolution adds power to ongoing U.K. studies of particle health effects.
Detection of Airborne Particle Excursions
Data sets were screened to identify those which: 1) were obtained using one or both of the identified technologies, 2) exhibited
'The 15 min resolution enables AUN to publish 1 hr average values at monitors in 23 cities on the Internet (http: / / www.acat.co.uk / products / centres/ netcen/ airqual/bulletins/pm10.html), and to update these published airborne particle mass values hourly.
Managing Airborne Particle Excursions 439
short time resolution, 3) encompassed at least one 24 hr period, and 4) revealed 24 hr airborne particle levels within the curtrent NAAQS. Screening identified three locations and ten days, during which 24 hr average PM,, < 150 a¢g/M®. At all three locations, and in six of the ten identified cases meeting the screening criteria, excursions exceeding 150 wg/M? were noted (Fig. 1, Table 1).
In Birmingham, AL on April 16, 1990, 24 hr average PM) was 70 ug/M’, but two 1 hr average excursions exceeding 200 yg /M? were recorded (Table 1). In Penticton, British Columbia, on approximately eight days between July 30 and August 7, 1994, 24 hr average PM,, varied from close to zero to close to 150 wg/M?, but excursions exceeding 150 4g/M? were recorded on four of the eight days (Fig. 1, Table 1). These included three 1 hr average excursions to 300 xg/M? and two excursions to approximately 500 ~g/M°. In Zeebrugge, Belgium, on March 15, 1993, 24 hr average PM, was 101 pg/M®, but several 15 min
Jee Average PM-10
. Aol 100
1-Hour and 24-Hour PM-10 Cone [yg/m']
\W
wn
| 24-Hour Average PM-10
S094 S1-Ju-94 T-Aug-94 22-Aug-94
S-Aug-94
4-Aug-94 S-Aug-94 6 Aug-94 ——7-Aug-94
Time
*source:
Rupprecht, E., M. B. Meyer, and H. Patashnick. Performance characteristics of a near real-time, ‘particulate mass monitor. Conference on Particulate Matter: Health and Regulatory Issues. Pittsburgh, Pennsylvania 4-6 April 1995.
FIGURE 1. Hourly and daily PM) concentration in Penticton, British Columbia, July 30—August 7, 1994.*
440 R.A. Michaels
Aerosol Science and Technology 25:4 November 1996
TABLE 1. Short-Term Particle Excursions Without Exceedance of the 24 hr PM-10 Standard
Location Source Date
24 br Airborne Excursion- ExcursionAverage Particle Excursion to-24-hr to-1952 Particle Mass Averaging Mass London-Fog
Mass Excursion Time Ratio Ratio**
= = — (yg/cuM) (yg/cuM) (min) — ad
Zeebrugge, Belgium 1 3/15/93 Penticton, British Columbia 3. 7/31/94 Zeebrugge, Belgium 1 3/15/93 Zeebrugge, Belgium 1 3/15/93 Zeebrugge, Belgium 1 3/15/93 Penticton, British Columbia 3 8/1/94 Zeebrugge, Belgium 1 3/15/93 Zecbrugge, Belgium 1 3/15/93 Penticton, British Columbia 3 8/1/94 Birmingham, Alabama 2 4/16/90 Birmingham, Alabama 2 4/16/90 Penticton, British Columbia 3 8/2/94 Penticton, British Columbia 3 8/1/94 Zeebrugge, Belgium 1 3/15/93 Birmingham, Alabama 2 4/16/90 Penticton, British Columbia 3 8/3/94 Zeebrugge, Belgium 1 3/15/93 Zeebrugge, Belgium 1 3/15/93 Zeebrugge, Belgium 1 3/15/93 Zeebrugge, Belgium 1 3/15/93 Penticton, British Columbia 3 8/2/94 Penticton, British Columbia 3 8/3/94 Zeebrugge, Belgium 1 3/15/93 Zeebrugge, Belgium 1 3/15/93 Zeebrugge, Belgium at 3/15/93 Penticton, British Columbia 3 8/3/94 Zeebrugge, Belgium 1 3/15/93 Summary
Excursions detected PAE Mean excursion ( wg /cu-M) = Standard deviation (wg /cu-M) Coefficient of variation Locations examined 3 Fraction exhibiting excursions 1.00 Days examined 10 Fraction exhibiting excursions 0.60
101 1898 15 18.8 1.6
50 500 60 10.0 0.4 101 780 15 Te: 0.7 101 648 15 6.4 0.5 101 553 a5 55 0.5 100 460 60 4.6 0.4 101 425 15 4.2 0.4 101 355 15 35 0.3 100 320 60 3.2 0.3
70 222 60 3.2 0.2
70 208 60 3.0 0.2 120 350 60 2.9 0.3 100 280 60 2.8 0.2 101 283 15 2.8 0.2
70 176 60 2.5 0.1 120 290 60 2.4 0.2 101 238 15 2.4 0.2 101 230 15 233 0.2 101 220 15 2.2 0.2 101 220 15 22: 0.2 120 250 60 21 0.2 120 240 60 2.0 0.2 101 195 15 1.93 0.2 101 193 15 1.9 0.2 101 185 15 1.8 0.2 120 210 60 18 0.2 101 153 15 1.5 0.1
Birmingham, 3/1 day; Penticton, 9/9 days; Zeebrugge, 15/1 day
99 373 3.9 0.3 17 342 — 3.6 0.3 17 91 92 91
"Sources: adapted from: 1. Institute of Hygiens 2. Meyer, M. B. Apj the 90s. Scottsdale, AZ, Jan. 1993.
