Exposure Analysis

510 Pages·2006·19.742 MB·English

by  Wayne R. Ott, Anne C. Steinemann, Lance A. Wallace

EXPOSURE
ANALYSIS
Edited by
Wayne R. Ott
Anne C. Steinemann
Lance A. Wallac e
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Library of Congress Cataloging-in-Publication Data
Exposure analysis / edited by Wayne R. Ott, Anne C. Steinemann, Lance A. Wallace.
p. cm.
Includes bibliographical references and index.
ISBN 1-56670-663-7 (alk. paper)
1. Biological monitoring. 2. Environmental monitoring. I. Ott, Wayne. II. Steinemann, Anne C. III.
Wallace, Lance A.
RA1223.B54E97 2006
615.9’02--dc22 2006043890
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Foreword
Our greatest progress in improving public health has occurred in those environmental regulatory
programs most closely based on accurate measurements of human exposure. Probably no single
topic in the environmental sciences is more important than exposure analysis. Yet exposure science
has not always received the attention warranted. Knowing quantitatively what people are exposed
to, by how much, when, and where it comes from is the centerpiece of exposure analysis. Only by
accurately determining the sources of exposure can we protect public health by reducing exposure.
As measurements of population body burden continue to show elevated concentrations of many
toxic pollutants in humans, reasonable questions will be asked about the sources of these pollutants.
Exposure analysis provides the basic tools and methods needed to identify the sources, understand
the causes, alter the exposures, and track the changes over time. This book is dedicated to the
development of exposure analysis as a new scientific field in its own right. That is, exposure analysis
is not just a collection of related interdisciplinary approaches; it is a field unto itself. This book
takes an important first step by identifying the building blocks of this new field.
© 2007 by Taylor & Francis Group, LLC
Preface
Exposure analysis is at the heart of methods to protect public health from the harmful effects of
pollution. Though not well developed when early environmental laws that affect exposure were
written, exposure analysis has become a rapidly growing science. Perhaps the most important
contribution of programs dealing with environmental pollution has been the initiation and devel-
opment of this new field of exposure analysis as a formal science.
This book introduces the reader to the science of exposure analysis. It is assumed that the
reader has at least a college-level understanding of mathematics and chemistry but may not be
familiar with the methods of exposure analysis. Due to the breadth of exposure science as a field,
this book is intended for a wide audience, including environmental engineers, public health officials,
environmental scientists, risk assessors, indoor air quality specialists, government regulators, and
members of the public interested in environmental science. The book is also relevant to disciplines
concerned with occupational health, industrial hygiene, toxicology, epidemiology, statistics and
biostatistics, and environmental engineering.
When Stanford University began teaching its Introduction to Human Exposure Analysis course
in the Department of Civil and Environmental Engineering, no classroom textbook was available.
To help fill this need, a course reader on exposure analysis was developed. This new course was
open to graduate and undergraduate students of all disciplines, and it included a laboratory com-
ponent in which students form small groups and carry out experimental laboratory studies using
state-of-the-art exposure monitors. After a decade of teaching this course, the authors of many of
the scientific papers used in the course were invited to contribute chapters to this book. Every year
the students provided written comments on the chapters, and the student feedback was used to
revise the chapters and improve their clarity.
Planning a textbook requires decisions about its level and content — whether to organize the
book by pollutant groups, such as dioxin and pesticides, or by general methods, such as measure-
ment techniques. This book combines the two approaches, building most of the chapters upon the
individual pollutants and pollutant classes, which are grouped by air, dermal, ingestion, and mul-
timedia routes of exposure. The book’s structure is outlined briefly below.
Chapter 1, Exposure Analysis: A Receptor-Oriented Science, introduces an important principle
of exposure analysis: it often begins by measuring exposure — what people actually breathe, eat,
drink, or have skin contact with — and then moves backward to find the true sources of that
exposure. Thus, it follows a receptor-to-source (receptor-oriented) approach as well as the more
traditional source-to-receptor (source-oriented) approach. The receptor-oriented approach has dem-
onstrated its effectiveness by discovering many new sources of exposure that previously were
overlooked but are important for protecting public health. The receptor-oriented approach is not
unique to exposure analysis; it also is a fundamental part of the forensic process of criminal
investigations, as illustrated by Agatha Christie’s Monsieur Hercules Poirot, who discovers a body
and then works backward to find the causes (persons responsible) for the death.
Chapter 2, Basic Concepts and Definitions of Exposure and Dose, summarizes the existing
definitions of exposure, dose, and related concepts. It also provides a mathematical framework that
is at the heart of these conceptual definitions. The glossary included at the end of Chapter 2 presents
definitions of common terms used in the field, which are consistent with the definitions adopted
by the International Society of Exposure Analysis (ISEA) and other international groups.
