U.S. Senate Committee on Environment & Public Works
U.S. Senate Committee on Environment & Public Works
Hearing Statements
Date:   04/01/2004
Statement of George D. Thurston, Sc.D.,
New York University School of Medicine
Division: Environmental Medicine
Implementation of NAAQS on PM2.5

Mister Chairman and members of the Subcommittee, I am George D. Thurston, a tenured Associate Professor of Environmental Medicine at the New York University (NYU) School of Medicine. My scientific research involves investigations of the human health effects of air pollution.

I am also the Director of the National Institute of Environmental Health Sciences' (NIEHS) Community Outreach and Education Program at NYU. A goal of this program is to provide an impartial scientific resource on environmental health issues to decision-makers, and that is my purpose in testifying to you here today.

The adverse health consequences of breathing ozone or particulate matter are serious and well documented. This documentation includes impacts demonstrated by controlled chamber exposures and by observational epidemiology showing consistent associations between these pollutants and adverse impacts across a wide range of human health outcomes. The implementation of the NAAQS promulgated by the U.S. EPA on July 18, 1997 will provide a substantial improvement in the public health protection provided to the American people by the Clean Air Act.

Ozone (O3) is a highly irritating gas which is formed in our atmosphere in the presence of sunlight from other "precursor" air pollutants, including nitrogen oxides and hydrocarbons. These precursor pollutants, which cause the formation of ozone, are emitted by pollution sources including automobiles, electric power plants, and industry.

Particulate Matter (PM) air pollution is composed of two major components: primary particles, or "soot", emitted directly into the atmosphere by pollution sources such as industry, electric power plants, diesel buses, and automobiles, and; "secondary particles" formed in the atmosphere from sulfur dioxide (SO2) and nitrogen oxide (NOx) gases, emitted by many combustion sources, including coal-burning electric power plants.

Observational epidemiology studies have shown compelling and consistent evidence of adverse effects by ozone and PM. These studies statistically evaluate changes in the incidence of adverse health effects in a single population as it undergoes varying real-life exposures to pollution over time, or across multiple populations experiencing different exposures from one place to another. They are of two types: 1) population-based studies, in which aggregated counts of effects (e.g., hospital admissions counts) from an entire city might be considered in the analysis; and, 2) cohort studies, in which selected individuals, such as a group of asthmatics, are considered. Both of these types of epidemiologic studies have confirmed the associations of ozone and PM air pollution exposures with increased adverse health impacts, including:

- decreased lung function (a measure of our ability to breathe freely);

- more frequent respiratory symptoms;

- increased numbers of asthma attacks;

- more frequent emergency department visits;

- additional hospital admissions, and;

- increased numbers of daily deaths.

Among those people known to be most affected by the adverse health implications of air pollution are: infants, children, those with pre-existing respiratory diseases (such as asthma and emphysema), older adults, and healthy individuals exercising or working outdoors. The state of the science on particulate matter and health has undergone thorough review, as reflected in the in the recently released draft of the U.S. EPA Criteria Document for Particulate Matter-of which I am a contributing author. Since the PM2.5 standard was set in 1997, the hundreds of new published studies, taken together, robustly confirm the relationship between PM2.5 pollution and severe adverse human health effects. In addition, the new research has eliminated many of the concerns that were raised in the past regarding the causality of the PM-health effects relationship, and has provided plausible biological mechanisms for the serious impacts associated with PM exposure.

In my own research, I have found that both ozone and particulate matter air pollution are associated with increased numbers of respiratory hospital admissions in New York City, Buffalo, NY, and Toronto, Ontario, even at levels below the current standards. My results have been confirmed by other researchers considering locales elsewhere in the world (e.g., see Schwartz, 1997). Indeed, the U.S. EPA used my New York City asthma and air pollution study results in their "Staff Paper" when setting the ozone air quality standard in 1997. Furthermore, I was Principal Investigator of an NIH funded research grant that showed in an article published in the Journal of the American Medical Association (JAMA) that long-term exposure to particulate matter air pollution is associated with an increased risk of death from cardio-pulmonary disease and lung cancer, as displayed in Figure 1 (Pope et al, 2002). In fact, the increased risk of lung cancer from air pollution in polluted U.S. cities was found in this study to be comparable to the lung cancer risk to a non-smoker from living with a smoker. Thus, the health benefits to the U.S. public of meeting these new air quality standards by reducing ozone and particulate matter will be substantial.