ind Epidemics, Belgium.
tions of continuous PM-10 measurements. Conference on the Role of Meteorology in Managing the Environment of
3. Rupprecht, E., Meyer, M. B., and Patashnick, H. Performance characteristics of a near real-time particulate mass monitor. Conference on Particulate Matter: Health and Regulatory Issues, Pittsburgh, PA, Apr. 1995.
** Conservatively assumes London fog = 1200 2g/cu M, but this estimate is probably total particulates rather than only PM-10. The deaths of approximately 4000 people over ten days in 1952 have been attributed to the London fog (see text for source).
average excursions exceeding 200 4g/M? were recorded (Table 1). In one excursion, the 15 min average reached nearly 2000 pe/M, significantly exceeding the estimated magnitude, although not the persistence, of the 1952 London fog (< 1200pe /M?; Schwartz, 1993).
Comparison of Excursions with Levels of Known Toxicity
Particle levels in the observed range of reported fine particle excursions have caused adverse health effects. Studies involving animals have revealed clinically sig-
Aerosol Science and Technology 25:4 November 1996
nificant short-term particle effects, including mortality (Godleski, 1995; Godleski et al., 1996; Nearing et al., 1996a; Nearing et al., 1996b). Numerous studies of shortterm effects exerted by airborne particles during controlled acute human exposures have also reported positive results (Anderson et al., 1992; Aris et al., 1991a; Aris et al., 1991b; Avol et al., 1988a; Avol et al., 1988b; Avol et al., 1990; Balmes et al., 1988; Culp et al., 1996; Dockery and Pope, 1994; Fine et al., 1987a; Fine et al., 1987b; Framptom et al., 1992; Framptom et al., 1996; Green et al., 1989; Hanley et al., 1992; Koenig et al., 1989; Koenig et al., 1992; Koenig et al., 1993; Koenig et al., 1994; Kulle et al., 1986; Laube et al., 1993; Linn et al., 1989; Morrow et al., 1994; Utell et al., 1982; Utell et al., 1989; Yang and Yang, 1994). In addition to these clinical studies, Lawther et al. (1970) conducted an epidemiological study employing a diary method in which bronchitis patients recorded daily changes in the severity of their symptoms relative to their recollection of previous-day symptom severity. Lawther et al. reported an association of symptom severity with previous-day concentrations of smoke or sulfuric acid in London. Based upon experiments on normal subjects, they attributed the association to peak rather than 24 hr average exposure levels. Briefly intense exposures have been reported to overcome pulmonary clearance mechanisms (Miller et al., 1995). Some excursions reported in the present study greatly exceed levels observed in reports cited above. Table 1 compares the excursions to a more conservative toxicological benchmark: the estimated particle level during the deadly 1952 London fog. Excursions attained levels from 0.1 to 1.6 times this benchmark, with four of 27 (15%) reaching at least 0.5 of the London fog level.
CONCLUSIONS AND DISCUSSION
The findings of this study form the basis for drawing three conclusions about airborne particles: 1) excursions of airborne particle
Managing Airborne Particle Excursions 441
mass may elevate PM,, by an order of magnitude relative to 24 hr average levels within the 150 u4g/M* NAAQS, 2) particle levels comparable to those reached during documented excursions have exerted toxicological effects in animal and clinical studies, and 3) excursions might constitute a previously unrecognized cause of unexplained mortality and morbidity revealed by epidemiology studies involving 24 hr particle levels.