Chapter 3, Probability-Based Sampling for Human Exposure Assessment Studies, discusses
the statistical methods used in human exposure measurement field studies. The science of exposure
© 2007 by Taylor & Francis Group, LLC
analysis has made a major contribution to the older science of environmental monitoring by
conducting large-scale population exposure field studies that have clearly stated objectives, good
statistical protocols, and well-planned probability sampling designs.
Chapter 4, Inhalation Exposure, Uptake, and Dose, introduces a collection of chapters on human
exposure through the air carrier medium (Chapter 4 through Chapter 10). Chapter 4 reviews the
physical and physiological processes affecting the movement of pollutants in air and their transfer
to the human respiratory system.
Chapter 5, Personal Monitors, describes small, portable devices that people can wear or carry
with them to measure their exposure to air pollutants. Many personal monitors are real-time
instruments that can measure and record data on a minute-by-minute basis. Other types (active
samplers) use a small pump that the person wears along with a collection filter, while still others
(passive samplers) have no pump but rely on diffusion to collect a sample.
Chapter 6, Exposure to Carbon Monoxide (CO), shows that ambient concentrations and personal
exposures to CO have greatly decreased in the United States over several decades due to effective
regulatory programs. Exposure to this pollutant is still widespread in other parts of the world,
however. One important component of this successful environmental program has been the avail-
ability of excellent CO measurement methods for ambient, indoor, and personal exposures. The
full story of exposure to CO and the scientific history of its decrease in the United States provide
an important lesson in exposure analysis, because CO has been explored so thoroughly from an
exposure standpoint.
Measurement studies using personal monitors have shown that Exposure to Volatile Organic
Compounds (VOCs) (Chapter 7) is both significant and widespread. This class of thousands of
pollutants is present in countless consumer products and building materials, providing typically
two to five times as much exposure as the major outdoor sources of “air toxics” that are subject
to ambient regulation. The more important indoor sources are largely unregulated. Exposure studies
were able to pinpoint many of these sources, providing findings that may allow persons to reduce
their exposure by removing sources from the home, changing their buying habits, or carrying out
other lifestyle changes. However, it is important to convey the findings from these studies to the
general public.
Chapter 8, Exposure to Particles, points out that the World Health Organization estimates that
1.6 million deaths a year are due to indoor air pollution, mostly in developing countries, from
particles created from combustion during cooking and heating. An unanswered question is the
relative influence of indoor and outdoor sources on exposure, and new ways to separate the
contributions of indoor and outdoor sources to particle exposure are explained.
Chapter 9, Exposure to Secondhand Smoke, illustrates the effectiveness of exposure analysis
studies in changing human behavior and improving public health. Although many cities, counties,
states, and nations have acted to ban smoking in public places, these bans would not have occurred
without the scientific measurements of concentrations in the locations where smokers and other
people congregate.
Chapter 10, Intake Fraction, compares the relationship of sources to exposures when people
are in indoor vs. outdoor locations. It shows that a pollutant released in a residence has odds of
being inhaled that are typically 1000 times the odds of inhaling the same pollutant if released
outdoors. The high efficiency of small indoor sources literally under our noses helps explain why
studies find indoor pollutant concentrations are often very high.
Chapter 11, Dermal Exposure, Uptake, and Dose, introduces the reader to the emerging science
of the dermal route of exposure and dose to toxic agents. It describes the factors affecting absorption
by the human skin, the mechanisms of exposure, techniques for directly measuring dermal exposure,
and techniques for measuring absorption. It includes a glossary of terms on dermal exposure that
may be unfamiliar to some readers, especially biological terms about the human skin.
Chapter 12, Dermal Exposure to VOCs while Bathing, Showering, or Swimming, deals with
an important aspect of dermal exposure — the absorption of volatile organic compounds while
© 2007 by Taylor & Francis Group, LLC
showering or bathing. It discusses the first set of experiments that were able to measure directly
the dermal uptake of chloroform (a by-product of water treatment) while bathing.
As noted in Chapter 13, Ingestion Exposure, the gut (gastrointestinal system) is one of our
three major barriers to absorbing environmental pollutants (the others being the lung and the skin).
Calculating intake requires knowledge of the amount and kinds of food eaten or liquids drunk,
gained from activity pattern studies, Market Basket surveys, USDA statistics, and similar sources.
Also required is knowledge of the absorption, metabolism, and excretion of organic and inorganic
substances.
