|March 11, 1997|
Dear Ms. Nichols:
This letter transmits comments on the U.S. Environmental Protection Agency (U.S. EPA) proposals for new, national clean air goals and policies. These proposals and their associated docket numbers are: Revisions to the National Ambient Air Quality Standards for Ozone (A-95-58) and Particulate Matter (A-95-54), the Monitoring Method and Strategy for Fine Particulate Matter (A-96-51), and the Interim Implementation Policy (A-95-38), as well as the Advance Notice of Proposed Rulemaking for the Implementation Policy (A-95-38).
As a guiding principle, health-based standards must reflect the weight of scientific evidence. Additionally, the scientific debate must acknowledge unanswered questions that must be addressed with continuing scientific research. There is much at stake -- the health of millions of Americans as well as the strength of our nation's economy.
However, scientific evidence indicates that current national standards for both particulate matter less than ten microns in diameter (PM10) and for ground-level ozone do not adequately protect public health. Much of this evidence was available and used as a basis for California's own standards. The California Air Resources Board (ARB) adopted the current state ozone standard in 1987 and reaffirmed the standard in 1994. The state standard for particulate matter less then 10 microns in diameter (PM10), which includes fine particles, was adopted by the ARB in 1983. In the past few years, additional studies which produced consistent findings have been completed.
In order to address the health effects of both the fine and coarse components of respirable particulate matter, U.S. EPA could have taken California's approach of adopting a health protective PM10 standard. That way, the full spectrum of health effects associated with fine particles 2.5 microns and smaller (PM2.5) and the coarse fraction (particles between 2.5 and 10 microns) would be addressed with one standard. U.S. EPA has taken a different approach by proposing to add an additional, separate standard for PM2.5. There is a large body of health studies on PM10, which assess the combined impacts of all respirable particles, including those in the fine fraction. These studies, combined with newer community health studies that seek to isolate the effects of the fine fraction, provide evidence of harmful effects, including increased respiratory illness and premature death. Such evidence must be considered. At the same time, unanswered questions regarding the effects of respirable particulates, for both the fine and coarse components, must be addressed. Although the health studies indicate what happens when people are exposed to ambient levels of particulate matter, the science cannot yet explain the specific mechanism by which these particles cause damage. Nor has there been a clear identification of which components of the complex chemical mixture that make up atmospheric particulate matter are likely to be most harmful. There are clearly gaps in our knowledge about the mechanistic nature of particle size and chemical composition.
Community Health Studies. Many reviewers of the proposed standards see the lack of identified mechanisms of toxicity that explain the results of major research studies as a problem. However, the nature of the research that has identified the consistent associations between ambient particulate matter and health effects is not suited to answer such questions. These community health, or epidemiologic, studies focus on how people respond to various environmental stresses, under real-world conditions. They are uniquely valuable and relevant because they can identify health problems in populations and suggest linkages with possible causal factors. The complexities of life in the real-world complicate their interpretation. Other pollutants and environmental factors may stress people who are already ill and place them at risk for further illness. Community health studies should be supplemented with other studies that focus on the mechanisms of toxicity.
Association and Causation. While there are consistent findings of health effects related to particulate matter exposure, there are not yet mechanisms identified which can explain the effects. Epidemiologic studies show consistent associations, but do not establish causality. Controlled human clinical exposure studies are often found useful to establish causality of pollutant impacts. While chamber studies that exposed humans to controlled amounts of ozone have demonstrated a causal relationship with specific adverse health effects, similar studies are not feasible for particulate matter. Since respirable particulates are associated with premature death, scientists clearly cannot conduct human studies that seek to reproduce the effect. The complexity of the mixture of compounds that make up particulate matter also makes laboratory exposure studies difficult. However, additional controlled animal exposure studies should be done to address questions of mechanism.
Level of Standard. Another area of uncertainty relates to the proposed level of the standard for PM2.5. The fact that there is no clearly demonstrated safe or "no-effects" level for ambient particulate matter has made the determination of where to set standards complex. The mandate of U.S. EPA, as directed by the Clean Air Act, is to establish ambient air standards that protect the health of the population, including sensitive groups, with a margin of safety that includes consideration of uncertainties in knowledge. Several recent studies on both respirable and fine particulate matter (PM10 and PM2.5) show effects for each pollutant in even the cleanest communities. These findings are interpreted by members of the scientific community to indicate that: no safe level exists for particulate matter, studies have not yet been performed to find the safe levels, or the available scientific methods are not suitable to determine the safe level. In response to the problem of no identified safe level, U.S. EPA has taken a risk assessment approach to quantify the uncertainty and establish likely health outcomes at alternate standards levels.
Additional research will clearly be beneficial in addressing these areas of uncertainty. ARB is sponsoring two research projects to determine the impact of particle size and concentration on the frequency and severity of health effects. These studies should provide valuable information relevant to how particulate matter exerts its effects and which components are most harmful. Additional epidemiological studies are also underway to define our knowledge of how California's PM2.5, PM10, and ozone impact health. These projects are designed to meet California's needs in pursuing the most effective and reasonable control strategies, but could provide information useful to other states. Nonetheless, due to the national importance of this type of research, it is imperative that U.S. EPA meet its responsibility to pursue the targeted research program recommended by the Clean Air Scientific Advisory Committee (CASAC).
Implementation. The Advance Notice poses a series of questions and discusses a broad range of options for implementation policies that U.S. EPA must address in future rulemakings (expected in 1998 and 1999). One of the most important issues for California is the timing of new attainment deadlines.
The 1990 Clean Air Act Amendments recognized the need to provide more time for areas that faced more difficult challenges (based on the nature and severity of the problem, as well as the progress already achieved). Dates set by Congress in the 1990 Amendments have proven to be appropriate in balancing the need for rapid progress with practical constraints (except for areas dominated by transported pollutants). Implementation efforts to attain new standards should reflect the same kind of programatic approach.
U.S. EPA policies for establishing attainment deadlines for new standards should be based on these principles:
Implementation questions must be considered in a sensible, reasoned fashion. U.S. EPA's recent attempt to unilaterally develop prescriptive implementation strategies for California resulted in the untenable Federal Implementation Plan which was ultimately nullified by Congress. U.S. EPA must implement future standards in a way that takes economic impacts into account. U.S. EPA should follow California's common-sense example and develop flexible policies that allow states to pursue air quality progress in parallel with economic opportunities. As indicated earlier, California has maintained clean air standards that are more health protective than the current federal standards.
Finally, it is critical that the results of ongoing research be incorporated into the implementation process for new standards. Scientific evidence supports the adoption of more health-protective national standards. U.S. EPA should adopt new standards based on this information, and take the necessary actions to fill the current knowledge gaps in an expeditious fashion. The results of this research are needed to ensure that the implementation process produces carefully-designed, cost-effective control strategies.
If you would like to discuss these comments, please call me at (916) 445-4383.