Uml«d SUt«s Olfta*
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EPA-SAB/CASAC-89-001
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. D.C. 20460
October 6, 1988
OFFICE OF
THE ADMINISTRATOR
Dr. Roger McClellan, Chairman
Clean Air Scientific Advisory Committee
Science Advisory Board (A-101F)
U.S. Environmental Protection Agency
Washington, DC 20460
Dear Dr. McClellan;
This letter transmits the conclusions of the CASAC Acid
Aerosol Subcommittee concerning listing acid particles as a
criteria pollutant. The Subcommittee met on June 14-15, 1988 in
Washington, DC to review the draft "Acid Aerosols Issue Paper"
(EPA/600/8-88/005A) prepared by EPA's Office of Research and
Development.
The Subcommittee concensus, although not unanimous, was that
CASAC recommend to the Administrator that he consider listing
acid particles under Section 108 of the Clean Air Act, In
the Subcommittee's view, the cumulative evidence provided by the
available animal, controlled human exposure, and epidemiologic
studies clearly suggests possible health effects associated
with exposure to acid particles. The Subcommittee recognizes
that the available data base is not complete but is concerned
by the potential health risks resulting from exposures under
typical ambient conditions. The -Subcommittee conculded that
the weight of the evidence from the disciplines of animal
toxicology, controlled clinical studies, and epidemiology is
sufficient at this time t© recommend that the Administrator
consider listing of acid particles as a criteria pollutant.
In summary, it should be noted that the majority vote was
cast on the basis of the weight ©f the evidence from the three
health related disciplines rather than on any single study.
A more detailed discussion of the Subcommittee position is
included in the attached report.
Sincerely,
Mark J. Utell, MD
Chairman
Acid Aerosol Subcommittee
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ACID AEROSOL SUBCOMMITTEE
RECOMMENDATIONS TO THE
CLEAN AIR SCIENTIFIC ADVISORY COMMITTEE
ON
POSSIBLE LISTING OF ACID AEROSOLS AS A CRITERIA AIR POLLUTANT
FINAL SUBCOMMITTEE REPORT
OCTOBER 6, 1988
U.S. ENVIRONMENTAL PROTECTION AGENCY
SCIENCE ADVISORY BOARD
WASHINGTON, DC
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ABSTRACT
Under Section 109 of the Clean Air Act, the U.S.
Environmental Protection Agency (EPA) is required to periodically
review national ambient air quality standards (NAAQS) and the
criteria on which they are based. The Act also requires the
Clean Air Scientific Advisory Committee (CASAC) to provide
scientific advice on any additional knowledge that is required to
evaluate existing, or setting new or revised NAAQS. To evaluate
the health effects of the class of air pollutants known as acid
aerosols, the Committee requested that EPA prepare an "Acid
Aerosol Issue Paper". This Issue Paper was reviewed by the Acid
Aerosol Subcommittee of CASAC in June 1988. This report presents
the conclusions and recommendations of that Subcommittee as
transmitted to the CASAC.
Key. Wordsj_ acid aerosols, acid particles, NAAQS
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U.S. Environmental Protection Agency
NOTICE
This report has been written as part of "he activities of
the Science Advisory Board, a public advisory group providing
extramural scientific Information and advice to the Administrator
and other officials of the Environmental Protection Agency. The
Board Is structured to provide a balanced expert assessment of
scientific matters related to problems facing the Agency. This
report has not been reviewed for approval by the Agency; and,
hence, the contents of this report do not necessarily represent
the views and policies of the Environmental Protection Agency or
other agencies in the Federal Government. Mention of trade names
or commercial products do not constitute a recommendation for
use.
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TABLE OF CONTENTS
1.0 BACKGROUND 1
2.0 OPTIONS FACING THE SUBCOMMITTEE 1
3.0 MAJOR RESEARCH FINDINGS THAT SUPPORT
THE SUBCOMMITTEE RECOMMENDATIONS ..... 2
4.0 REVIEW OF THE ISSUE PAPER 3
5.0 SUBCOMMITTEE RECOMMENDATIONS TO CASAC . . 3
5.1 Recommendation to Defer Decision . . 4
5.2 Recommendation Not to List 4
5,3 Majority Conclusions - Recommendation
to List 5
6,0 LITERATURE CITED 6
APPENDICES
A - Roster of the CASAC Acid Aerosol
Subcommittee
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U.S. Environmental Protection Agency
Clean Air Scientific Advisory Committee
Acid Aerosol Subcommittee
Recommendations on Listing Acid
Particles as a Criteria Pollutant
1-0 Background
Under section 109(d) of the Clean Air Act the EPA must
periodically review the national ambient air quality standards
(NAAQS) and the air quality criteria on which they are based, and
must revise such criteria and standards as appropriate. In the
process of reviewing new scientific studies concerning health
effects of particulate matter and sulfur oxides in 1986, it
became apparent that researchers had identified acid aerosols as
a constituent of the airborne mix of these pollutants that may be
associated with observed health effects. As a result, the Clean
Air Scientific Advisory Committee (CASAC) recommended that the
Agency prepare an Acid Aerosols Issue Paper to evaluate the
emerging literature concerning health effects directly associated
with acid aerosols.
