Written Statement
Statement
of Dr. Ronald E. Wyzga
EPRI
beforeto
the
SenateCommittee
on Environment and Public Works Committee
United
States Senate
October 2, 2002
I am Dr. Ronald E. Wyzga. I work for the Electric Power Research
Institute (EPRI), in Palo Alto, California.
EPRI, a voluntarily-funded 501(c ) (3) non-profit
organization operating in the public interest, is almost 30 years old and has
an annual budget of approximately $350 million. EPRI’s Environment Sector has an annual budget of approximately
$50 million; this makes EPRI one of the largest privately-funded health and environmental
research organizations in the world.
Within the Environment Sector, I am responsible for air quality
research, including research on the health effects of air pollution. The results of EPRI’s health and
environmental research is published and made publicly available, usually through
the peer-reviewed scientific literature.
I began my research career working
on the relationship between health and air pollution (specifically particulate matter) while a
graduate student at the Harvard School of Public Health, and my doctoral
dissertation in biostatistics in 1971 addressed this topic. Since then I have been actively engaged in
environmental health issues. I have
co-authored a book and published over 50 peer-reviewed papers. I have served on and chaired subcommittees
of the National Research Council (NRC), National Academy of Sciences. I currently serve on the NRC Committee on
Research Priorities for Airborne Particulate Matter. I have also served on or chaired several EPA Science Advisory
Board Committees, and I have been appointed a Fellow of the American
Statistical Association. The comments
that I present today reflect my personal views and judgments as a scientist who
has worked in this area for over thirty years.
These comments should not be construed to be the official opinion of my
employer or of any associate.
Summary
There are a large number
of scientific studies that report a link between air pollution and human
health. I have personally been involved
in some, and EPRI has supported many more.
The majority of these studies link particulate matter with health
effects; however, some of these studies do not show an association with health,
and other studies implicate gaseous pollutants in addition to, or in place of
particulate matter. In any consideration of the health and air pollution issue,
it is important to keep in mind that air pollution is a complex mixture of many
different types of gases and particles. Discerning specific causative agents is
a challenge we in the scientific community are working to address. Today I want to highlight some of the work
that EPRI has recently been involved in to provide you with some of our latest
results.
There have been several
major facets to our research:
1.)
It is important to
understand which specific components of air pollution are associated with
health impacts. In studies
undertaken to date, the strongest associations between air pollution and health
are with particulate matter. In
studies which include particulate matter (PM) and other pollutants, such as
ozone and carbon monoxide (CO), in their analyses, PM is most consistently
associated with health responses; there are, however, some exceptions where
other pollutants, especially carbon monoxide, are most highly associated with
health responses. Very few studies have considered a comprehensive set of the
pollutants, especially the different chemical constituents of particulate
matter, in their analyses. This is because monitoring
programs currently only measure a small number of compounds.
There
are limited data on the toxicity of the different components of particulate
matter. Few toxicology experiments have
been undertaken examining the different fractions of PM, but those that have
been done have found differences in toxicity for the different fractions. Other
results show that the total quantity of PM by weight does not explain
biological responses. Certain
components in PM appear to explain the toxicity of PM more readily than total
PM.
2.)
The EPRI ARIES
(Aerosol Research Inhalation Epidemiology Study) project was designed to
examine the toxicity of the various components of PM and air pollution. This study is unique in terms of the number
of air quality parameters measured and the number of health effects examined. This study, undertaken in Metropolitan Atlanta
in conjunction with several universities, US Department of Energy, and others,
characterized the air quality on a daily or more frequent basis for over one
hundred air quality variables. This
characterization, accompanied by a suite of epidemiological studies, allowed us
to examine the influence of the various components of air pollution on a
variety of health outcomes.
In general, the ARIES study is finding that different
components of air pollution are associated with respiratory effects than are
associated with cardiovascular effects (heart-related effects). More explanation of the preliminary results
is given in the detailed testimony, but in summary, the respiratory effects
appeared to be related to the gaseous pollutants (carbon monoxide, ozone, and
nitrogen dioxide) and cardiovascular effects were appeared to be associated
with PM-2.5 (particles 2.5 microns in size and smaller) and carbon
monoxide. However, the only
fraction of PM-2.5 that showed any association with the cardiovascular effects
were particles containing organic and elemental carbon. It is the
PM-2.5 PM2.5 fraction
that has been at the center of attention as the potential cause of negative
health impacts. For total mortality,
the pollutants most consistently associated with premature death are oxygenated
hydrocarbons, substances that to date have had limited study.
3.)
