April 14, 1998
EPA-SAB-IHEC-COM-98-001
The Honorable Carol Browner
Administrator
United States Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
Integrated Human Exposure Committee Commentary on Indoor
Air Strategy
Dear Ms. Browner:
This Commentary was developed by the Integrated Human Exposure Committee (IHEC)
of the Science Advisory Board (SAB) in response to a consultation on the draft Indoor Air
Strategy from the Office of Air and Radiation (OAR). The consultation took place at a public
meeting on July 22, 1997. The Integrated Human Exposure Committee has generated this
commentary in order to express its support of the Agency's efforts to address the cross-cutting
public health issues raised by pollutant exposures in indoor environments. This commentary
also includes recommendations for areas in which the Agency should expand its activities in
indoor air to increase the understanding of indoor air risks and risk reduction opportunities.
BACKGROUND
The indoor environment presents an important crosscutting issue for the Agency in its
mission to "protect public health and safeguard the natural environment." Since most of the
population spends about 90% of its time in indoor environments, exposures to most pollutants
occur indoors, whether from outdoor or indoor sources. Furthermore, many of the greatest
environmental health risks are encountered in indoor environments. Frequently, indoor levels of
many air pollutants are two to five times higher than corresponding outdoor levels. Pollutants
released outdoors can be brought into buildings with ventilation air. In some cases, the
chemicals that infiltrate into buildings undergo chemical reactions once indoors to generate
secondary pollutants. Pollutants released into the outdoor environment are also brought indoors
in food, water and tracked-in soil. Indoor pollution can also originate from indoor sources, such
as carpet, plywood, and other building materials. Examples of these consumer and commercial
products may include carpet, plywood, and other building materials. Indoor pollutants, such as
environmental tobacco smoke and household pesticides, may add to or potentiate the effects of
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outdoor pollutants. Thus, cost-effective reduction of risks from environmental pollutants
requires understanding total exposures (i.e., all sources, media, and exposure pathways) and the
relative contributions of both indoor and outdoor sources to total exposure and risk.
In 1990, in its report "Reducing Risk: Setting Priorities and Strategies for Environmental
Protection," the Science Advisory Board identified indoor pollution as a high risk deserving
EPA's attention (SAB, 1990). Subsequent and, in some cases, more quantitative relative risk
rankings by EPA Headquarters, regional offices and several states, have often identified indoor
pollution as being among the top four or five environmental risks to human health when
included in the list of risks to be ranked. Other scientific committees have also identified indoor
air as an important issue that needs further attention. For example, in March 1997, the
Presidential and Congressional Committee on Risk Assessment and Risk Management
highlighted indoor environmental issues as a problem that needs attention by Congress and the
Administration. Efforts to address human health issues in the indoor environment are widely
distributed across the EPA and other federal agencies. These efforts are often poorly integrated
because they cut across agency missions. Thus, the indoor environment presents a number of
challenges to EPA as well as the opportunity to be a national leader in addressing these issues.
CONCLUSIONS AND RECOMMENDATIONS
The Integrated Human Exposure Committee of the SAB strongly supports and
encourages efforts by the Agency to address the cross-cutting public health issues raised by
pollutant exposures in indoor environments through its Indoor Air Strategy, the Human Health
Indoors Policy Committee (HHTP), and its strategic goals for reducing environmental health
risks. The purpose of the HHTP Committee is "to develop an Agency-wide action plan to ensure
that EPA is prepared to meet the challenges of protecting human health indoors in the 21st
Century." The current efforts to set priorities and target reductions in the concentration of
selected indoor air pollutants are based on our limited analysis and understanding of indoor
health risks and risk reduction opportunities. However, there are many sources of indoor air
exposure data from government programs outside of the EPA that frequently do not reach the
peer-reviewed literature. One example is state, county and city health department programs that
routinely conduct environmental measurements as part of investigations of indoor air
complaints. IHEC recommends that the Indoor Air Strategy serve to facilitate communication
and coordination between the EPA and such programs. In addition, the IHEC recommends that
the EPA consider updating the last comprehensive assessment of the indoor environment which
was conducted by the National Research Council (NRC, 1981) over a decade ago. The Agency
should also consider broadening the indoor air assessment to include issues such as the
interaction and relative contributions of indoor and outdoor pollutants to total human exposure
and risk.
The Integrated Human Exposure Committee also recommends continued EPA efforts in
the measurement of indoor contaminant concentrations and exposures given their importance in
assessing risk. For example, the EPA Total Exposure Assessment Methodology (TEAM) studies
of volatile organic compounds in several U.S. cities, and the Particle (PTEAM) studies in
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California were important in characterizing the normal ranges of residential indoor and personal
air exposures for US populations and serve as the best available comparative, normative
reference (EPA, 1996; 1997). The Office of Radiation and Indoor Air's Indoor Environments
Division, through the Building Assessment Survey and Evaluation (BASE) study, has extended
the TEAM methodology to develop both measurement data on volatile organic compounds in
office buildings and related questionnaire data on health symptoms. This database provides a
major resource for advancing our understanding of exposures to these pollutants and "sick
building syndrome" in office workers.
Scientific understanding of indoor pollutants is still in its infancy when compared to
environmental science in outdoor environments. For example, several pollutants are not
currently detected during indoor air investigations due to the limitations of analytical techniques
that are routinely employed. There are multiple reasons that some indoor air pollutants are
"missed." Some compounds are missed because they are highly reactive (e.g., free radicals),
thermally labile, difficult to desorb from sampling media or chromatographic columns, or do not
produce an adequate response for the detectors that are used. Thus, there is a need for some
intermediate to long-term research to better understand the nature of indoor pollutants, their
sources and their dynamic behavior. The IHEC recommends that EPA's strategic planning
include plans for research to address these scientific gaps.