Chapters 14 through 17 deal with exposure through multiple carrier media. Many pollutants,
such as lead and polycyclic aromatic hydrocarbons, reach people through more than one carrier
medium, such as air breathed and food eaten, and therefore they come under the category of
multimedia exposure.
Chapter 14, Exposure to Pollutants from House Dust, summarizes studies on the concentrations
of pollutants measured in the house dust of American homes. Adults and children can be exposed
to pollutants in house dust by resuspension in the air, hand-to-mouth contact, ingestion, and skin
contact. Pollutants in house dust often exceed the levels that would trigger a risk assessment at a
Superfund site, and the causes of these elevated concentrations usually are common everyday
sources, such as house paint in older homes. Effective vacuuming is one way to reduce the exposure
of adults and children in homes, although efficient vacuuming requires an agitator brush and an
embedded dirt finder.
Chapter 15 provides an overview of exposure to pesticides, including the use of personal
monitors in pesticides exposure monitoring field studies and the findings from these studies.
Although many pesticides reach people through the food they eat, air is the dominant carrier medium
for exposure to many pesticides, especially indoor air.
Chapter 16 describes exposure to dioxin and dioxin-like compounds, which are multimedia
pollutants that reach humans primarily through the food carrier medium. Although widespread in
the environment, human exposure to dioxins in the United States has exhibited a decreasing trend
over time.
Biomarkers of Exposure (Chapter 17) deals with measurements of pollutants in the body,
particularly in blood, urine, and exhaled breath. A great advantage of biomarkers is that they can
show immediately which pollutants are most important in terms of entering the human body. For
example, two nationwide studies, one using biomarkers in exhaled breath and the other in blood,
agreed in identifying a small number of about a dozen volatile organic chemicals (out of the
thousands present in the environment) as the most prevalent in our bodies. Comparing body burden
to measured levels of exposure can identify previously unsuspected routes of exposure—an example
described in the chapter is the discovery that smokers receive close to 90% of their benzene
exposures from mainstream cigarette smoke.
In addition to progress in measuring the chemical and physical properties of pollutants reaching
people, there has been progress in the development of mathematical models to estimate and predict
exposures. Because of the importance of indoor air quality in estimating human exposure to air
pollutants, Chapter 18, Mathematical Modeling of Indoor Air Quality, describes quantitative meth-
ods that have been validated for predicting the concentrations in enclosed everyday locations, such
as automobiles and rooms of the home. Modeling Human Exposure to Air Pollution (Chapter 19)
describes quantitative techniques for predicting personal exposure to air pollution, and Models of
Exposure to Pesticides (Chapter 20) reviews an emerging area of exposure modeling.
Finally, because of the policy implications of many of the scientific exposure studies, Chapter
21, Environmental Laws and Exposure Analysis, reviews how federal laws in the United States
deal with human exposure to environmental pollution. The laws generally focus on large outdoor
sources while underemphasizing smaller indoor sources of the same pollutants that cause greater
exposure. Human exposure studies reveal that most of our exposure to toxic pollutants comes from
© 2007 by Taylor & Francis Group, LLC
common everyday sources that are close to us and are often overlooked, such as consumer products
and building materials.
Accurate measurements of exposure are some of the most promising ways to help guide our
environmental programs to protect and improve pubic health. These measurements allow us to
focus more precisely than ever before on traditional sources as well as on important sources found
close at hand in our homes and that are often overlooked, such as cleaning supplies, air fresheners,
fragrances, paints, adhesives, chlorinated water, interior furnishings, attached garages, particle
board, house dust, molds, pesticides, secondhand smoke, cooking activity, fireplaces, candles,
incense, and the multitude of products we use daily in our lives. Great strides have been made in
improving the science of exposure analysis, and its relevance for protecting health is so far reaching
that it is hoped that exposure science will receive greater emphasis in future policies and laws.
Many of the authors of this book have made fundamental pioneering contributions to the field
of exposure analysis. As editors and readers, we are fortunate to have their contributions to this
textbook. We believe the chapters in this book are authoritative reviews and will be helpful to
readers for a considerable length of time.