The U.S. EPA’s NAAQS requires PMj9 mass over 24 hr and one year, precluding both detection and control of shorter term exposures. One implication of the present investigation is that the Agency should further consider the short-term causation scenario for standard setting. The findings reported in epidemiological and controlled human exposure studies must be evaluated relative to EPA policies and procedures for air pollutant standard setting (American Thoracic Society, 1985; U.S. EPA, 1989) based upon the weight of evidence for the existence, nature, and magnitude of public health risks. The Agency requested the American Thoracic Society to define toxicological effects, and degrees of effect, which might qualify to form the basis for limiting air pollutants, and both the American Thoracic Society (1985) and the U.S. EPA (1989) have published these guidelines. Their implementation leaves much to discretion; nonetheless, the guidelines are prescriptive and valuable.
According to U.S. EPA policy (U.S. EPA, 1989), air pollution limits must be set based upon a clinically significant adverse effect, not any effect, as defined by American Thoracic Society (1985):
“We define ‘adverse respiratory health effects’ as medically significant physiological or pathologic changes...” (p. 666).
Many controlled human exposure studies focus upon asthmatics during exercise and at rest, revealing symptoms of asthma exacerbation, such as bronchoconstriction, increased airway resistance, reduced FEV, and FEV;, reduced FVC, and reduced peak
442 R.A. Michaels
flow. Whether such effects can form the basis for air pollutant standard setting under EPA’s Clean Air Act implementation policies and procedures is addressed by the American Thoracic Society (1985):
“the eye, nose, and throat irritation associated with ... urban ‘smog’ or photochemical oxidant air pollution is not medically important and is, therefore, not considered an ‘adverse health effect’ in relation to the Clean Air Act. This irritation certainly is annoying or bothersome, which puts it in the category of an effect on human welfare. However, irritation that triggers an asthmatic attack is an adverse health effect” (p. 666; emphasis added).
Symptoms evoked by controlled clinical exposures do not include triggering an asthmatic attack. However, according to the guidelines, this clinical endpoint need not be experimentally induced to be used in standard setting. Rather, the guidelines justify inferring greater severity of response with greater exposure:
This spectrum of biological responses would be evoked more strongly as the concentrations of pollutants are increased” (American Thoracic Society, 1985, p. 666; emphasis added).
The U.S. EPA has proposed to regulate PM, rather than PM,, (U.S. EPA, 1995a). This proposal is irrelevant to the present findings made or conclusions drawn. Effects exerted by particles are widely acknowledged to result predominantly from the most respirable (fine) fraction. PMj9 excursions undoubtedly encompass excursions of PM, ,. Thus, the 24 hr PM,, standard of 150 4g/M? can be expressed as an equivalent 1 hr standard of about 300 pg/M?, which may be in turn formulated as a 1 hr PM,; mass equivalent if the NAAQS focus changes. Thus, a 1 hr airborne particle mass limit is consistent with the Agency’s proposed risk management strategy and its standard-setting guidelines. The present study further suggests that a 1 hr standard may eliminate the need to
Aerosol Science and Technology 25:4 November 1996
tighten longer term limits while being: 1) effective at protecting public health, 2) justified by available data, and 3) economically feasible.
This research was supported by Rupprecht & Patashnick, Inc., Albany, NY.
References
American Lung Association (1993). Complaint in a civil case: American Lung Association vs. Carol Browner, U.S. EPA; U.S. District Court, District of Arizona, Case No. CIV-93-643TUC-ACM, 11 pp.
American Lung Association (1994). The Perils of Particulates. New York City, 24 pp.
American Thoracic Society (1985). Amer. Rev. Respiratory Disease 131:666—668.
Anderson, K. R. et al. (1992). J. Air & Waste Management Association 42:770-776.
Aris, R. et al. (1991a). Amer. Rev. Respiratory Disease 143:85-91.
Aris, R. et al. (1991b), Amer. Rev. Respiratory Disease 143:744-750.
Avol, E. L. et al. (1988a). Toxicology and Industrial Health 4:173-184.
Avol, E. L. et al. (1988b). J. Air Pollution Control Association 38:258-263.
Avol, E. L. et al. (1990). Amer. Rev. Respiratory Disease 142:343-348,
Balmes, J. R. et al. (1988). Amer. Rev. Respiratory Disease 138:35—39.