EPRI has initiated smaller ARIES-like studies in
Baltimore and St. Louis to determine whether the results from Atlanta can be
replicated elsewhere. A major effort is also
underway to launch a study very similar to ARIES in Chicago.
4.)
A major toxicology effort will start soon in which the
effects of coal combustion emissions will be investigated by exposing animals
to diluted, aged emissions from
power plants. This effort will provide important data to help
evaluate different combinations of fuel type, control technologies, and burning
configurations. The results of this
work will be particularly useful to help inform and complement the research
underway at the National Environmental Respiratory Center in Albuquerque, which
is also evaluating the toxicity of emissions from diesel and gasoline engines,
as well as wood smoke.
5.)
EPRI has also been active in trying to understand the
implications of alternative statistical methods used in the analyses of
epidemiological data. Given the
recent discovery that the applications of statistical software
have led to erroneous results in some pollution health studies, the EPA is
delaying its review of particulate matter health effects. Other statistical analyses require judgments
that can impact their outcome. It is
important to understand these potential impacts.
6.)
EPRI has undertaken studies to understand the
nature of exposure to the various constituents of air pollution, including
particulate matter and its major constituents.
We have found that there appears to be a better association between
personal exposure to particulate matter and outdoor measured levels than there
is for many of the gaseous pollutants.
What is particularly important is that recent results suggest that
there are short periods of time (in specific environments) when personal
exposures to pollutants are much higher (by factors of 5 for PM and over 50 for
carbonaceous particles) than the levels that we measure at our monitoring
stations. We also need to
establish whether these short-term peak exposures are related to health
responses.
7.)
Our joint study with Washington University of some
50,000 Veterans was designed to answer the question of whether there are
long-term (chronic) effects associated with air pollution. In this study we found that after
adjusting for many other factors Veterans who lived in cities with higher
levels of nitrogen dioxide and very high ozone levels died earlier
than those living in cleaner cities. We
could find no such effect, however, when we examined particulate matter.
There is a clear association
between air pollution and health in the US at pollution levels we have
experienced in the 1990s and earlier. Several different types of epidemiological
studies, undertaken at a wide variety of locations, have found associations
between air pollution and human health effects in the US. Among the various pollutants examined, the
strongest associations between air pollution and health are for particulate
matter (PM). Many of the earlier
studies (pre 1990s) considered just one or a limited number of pollutants; in
these studies, PM was frequently studied and found to be associated with health
effects. Later studies more frequently
examined multiple pollutants. Most of
these studies also found associations between PM and health effects, although a
subset of the studies found greater associations between health effects and
other pollutants, especially carbon monoxide (CO). In interpreting the results of these studies, several factors
must be taken into account. First, the
pollution measurements used in these studies were made at outdoor monitoring
sites; these are not necessarily representative of personal exposures to these pollutants pollutants.
We now have some limited data on the differences between personal
exposures and outdoor measurements. These differences are not the same for
every pollutant measured, leading to possible statistical impacts on the
results of the analyses of the relationships between air pollution and health.
Second, studies can only consider pollutants for
which measurement data are available, and only a few pollutants/substances are
generally measured. If the pollutant(s)
that are truly responsible for health effects are not measured, then other
pollutants that are measured and present at the same time as the responsible
pollutants can be associated statistically with health effects. In such cases
what we measure and use in our analyses could be a surrogate for something that
is not measured. In all of our study results we need to keep this in mind. The only way to overcome this issue is to
measure as many components of air pollution as possible, hopefully including
the true culprit (or culprits), which only
detailed analyses can reveal.
There is as yet no accepted
biological explanation for the link between the levels of pollution found in
the US today and observed health responses. Past research has focused on epidemiological
studies—observational studies on humans going about their normal activities. . Laboratory research, which has been limited to date,
can focus on establishing the underlying biological mechanisms that can cause
negative health effects. Several
possible biological explanations have been put forth to explain the results
from epidemiological studies, and recent laboratory results support some of
these hypotheses. For example, one study appeared to show that blood clotting
can increase with exposure to higher levels of fine particulates. If this
occurs, it could be an explanation for why some heart disease effects are
related to fine particulate levels in epidemiological studies. At
this time, I believe that the most likely scenario is that a combination of
explanations is responsible for the effects observed, with different mechanisms
acting for different air pollution/PM components. Different mechanisms may also be acting in susceptible
individuals, such as asthmatics or those with hypertension. Clearly, much more work is needed to gain
insight into the mechanism(s) of PM action.