© 2007 by Taylor & Francis Group, LLC
About the Editors
Wayne R. Ott has worked on developing new methods to measure, quantify, and predict human
exposure to environmental pollutants for 4 decades. His Ph.D. research at Stanford University
included a large-scale personal exposure monitoring field survey. He was an environmental engineer
in the Commissioned Corps of the U.S. Public Health Service assigned to the USEPA’s Office of
Research and Development for 30 years. As team leader of USEPA’s Air, Toxics, and Radiation
Monitoring Research Staff, he coordinated scientific research on measurement methods, nationwide
monitoring networks, exposure modeling, and human exposure field surveys. He received the 1995
Jerome J. Weselowski award for his contributions to the knowledge and practice of exposure analysis
and the Public Health Service Commendation Medal for developing a nationally uniform air
pollution index. Since coming to Stanford from USEPA in 1996, he has continued working on
methods to measure and predict human exposure for a variety of common everyday sources, such
as cigarettes, cigars, pipes, cooking, candles, incense, motor vehicles, and wood smoke. He con-
ducted field measurements of exposure to secondhand smoke in California taverns, restaurants,
gaming casinos, homes, and automobiles and has authored or co-authored over 100 journal articles,
conference presentations, and research reports, including the CRC Press book, Environmental
Statistics and Data Analysis. He is consulting professor, civil and environmental engineering,
Stanford University, and visiting scholar at the department of statistics.
Anne C. Steinemann is Professor of Civil and Environmental Engineering, Professor of Public
Affairs, and Director of The Water Center at the University of Washington. She received her Ph.D.
in Civil and Environmental Engineering from Stanford University. Dr. Steinemann specializes in
environmental impact assessment and regulatory policy, water resources management, hazard
prediction and mitigation, and health effects of pollutants, combining expertise in engineering,
economics, policy, and public health. She received the National Science Foundation CAREER
Award in addition to university and national teaching awards. Dr. Steinemann has investigated more
than 100 sick buildings to identify pollutant sources, reduce exposures, and improve occupants’
health. She conducted the first national epidemiological study of chemical sensitivity, its causes
and symptoms related to exposures, and its overlaps with asthma. Dr. Steinemann has directed
more than $5 million of funded research, and serves as adviser to agencies and industries on
environmental issues. Among her recent publications is the textbook, Microeconomics for Public
Decisions (South-Western, 2005).
Lance Wallace has concentrated throughout his career on developing methods such as personal
air quality monitors and breath analysis to measure human exposure to air pollution. Dr. Wallace,
whose Ph.D. is in physics, conceived and implemented the USEPA TEAM studies of human
exposure. These very large-scale studies used personal monitors carried by more than 2000 persons
(selected to represent more than 2 million residents of a number of U.S. cities) to measure their
exposure to volatile organic compounds, pesticides, carbon monoxide, and respirable particles.
Many new unexpected sources of these pollutants were found, leading to an increased emphasis
on personal behavior, consumer products, and building materials as sources of exposure. Dr. Wallace
received a number of awards from the USEPA for these and other studies carried out during his
30-year career with the agency. He spent 2 years as a visiting scholar at Harvard University and
has served as an advisor to a number of doctoral students at Harvard, Johns Hopkins, and the
University of Washington. He has published 80 articles in peer-reviewed journals, one book and
© 2007 by Taylor & Francis Group, LLC
15 book chapters, and more than 100 research reports and presentations at conferences. Dr. Wallace
received the Jerome J. Weselowski award for lifetime contributions to human exposure and the
Constance Mehlman award for scientific contributions affecting environmental policy from the
International Society for Exposure Analysis (ISEA).
© 2007 by Taylor & Francis Group, LLC
Acknowledgments
Grateful appreciation is given to the members of the Advisory Board of this book for providing
thoughtful suggestions in the initial planning stages. The Advisory Board members were Prof.
Richard L. Corsi (Department of Civil Engineering, University of Texas at Austin), Prof. Naihua
Duan (University of California at Los Angeles), Prof. Peter G. Flachsbart (Department of Urban
and Regional Planning, University of Hawaii at Manoa), Prof. Petros Koutrakis (Harvard School
of Public Health, Harvard University), Profs. James Leckie and Lynn Hildemann (Department of
Civil and Environmental Engineering, Stanford University), Prof. P. Barry Ryan (Rollins School
of Public Health, and Department of Chemistry, Emory University), and Prof. Kirk R. Smith
(University of California at Berkeley).
Grateful appreciation also is given to Rashida Basrai, Sabiha Basrai, Bayard Colyear, Karen
Johnson, and Willa AuYeung for their contributions to the graphics and artwork of this book, to
Dan Ribeiro and Deborah Livingstone for their editing of the chapters, and to Paloma Beamer for
providing thoughtful comments and student input on the chapters.
Special appreciation is given to Prof. James Leckie for his contributions to dermal exposure
science and for developing a pioneering course on the Introduction to Human Exposure Analysis
at Stanford’s Department of Civil and Environmental Engineering and to Valerie Zartarian, Robert
Canales, Alesia Ferguson, Kelly Naylor, Andrea Ferro, Paloma Beamer, and Timothy Julian for
teaching this new course.
© 2007 by Taylor & Francis Group, LLC