In addition to indoor air exposures, biomonitoring is an important tool for assessing risk.
The ability to measure indoor air pollutants or their metabolites in biologic tissues, in
conjunction with environmental air measurements, is an important next advancement in
characterizing the exposure chain. The biomonitoring activities under the third National Health
and Human Nutrition Examination Survey III (NHANES III) provided data that have already
strengthened the Agency's risk assessments, including some data that is specific to children's
risk. NHANES IV, which is being conducted by the National Center for Health Statistics with
partial funding from the EPA, will significantly increase this database. The National Human
Exposure Assessment Survey (NHEXAS) projects, which are managed by the Office of
Research and Development's National Center for Environmental Assessment, National Exposure
Research Laboratory, are examples of how to apply advancements in laboratory science to get
closer to understanding total, integrated exposure through all media and exposure routes (e.g.,
inhalation, ingestion, and dermal exposure). The IHEC strongly supports the EPA's efforts in
both the NHANES and the NHEXAS projects.
A more extensive analysis of opportunities for risk reduction, including risk associated
with exposure to indoor air contaminants, might also be undertaken as an Agency
implementation of the Integrated Environmental Decision Making Framework which the SAB is
just completing. The IHEC will be pleased to support the Agency in such an effort.
We trust that this Commentary will offer some insights on the importance of the Indoor
Air Strategy in expanding our understanding of indoor health risks and risk reduction options,
and on the opportunity for the EPA to further contribute to improving the scientific basis for
indoor air exposure and health risk assessment.
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Sincerely,
/signed/
Dr. Henry A. Anderson, Chair
Integrated Human Exposure Committee
/signed/
Dr. Joan M. Daisey, Chair
Executive Committee and Past Chair,
Integrated Human Exposure Committee
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REFERENCES CITED
EPA. 1987. The Total Exposure Assessment Methodology (TEAM) Study: Summary and
Analysis: Volume 1, USEPA Office of Research and Development, Washington, DC,
EPA/600/6-87/002a, June 1987.
EPA. 1996. The Particle TEAM, P TEAM Study: Analysis of the Data, Final Report, Volume 3,
USEPA Office of Research and Development, Washington, DC., EPA/600/R-95/098,
August 1996.
NRC. 1981. Indoor Pollutants, National Research Council, Washington, DC,
ISBN#030902770.
SAB. 1990. Reducing Risk: Setting Priorities and Strategies for Environmental Protection,
USEPA Science Advisory Board, Washington, DC, EPA-SAB-EC-90-021. September
1990.
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APPENDIX A - ACRONYMS AND ABBREVIATIONS
BASE - Building Assessment Survey and Evaluation
HHIP - Human Health Indoors Policy
NHANES - National Health and Human Nutrition Examination Survey
NHEXAS - National Health Exposure Assessment Survey
TEAM - Total Exposure Assessment Methodology
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U.S. ENVIRONMENTAL PROTECTION AGENCY
SCIENCE ADVISORY BOARD
INTEGRATED HUMAN EXPOSURE COMMITTEE
Chair
Dr. Joan M. Daisey, Indoor Environment Program, Lawrence Berkeley National Laboratory,
Berkeley, CA
Members
Dr. Paul Bailey, Mobil Business Resources Corporation, Product Stewardship & Toxicology,
Paulsboro, NJ
Dr. Henry A. Anderson, Wisconsin Bureau of Public Health, Madison, WI
Dr. Robert A. Harley, Department of Civil and Environmental Engineering, University of
California Berkeley, Berkeley, CA
Dr. Timothy Larson, Environmental Science and Engineering Program, Department of Civil
Engineering, University of Washington, Seattle, WA
Dr. Paul Lioy, Department of Environmental and Community Medicine, Robert Wood Johnson
School of Medicine, Piscataway, NJ
Dr. Kai-Shen Liu, California Department of Health Services, Berkeley, CA
Dr. Thomas E. McKone, School of Public Health, University of California, Berkeley, CA
Dr. Maria Morandi, University of Texas Health Science Center at Houston, School of Public
Health, Houston, TX
Dr. Jerome O. Nriagu, The University of Michigan, School of Public Health, Department of
Environmental and Industrial Health, Ann Arbor, MI
Dr. Barbara Petersen, Novigen Sciences, Inc., Washington, DC
Dr. Mark Utell, Pulmonary Disease Unit, University of Rochester Medical Center, Rochester,
NY
*Dr. Charles J. Weschler, Bell Communications Research, Red Bank, NJ
Mr. Ron White, American Lung Association, Washington, DC
Consultants
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Dr. Jonathan M. Samet, School of Hygiene and Public Health, The Johns Hopkins University,
Baltimore, MD
Science Advisory Board Staff
Ms. Roslyn Edson, Designated Federal Official, USEPA, Science Advisory Board, (1400), 401
M Street SW, Washington, DC 20460
Mr. Samuel Rondberg, Designated Federal Official, USEPA, Science Advisory Board, (1400),
401 M Street, SW, Washington, DC 20460
Mrs. Dorothy M. Clark, Staff Secretary, USEPA, Science Advisory Board, (1400), 401 M
Street, SW, Washington, DC 20460
* Dr. Weschler is a new Member who joined the Committee after the July meeting
but contributed to this commentary letter.
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NOTICE
This report has been written as part of the 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 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, nor of other agencies in the Executive Branch of the Federal government, nor does
mention of trade names or commercial products constitute a recommendation for use.
in
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