CASAC (1995). Letter from George T. Wolff, CASAC Chairperson, to EPA Administrator Carol M. Browner transmitting CASAC comments on the April 1995 draft Air Quality Criteria for Particulate Matter. Washington, DC, Clean Air Science Advisory Committee (CASAC), EPA-SAB-CASAC-LTR-95-005, 4 Pp-
Chow, J. C. (1995a). Environmental Manager 112-15.
Chow, J. C. (1995b). J. Air & Waste Management Association 45(5):320-382.
Culp, D. L. et al. (1996). Amer. J. Physiology.
Dockery, D. W. and Pope, C. A. III (1994). Annual Rev. Public Health 15:107-132.
Fine, J. M. et al. (1987a). Amer. Rev. Respiratory Disease 135:826-830.
Aerosol Science and Technology 25:4 November 1996
Fine, J. M. et al. (1987b). Amer. Rev. Respiratory Disease 136:1, 122-126.
Framptom, M. W. et al. (1992). Amer. Rev. Respiratory Disease 146:626-632.
Framptom, M. W. et al. (1996). Environmental Res.
Godleski, J. J. (1995). Oral and written report to the PM,) Review Panel, U.S. EPA Clean Air Science Advisory Committee (CASAC), Research Triangle Park, NC.
Godleski, J. J. et al. (1996). Death from inhalation of concentrated ambient air particles in animal models of pulmonary disease. New Orleans, LA, American Thoracic Society 1996 International Conference, abstract.
Green, D. J. et al. (1989). J. Toxicology and Environmental Health 28:261-275.
Hanley, Q. S. et al. (1992). Amer. Rev. Respiratory Disease 145:326-331.
Koenig, J. Q. et al. (1989). Effects of inhalation of acidic compounds on pulmonary function in allergic adolescent subjects. In Symposium on the Health Effects of Acid Aerosols. Research Triangle Park, NC, Oct. 1987. Environmental Health Perspectives 79:173-178.
Koenig, J. Q. et al. (1992). Toxicology and Industrial Health 8:285-296.
Koenig, J. Q. et al. (1993). Archives of Environmental Health 48:171-175.
Koenig, J. Q. et al. (1994). Oxidant and acid aerosol exposure in healthy subjects and subjects with asthma. Part 1: Effects of oxidants, combined with sulfuric or nitric acid, on the pulmonary function of adolescents with asthma. Cambridge, MA, Health Effects Institute, Research Report No. 70, 36 pp.
Kulle, T. J. ct al. (1986). Environmental Res. 41:239-250.
Laube, B. L. et al. (1993). Amer. Rev. Respiratory Disease 147:1, 105-111.
Lawther, P. J., Waller, R. E., and Henderson, M. (1970). Thorax 25:525-539.
Linn, W. S. et al. (1989). Amer. Rev. Respiratory Disease 140:161-166.
Meyer, M. B. (1993). Applications of continuous PM, 9 measurements. Paper presented at the Conference on the Role of Meteorology in Managing the Environment. Scottsdale, AZ, 12 pp.
Meyer, M. B., Rupprecht, E., and Patashnick, H. (1995). Considerations for the sampling and measurement of ambient particle mass. Paper
Managing Airborne Particle Excursions 443
presented at the U.S. EPA and Air & Waste Management Association Conference on Particulate Matter: Health and Regulatory Issues. Pittsburgh, PA, 8 pp.
Michaels, R. A. (1995a). Response to Chow (1995a, 1996b). In J. G. Watson, J. Air & Waste Management Association 45:666-684,
Michaels, R. A. (1995b). Health risks and particle monitoring: New technologies to meet emerging data needs. In AAAR ’95. Pittsburgh, PA, 14th Annual Meeting of the American Association for Aerosol Research, Abstract, p. 338.
Miller, F. J. et al. (1995). Dosimetric issues relating to particulate toxicity. In R. F. Phalen and D. V. Bates (eds.), Proceedings of the Colloquium on Particulate Air Pollution and Human Mortality and Morbidity, Part I; Irvine, CA; Inhalation Toxicology 7:615—-632.
Morrow, P. E. et al. (1994). Annals of Occupational Hygiene, 38(Suppl. 1):933-938.
Nearing, B. D. ct al. (1996a). Inhaled fly ash results in alteration in cardiac electrophysiologic function. New Orleans, LA, American Thoracic Society 1996 International Conference, Abstract.
Nearing, B. D. et al. (1996b). Exposure to inhaled environmental air particles results in significant ST-segment elevation in dogs with normal coronary arteries. American College of Cardiology 45th Annual Scientific Session, Abstract No. 075548.