Particulate matter is a complex
mixture and its composition varies over time and place. Some of
these major components (e.g., organic matter) contain hundreds of chemical
compounds. The most important fractions
of PM are carbon-containing particles and sulfate in the Eastern US, with
carbon-containing particles being more important in urban areas. In the Western US, nitrates are more
important and sulfates are generally less important.
There are limited data on the
toxicity of the different components of particulate matter. Several
PM components have been hypothesized to play a role in toxic responses,
including acid aerosols, metals, sulfates, nitrates, ultrafine particles (very
tiny particles much smaller than the PM-2.5 particles), bioaerosols (including
pollen and mold spores), diesel exhaust particles, and organic compounds. Toxicological and human exposure evidence suggests that acid
aerosols do not contribute much to the adverse respiratory outcomes
observed in epidemiological studies; however, acid components have not been
assessed thoroughly with respect to potential cardiovascular effects. Metals have been shown in multiple
studies to cause cell injury and other effects. . Particle size, specifically the ultrafine fraction,
may also be important in the development of health effects. A number of studies have investigated the
effects of ultrafine particles and have found lung inflammation and other
respiratory effects, although it appears that chemical composition may play a
key role in the responses observed.
Cardiovascular and systemic effects of ultrafine particles have been
investigated to only a limited extent. Bioaerosols
are not considered to account for the reported health effects of ambient PM as
their concentrations are very low and health effects can occur at times when
bioaerosol concentrations are low. Toxicological evidence is
accumulating to suggest that diesel PM can exacerbate the allergic
response to inhaled allergenic material.
Finally, the organic compounds associated with PM have been little-studied from a toxicological perspective, although they represent a substantial portion of the mass of ambient PM (10-60% of total dry mass). Other fractions of PM, including sulfates and nitrates, appear to be of less concern.
In a recent draft report, the
Netherlands Aerosol Programme concluded:
“Based upon current toxicological and human clinical knowledge: water,
sea salt, ammonium sulfate, ammonium nitrate, and probably non-crystalline
crustal material too, can be considered an inert part of PM-10 at the ambient
concentrations in the Netherlands.”
This report has not yet been finalized, and the conclusions are still
under discussion.
In order to more fully understand
which components of PM are responsible for the health effects observed,
additional toxicological studies must be conducted. Studies, which examine the toxicity of
emissions from various sources of pollution, can be informative
in identifying those pollutants (and sources) most highly associated with
health responseseffects.
The EPRI ARIES study was
designed to examine the toxicity of the various components of PM and air
pollution. This study is unique in terms of the number of air quality
constituents measured and the number of health effects examined. The best way to increase our understanding of
the types of PM and air pollution that may be responsible for the health
effects observed in other studies is to undertake a study in which all of the
potentially relevant fractions of PM are measured. . Traditionally we only measure what is required because of
local, state or federal regulations. On occasion a research study may measure a
larger array of air pollutants, but it is rare to have a large number of
constituents measured systematically over an extended period of time. ARIES addresses this need through detailed
air quality characterization for a period of over two2 years and
through undertaking several epidemiological studies to relate air quality
characteristics to health effects.
Appendix A provides further details about ARIES, as well as provisional
results..
Extensive daily - and in some cases
continuous - measurements were made for all of the particle size fractions and
constituents about which concerns have been raised. At the same time, several epidemiological studies were
undertaken to examine the potential health effects of the various constituents.
Initial results from the analytical team focused upon the subset
of air pollution measures tied to the major existing hypotheses about the
pollution/ health
relationship. Results based upon the first year’s data have been published in
peer-reviewed journals; two years of data have now been analyzed and manuscripts
based upon analyses of 2 two years worth of data are now under
preparation for peer review. The draft
results are very informative, and I would like to share them with you.
These results are complex and
reflect a methodology that examined pollutants individually. Analyses which consider several pollutants
simultaneously are planned and may help identify the pollution components that
are of greatest concern.
· Several
pollutants are statistically significantly associated with daily mortality
of those over 65 years old; they include PM-2.5, PM-10, CO (carbon monoxide),
and oxygenated hydrocarbons. When
alternative statistical models were applied, the results were most consistent for
oxygenated hydrocarbons, a measure pollutant that has not previously been
considered in air pollution health studies.
Results are available for several morbidity (disease) measures
including emergency room admissions to Atlanta area hospitals, unscheduled
physician visits to a health maintenance organization (HMO), and responses of
defibrillator devices implanted in patients with erratic heart rhythms. Preliminary analyses of heart rate
variability considered only PM-2.5 and not its components nor gases. Based on
these limited data, PM-2.5 was found to be associated with
statistically-significant changes in heart rate variabilitys.