Figure 1. Lower PM2.5 Levels Are Associated with Lower Mortality

Source: Pope, Burnett, Thun, Calle, Krewski, Ito , and Thurston. (Journal of the American Medical Association, JAMA, 2002)

But air pollution affects a much broader spectrum of human health than mortality. In 1997, in order to give the Congress some insight into the large numbers of adverse health effects that could be avoided by meeting the new air quality standards, I made working estimates of some of the other documented adverse health impacts of ozone exposure that will also be reduced in New York City when the proposed new ozone standard is fully implemented. The results of my analysis, which were included in the Senate hearing records at the time, are presented in Figure 1 below, entitled the "Pyramid of Annual New York City Adverse Impacts of Ozone Avoided by the Implementation of the Proposed New Standard".

Figure 2. Pyramid of Adverse Effects Associated with Meeting the Ozone Standard in New York City (G. Thurston, 1997).

While there are about 7 million persons in New York City, there many more millions of persons throughout the U.S. who now live in areas exceeding the new O3 and particulate matter standards, and will therefore also benefit from the rapid implementation of these air quality standards. Thus, these New York City effects are best viewed as an indicator of a much broader spectrum of the avoidable adverse health effects being experienced by the nation today as a result of ongoing air pollution exposures.

Unfortunately, despite the fact that the new, more health protective ozone and particulate matters were set nearly 7 years ago, we have not made progress towards meeting those standards. As shown in Figure 3 below, ozone levels have been flat over the last decade, even rising slightly in the last ten years, with a majority of U.S. air quality areas in non-compliance with the new ozone air quality standard. Among the worst areas, in terms of change over the last two decades is EPA's Midwest Region 5, including Ohio. We need to rapidly bring polluted areas into compliance with the new air quality standards if we are to adequately protect the U.S. public's health.

Figure 3. Progress on U.S. Ozone Air Quality Has Stalled

Similarly, as shown in Figure 4, while there was historical progress in reducing fine particle levels as a result of the states' command and control regulations and the U.S. EPA's SO2 emissions trading/cap programs, this progress has slowed significantly since 1995. As noted in the figure, the areas of the country where regional particulate matter levels are worst are: the Midwest, the Southeast, and in California. The problems in California can be expected to improve in future years as low sulfur fuels and diesel controls are implemented, but the problems in the Eastern U.S. will not significantly improve until SO2 and NOx emissions from the unregulated coal-fired power plants are controlled.

Figure 4. Progress on U.S. PM2.5 Levels Have Slowed Since 1995

Thus, it is important for committee members to realize that the downside to any further delay in controlling these pollutants is that these pollutants' adverse health effects will continue to occur unabated.

Therefore, we must move forward in a vigorous fashion to achieve the new PM2.5 and ozone standards throughout the nation as quickly as possible. If we don't, then the U.S. public will unnecessarily continue to bear the ongoing diminished quality of life and the health care costs we presently pay because of the adverse health effects of these air pollutants.

Thank you for the opportunity to testify on this important issue.


Lall R., Kendall M., Ito K., and G. Thurston (2004). "Estimation of Historical Annual PM2.5 Exposures for Health Effects Assessment". Accepted for publication in: Atmospheric Environment.

Pope, C.A. III, Burnett, R.T., Thun, M.J., Calle, E.E., Krewski, D., Ito, K., and Thurston, G.D. Lung cancer, cardiopulmonary mortality and long-term exposure to fine particulate air pollution. J. Am. Med. Assoc. (JAMA) 287(9):1132-1141 (2002).

Schwartz, J. (1997) Health effects of air pollution from traffic: ozone and particulate matter. Health at the Crossroads: Transport Policy and Urban Health, T. Fletcher and A.J. McMichael Eds., John Wiley and Sons Ltd., New York, NY.

Thurston, G.D. (1997) Testimony before the Committee on Environment and Public Works. Clean Air Act: Ozone and Particulate Matter Standards. Hearings Before the Subcommittee on Clean Air, Wetlands, Private Property and Nuclear Safety. 105th Congress. ISBN 0-16-055638-4. U.S. GPO, Washington, D.C.

U.S. EPA. (2003) Latest Findings on National Air Quality: 2002 STATUS AND TRENDS, Office of Air Quality Planning and Standards, EPA 454/ K-03-001, August 2003, RTP, NC.

U.S. EPA (2003) Fourth External Review Draft of Air Quality Criteria for Particulate Matter (June, 2003). EPA/600/P-99/002aD. National Center for Environmental Assessment-RTP OfficeOffice of Research and Development. Research Triangle Park, NC

George D. Thurston, Sc.D.