The Agency completed this draft Issue Paper in early 1988
and presented it to the CASAC Acid Aerosol Subcommittee on June
14-15! 1988. The Subcommittee faced three primary tasks.
First, whether available scientific information provided
sufficient and compelling evidence for a listing of acid
particles as a prelude to development of a separate criteria
pollutant, second, to assess the adequacy of the Issue Paper,
and third, to identify and prioritize research needed to
respond to the critical issues identified in the draft Issue
Paper as well as any additional issues identified by the
Subcommittee itself. The first and second issues are addressed
in this report, the third is discussed in a separate research
recommendations report (EPA-SAB/CASAC-89-002).
2.0 Options facing the Subcommittee
In addressing the listing issue, the Subcommittee considered
the three options presented by EPA in the draft Issue Paper:
1) Recommend that the Administrator consider listing
acid aerosols under Section 108 of the Act. This implies a
judgment that the available health effects information is
compelling enough to require additional protection beyond the
current NAAQS, Within 12 months of a listing decision, EPA must
issue air quality criteria and propose standards.
2) Recommend that the Administrator not consider
listing acid aerosols under Section 108 of the Act. The
available health effects information as well as any new research
would be considered during the next review of the particulate
matter standards.
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3) Recommend that the Administrator defer judgment
regarding action to list acid aerosols pending further research
on the critical needs identified in Chapter 8 (Research Needs)
of the draft Acid Aerosols Issue Paper.
In its discussion of research issues, the Subcommittee
considered research needs identified by the Agency in the Issue
Paper, research needs identified by the members of the
Subcommittee, and presentations from' the interested public at
the June 14-15, 1988 meeting.
3.0 Manor Research Findings that Supportjthe_Subcommittee
Recommendations
The majority vote was based on the weight of evidence from
research involving the three disciplines of animal toxicology,
controlled clinical exposures, and epidemiologic studies. The
key findings from recent toxicology research include? in chronic
daily exposures of rabbits (250 pg/m3 for 1-hr/day, 5 days/week
for one year) persistent alterations of mucociliary and
alveolar particle clearance, airway reactivity, airway
secretory cell density and characteristics, and airway
caliber changes were produced (Gearhart and Schlesinger, 1988).
Such changes were similar to those produced by chronic exposure
to cigarette smoke, suggesting that chronic bronchitis could
result from more prolonged exposures. Furthermore, in single
3-hour and 5 days of 3-hour daily exposures to ultrafine acid
coated zinc oxide particles with sulfuric acid concentrations
in the range of 20-30 |ig/B3, guinea pigs developed
persistent changes in vital capacity, airway compliance,
lung permeability, and carbon-monoxide diffusing capacity
(Amdur and Chen, 1988). Similar results were obtained with
200 pg/m3 of ultrafine droplets of pure sulfuric acid. These
findings suggest that primary and secondary sulfuric acid
occurring as coatings on ultrafiii® fly ash particles may
be considerably more toxic than secondary acidic aerosol which
is found in the atmosphere in solution droplets.
Recent data from controlled clinical studies lends
additional support for a relationship between exposure to near
ambient levels of acid aerosols and adverse respiratory effects.
In 1983, Koenig et al., (1983) identified allergic adolescent
asthmatics as a subgroup responsive to inhalation of 100 pg/nr
sulfuric acid aerosols (30 minutes at rest followed by 10 minutes
of exercise). These researchers have extended further their
observation in allergic adolescent asthmatics linking exposure to
near ambient levels of sulfuric acid at 68 jig/m3 with significant
alterations in lung function (Koenig et al., 1988). The FEV^
decreased 6% after inhalation of sulfuric acid using the
previously described exposure protocol vs 1% decrease after
breathing air. Furthermore, the most recent findings from Bauer
et al. (1988) support Koenig'a findings in that adult allergic
asthmatics showed greater decrements in FEY^ breathing 75 pg/m
sulfuric acid vs. NaCl (control) for 2 hours in an environmental
chamber. Based on our understanding of the current
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data base, extrapolation to longer exposures coupled with
more rigorous exercise could serve to intensify the response.