Patashnick, H., and Rupprecht, E. G. (1991). J. Air & Waste Management Association 41(8):1079-1083.
Pope, C. A. Schwartz, J., and Ransom, M. R. (1992). Archives of Environmental Health 47(3):211-217.
Pope, C. A., and Dockery, D. W. (1992). Amer. Rev. Respiratory Disease 145:1,123-128.
RAM TRAC (1995). Health risks and particle monitoring: New technologies to meet emerging data needs, including a one-hour upper mass limit in the next national ambient air quality standard. R. A. Michaels, Ph.D., CEP, Project Director. Schenectady, NY, RAM TRAC Corporation, 169 pp.
R&P (undated, a). TEOM® Series 1400A ambient particulate monitor. Albany, NY, Rup-
precht and Patashnick Company, product technical literature, 4 pp. plus attachments.
444 R.A. Michaels
R&P (undated, b). Partisol Model 2000 air sampler. Albany, NY, Rupprecht and Patashnick Company, product technical literature, 4 pp. plus attachments.
R&P (1994). Summary: Series 5400 ambient carbon particulate monitor. Albany, NY, Rupprecht and Patashnick Company, product technical literature, 11 pp. plus attachments.
Rupprecht, E., Meyer, M. B., and Patashnick, H. (1995a). Performance characteristics of a near real-time ambient particulate mass monitor. Paper presented at the U.S. EPA and Air & Waste Management Association Conference on Particulate Matter: Health and Regulatory Issues. Pittsburgh, PA, 11 pp.
Rupprecht, G. et al. (1995b). A new automated monitor for the measurement of particulate carbon in the atmosphere. Paper presented at the U.S. EPA and Air & Waste Management Association Conference on Particulate Matter: Health and Regulatory Issues. Pittsburgh, PA, 11 pp.
Rylander, R. (1969). Archives of Environmental Health 18:551-555.
Schwartz, J. (1993). Environmental pollution and human health: An epidemiology perspective. In C. R. Cothern and N. P. Ross (eds.), Environmental Statistics, Assessment, and Forecasting. Boca Raton, FL, Lewis, ch. 11., pp. 209-222.
US. District Court (1994). Judgment in a civil case: American Lung Association vs. Carol Browner, U.S. EPA; U.S. District Court, District of Arizona, Case No. CIV-93-643-TUCACM, 11 pp.
U.S. EPA (1987). Ambient air quality standards for particulate matter; Final rules. Federal Register 52(126):24, 633-668.
U.S. EPA (1989). Interim Methods for Development of Inhalation Reference Doses. Washing-
Acrosol Science and Technology 25:4 November 1996
ton, DC, Office of Health and Environmental Assessment, EPA /600/8-88/066F, PB90-145 723, i. p.
U.S. EPA (1996a). Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information: OAQPS Staff Paper. Research Triangle Park, NC, Office of Air Quality Planning and Standards (OAQPS), External Review Draft, i. p.
U.S. EPA (1996b). Air Quality Criteria for Particulate Matter. Washington, DC, Office of Research and Development, EPA/600/P95/001a, Vol. 1 of 3 volumes, i. p.
U.S. EPA (1996c). Air Quality Criteria for Particulate Matter. Washington, DC, Office of Research and Development, EPA/600/P95/001b, Vol. 2 of 3 volumes, i. p.
U.S. EPA (1996d). Air Quality Criteria for Particulate Matter. Washington, DC, Office of Research and Development, EPA/600/P95/001c, Vol. 3 of 3 volumes, i. p.
Utell, M. J. et al. (1982). Comparison of normal and asthmatic subjects’ responses to sulphate pollutant aerosols. In W. H. Walton (ed.), Inhaled Particles. V. Proceedings of an International Symposium, organized by the British Occupational Hygiene Society, Cardiff, Wales, Sept. 1980. Annals of Occupational Hygiene 26:691—-697.
Utell, M. J. et al. (1989). J. Aerosol Med. 2:141-147.
Waller, R. E. and Commins, B. T. (1966). Episodes of high pollution in London, 1952-1966. In National Society for Clean Air, London, Proceedings of the International Clean Air Congress, London, 1966, Part 1, p. 228.
Yang, S.-C., and Yang, S.-P. (1994). Archives of Environmental Health 49:182-187.
Received January 10, 1996.
Publication citation
Michaels, RA. Airborne particle excursions contributing to daily average particle levels may be managed via a one-hour standard, with possible public health benefits. Aerosol Science and Technology, 25:437-44, November 1996;