·
Lung and respiratory problems were
related to PM-10 and to pollutant gases including ozone, nitrogen dioxide, and
carbon monoxide.
·
· Heart
disease responses were much more likely to be related to PM-2.5, carbon
monoxide, and nitrogen dioxide.
· Organic
compounds were associated with several cardiovascular effects.
· When
the components of PM-2.5 were considered, the only ones found to be significant
were elemental and organic carbon.
· There
was little evidence of any health effects tied to acid aerosols.
·
No associations were found between any health effect
and total soluble metals; additional analyses are planned to look at
individual metals.
· No
associations were found with ultrafine particles. . Since the
concentrations of these particles appear to change so rapidly over time and
space, it is doubtful that the ARIES study could shed much light on the effects
of these particles. Nevertheless, their
concentrations are unrelated to the concentrations of other particle fractions;
hence it is unlikely that ultrafine particles can explain the association seen
with other particles.
· No cardiovascular or respiratory effects were associated with sulfates.
ARIES did not look at sources of
pollution directly. We did, however,
undertake a source-attribution analysis of the organic compounds in
Atlanta. Cardiovascular effects were
found in the winter months only in this study.
In the winter months, organic compound concentrations were tied
principally to wood smoke, although diesel emissions were also a
contributor. Diesel emissions were also
a major contributor to organic compounds in the summer months when no
cardiovascular effects were related to these compounds.
There is a great need for additional studies which focus upon the specific components of particulate matter and examine their relationship to human health. The ARIES study will provide an important piece of evidence in understanding which fractions of PM and of air pollution are the most important in affecting human health. ARIES results are from one metropolitan area, Atlanta. Atlanta is a logical place for a study; it has high pollution levels, many sources of pollution, and no unique sources of pollution that would yield a unique result. Nevertheless it is important to undertake similar studies in other metropolitan areas. We are now engaged in similar, although more limited, studies in St. Louis and Baltimore, where detailed monitoring is underway. Much of this monitoring is funded by EPA’s supersites monitoring program. Undertaking such studies is expensive because the air quality monitoring itself is costly; hence, governmental resources to undertake such studies are critical.
Secondly, more laboratory studies are needed
which examine specific fractions of particulate matter and its toxicity. Since it would be very costly and time-consuming to test all
specific compounds rigorously in laboratories, special protocols should be
considered which examine the mixture of pollutants associated with specific
sources. For example, studies are now
underway at the National Environmental Respiratory Center to examineing the toxicity
of emissions from several sources. EPRI
is planning some similar efforts, but clearly more research is needed. There are a large variety of emissions from
different sources, and we need to learn how these emissions interact with other
pollution elements once they enter the environment at large.
An ongoing committee of the
National Research Council, of which I am a member, will issue a report next year identifying the highest priority
research needs to inform particulate matter-health policy issues.
The implications of the
statistical methods used to investigate the relationship between health and air
pollution need to be fully understood. A recent announcement by
researchers at Johns Hopkins University raised some issues about the the past
use of one particular statistical approach and its related software. . Fortuitously, at a meeting
of EPRI researchers with our advisors, it was decided to use alternative
statistical methods in our research, and we have examined these methods
thoroughly. We have found that, on occasion, ARIES
results, especially in the mortality analyses, can be influenced by changes in
the statistical approach even when the alternative approaches are judged
reasonable by statisticians. For
example, carbon monoxide (CO) was found to be statistically significantly
associated with daily deaths of those over 65 years
old with one approach but not with the other.
Fortunately most results were similar across the various approaches, but but because there are
some differences. , iIt is important
to articulate and understand these differences.
1.
Air pollution likely impacts the health of individuals
in the US today.
2.
Particulate matter is a likely candidate to explain
these impacts.
3.
Not all fractions of particulate matter appear to be
equally toxic.
4.
When health effects are associated with fine particles,
our research points strongly to carbon-containing particles that
contain carbon as the agents of concern; in most US cities,
carbon-containing particles are also the largest particle component by weight.
5.
Gaseous pollutants are still of concern and cannot be
ignored.
6.
There is a strong need to identify with more certainty
those specific components of air pollution which cause health effects.
7.
We need to understand in more detail the personal
exposure of susceptible individuals to the various air pollution
components. In particular, we need to
identify when and where peak exposures occur and whether these peaks are
important to health.
8.
There is a great need to apply alternative statistical
methods in analyzing data and to understand the influence of a specific method.
1.
Decreasing the non-toxic part of
particulate matter will not reduce health risks.
9.