Data linking acid aerosols with respiratory health
effects emerges from the ongoing field studies. Speizer
(1988) showed that bronchitis in 10-12 year old children in
four U.S. cities varied from about 3-11% from standardized
questionnaire responses in direct relation to annual average
concentration of aerosol H4", with the highest prevalence in the
community with the highest annual average H+ concentration
which was 1.8 ug/mj (expressed as sulfuric acid
equivalents). Similar associations were seen for other
respiratory symptom responses in the same population. While the
prevalence data were for the 1981 school year and the
concentration data were for 1985-1988, it has been
established in other studies from the six cities group that the
bronchitis prevalence in these cities were in similar
proportion in this population in other years, and that there
was little variation in annual average pollution levels during
these years. There were occasional exceedences of the current
NAAQS for PM and SO, in some of these communities during some of
the years coverea by these studies, nevertheless, the
Subcommittee is concerned that the current MAAQS may not
provide adequate protection against such health effects.
4.0 Review of Issue Paper
The draft Issue Paper was generally considered to be well
prepared and comprehensive. Most members of the Subcommittee
provided detailed written comments concerning the draft to the
Agency during and following the June 14-15, 1988 meeting.
Extensive discussion occurred during the meeting which pointed
out the need to address certain issues further. An example of
such an issue is to define the pollutant indicator to regulate,
its form, and measurement methodology.
5.0 Subcommittee Recommendations to CASAC
Following a careful review of the Issue Paper and extensive
deliberations, members of the Subcommittee voted and reached the
nearly unanimous conclusion1 that the Clean Air Scientific
Advisory Committee should recommend that the Administrator
consider listing acid particles as a criteria pollutant.
However, one Subcommittee member was in favor of recommending
that the Administrator not consider listing acid particles, and
one member was in favor of recommending that the Administrator
defer such a decision until further research was completed.
The minority positions are presented first.
The Subcommittee vote wass 9 in favor of recommending that the
Administrator consider listing, 1 in favor of recommending
that the Administrator not consider listing, and 1 in favor
of recommending that the Administrator defer judgment
pending further research.
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5.1 Recommendation to Defer Decision fDr. Robert Phalen^
1) -Although there is scientific evidence that airborne
acidity at or near levels found in the environment is capable of
harming respiratory tract tissues, I recommend that the decision
to list acid aerosols as a NAAQS be deferred pending further
research directed at resolving several basic issues. First, it
is not at all clear just what the relevant air contaminant is.
Airborne acidity can be in vapor forms and in particulate forms.
In some cases, the acid vapor exceeds the particles in total
mass. The full combination - that is the total acid present in
all forms - is the logical agent to consider for listing because
that is what is inhaled* This is also valid scientifically as
many of us believe that an aerosol consists of a two-phase system
of particles and a surrounding gas. However, the Subcommittee
did not agree to include vapor phase acidity. Further research
will very likely show that "total available hydrogen ion per unit
volume of ambient air" is the entity that relates to adverse
biological effects. Until this research is done our
recommendation to list will possibly ignore a major fraction of
the potentially hazardous agent and thus may under-protect
exposed populations.
2) Next, the presently available human clinical
exposure studies are for short periods - usually less than two
hours. Because populations will be exposed for very prolonged
periods additional studies are desperately needed. Longer
exposures may show that effects increase upon longer exposure or
alternatively that effects disappear upon longer exposure. Such
studies are critical to defining whether peak levels of acidity
or some integrated measure of acid exposure should be listed.
Without this clarification substantial over-protection or under™
protection could result.
3) Finally, we do not presently have enough animal
toxicology data to identify the most sensitive sites in the body
with respect to acid injury. One must have such information in
order to project what human sub-populations are at greatest risk
and what the expected risks are.
4) Certainly the acid aerosol issue should not be
dropped. The available evidence indicates the real potential for
airborne acidity contributing to adverse effects in human
populations. However, until the above basic issues are better
understood it is difficult to envision the establishing of a
proper NAAQS,
5-2 Recommendation Not to List fDr. Georoe Wolff)
1) Health effects due to acid aerosols have been
demonstrated in controlled exposures but only at concentrations
which are much greater than an order of magnitude higher than
typical ambient levels. Even the highest concentration ever
reported in the ambient air is significantly lower than the
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lowest documented concentration ever associated with a
physiological response.
2) The assumption that the threshold dose for an
adverse health effect is 100 jug/m3-hr (i.e., 100 /ig/m3 x 1 hour =
10 pg/mj x 10 hours) is not supported by any of the data. In
fact, it is contrary to conventional wisdom because the body
produces ammonia which will neutralize a certain amount of the
acidity.
3) I question the accuracy of the ambient data,
particularly the extreme values, since there is no standard
procedure for measuring acid aerosols and the techniques used
have not been subjected to rigorous quality assurance protocols.
5.3 Majority Conclusions - Recommendation to List2
Based on its assessment of the technical and scientific
information presented in the Issue Paper, the Subcommittee
reached a nearly unanimous conclusion that the Clean Air
Scientific Advisory Committee should recommend that the
Administrator consider listing acid particles as a
criteria pollutant. In the Subcommittee's view* the cumulative
evidence provided by the available animal, controlled human
exposure, and epidemiologic studies clearly suggests possible
health effects associated with exposure t© acid particles.
The Subcommittee recognizes that the available data base is not
complete but is concerned by the potential health risks
resulting from exposures under typical ambient conditions.
The Subcommittee concluded that the weight of the evidence
from the disciplines of animal toxicology, controlled
clinical studies, and epidemiology is sufficient at this time
to recommend that the Administrator consider listing of acid
particles as a criteria pollutant.
In arriving at its recommendation* the Subcommittee took
into account that research currently underway should begin to
provide needed supplemental information in the next several
years. To further augment these ongoing efforts, the
Subcommittee has also identified key research needs that the
Agency should begin t© address immediately through a balanced and
adequately funded research program. These are discussed in the
separate report on acid aerosol research recommendations.
These nine members weres Dr. Mary Aradur, Dr. D©ug Dockery, Dr.
Robert Frank, Dr, Timothy Larson, Dr. Morton Lippmann, Dr.
Gilbert Omenn, Dr, Marc Schenker, Dr. Jerome Wesol©wski, and
Dr. Mark Utell.
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6.0 Literature Cited
Amdur, M.O.-and Chen, L.C. (1988) Furnace generated acid
aerosols; speciation and pulmonary effects. in:
International symposium on the health effects of acid
aerosols? addressing obstacles in an emerging data base,*
October 1987; Research Triangle Park, NC. EHP Environ.
Health Perspect.i In press.
Bauer et al., (1988) Am. Rev. Respir. Dis. 137:167.
Gearhart, J.M. and Schlesinger, R.B. (1988) Response of ^he
tracheobronchial mucociliary clearance system to repeated
irritant exposures effect of sulfuric acid mist on
structure and function. Exp. Lung Res.: In press.
Koenig, J.Q., Pierson, W.E., and Horike, M. (1983) The effects
of inhaled sulfuric acid on pulmonary function in adolescent
asthmatics. Am. Rev. Respir. Dis. 128i221-225.
Koenig, J.Q., Covert, D.S., and Pierson, W.E, (1988) The effects
of inhalation of acid compounds on pulmonary function in
allergic adolescent subjects. EHP Environ. Health
Perspect.s In press.
Spiezer, F,E. (1988) Studies of acid aerosols in six cities and
in a new multicity investigationi design issues. In:
International symposium on the health effects of acid
aerosols? addressing obstacles in an emerging data base.
October 1987; Research Triangle Park, NC. EHP Environ.
Health Perspect.s In press.
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APPENDIX A
Roster of the CASAC Acid Aerosol Subcommittee
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February 1933
U.S. Environmental Protection Agency
Science Advisory Board
Clean Air Scientific Advisory Committee
Acid Aerosol Subcommittee
Chairman
Dr. Mark Utell, Co-Director, Pulmonary Disease Onit, Professor of Medicine
and Toxicology, University of Rochester Medical Center, Box 692f
Rochester, NY 14642
Members
Dr. Mary Amdur, Senior Research Scientist, Energy Laboratorys MITS
Room 16-339, Cambridge, MA 02139
Dr. Doug Dockerys Harvard University, School of Public Health,
Department of Environmental Science and Physiology, 665 Huntington
Avenue, Boston, MA 02115
:t
Dr. Robert Frank, Professor of Environmental Health Sciences, Johns
Hopkins School of Hygiene and Public Health, 615 N. Wolfe Street,
Baltimore, MD 21205
Dr. Timothy Larson, Environmental Engineering aod Science Program,
Department of Civil Engineering FX-10, University of Washington,
Seattle, WA 98195
Dr. Morton Lippmann, Professor, Institute of Environmental Medicine,
NYU Medical Center, Tuxedo, NY 10987
Dr. Gilbert Omenn, Professor and Deans School of Public Health and
Community Medicine SC-30, University of Washington,
Seattle, WA 98195
Dr. Robert F. Phaleu, Community and Enviroonental Medicine, College of
Medicine, University of California-Irvine, Irvine, CA 92717
Dr. Marc Schenker, Director, Occupational and Environmental Health Unit,
University of California, Davis, CA 95616
Dr. Jerry Wesolowski, Mr and Industrial Hygiene Laboratory, California
Department of Health, 2151 Berkeley Way, Berkeley, CA 94704
Dr. George Wolff, Senior Staff Research Scientist, General Motors
Research Labs, Environmental Science Departaent, ¥arrens MI 48090
Execu t ive_Secretary
Mr. A. Robert FLaak, Environmental Scientist, Science Advisory Board
(A-lOlr), U.S. Environmental Protection Agency, Washington, D.C,
20460
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