Health Effects of Particulate Air Pollution
Section snippets
What is Particulate Air Pollution?
In the simplest terms, particulate air pollution is anything solid or liquid suspended in the air. It includes smoke, fumes, soot, and other combustion by-products, but also natural particles such as windblown dust, sea salt, pollen, and spores. It includes primary particles coming directly out of exhaust stacks and tailpipes, but also can include secondary particles, such as sulfates and nitrates, which form from condensation of vaporized materials or from the by-products of the oxidation of
Early Epidemiology and Regulation
The goals of early air pollution legislation in the United States were broad and general, but called for a science-based approach to control. The 1970 Clean Air Act required identification of pollutants which “may reasonably be anticipated to endanger public health and welfare”. The Act required the government to establish criteria which “accurately reflect the latest scientific knowledge useful in indicating the kind and extent of all identifiable effects on public health and welfare” (section
Review of the EPA Particle Standard
The Clean Air Act requires the EPA to periodically review the ambient air quality standard based on the latest scientific knowledge of health effects, but the epidemiology evidence remained limited. Nevertheless, in 1987 the EPA replaced the TSP standard with a standard for particles smaller than 10 μm (PM10) (9). This standard was based on dosimetric studies that had shown that particles larger than PM10 did not penetrate the body's defenses in the nose, mouth, and upper airways and were
Time Series Studies
In the 1980′s, analyses of counts of daily mortality in London had found inconsistent associations with concurrent particle (Black Smoke) measurements (14). Drs. Joel Schwartz and Allan Marcus of the EPA Reanalyzed the London daily mortality data using a time series approach (15). These new analyses showed increased daily deaths associated with daily Black Smoke concentrations down to the lowest observed concentrations. However, because of the uniqueness of this approach, the different
Studies of Effects of Long-Term Particle Exposures
While the epidemiologic evidence was strong for a causal link between episodically elevated particulate air pollution and daily mortality, the question remained whether these associations represented substantial life-shortening and whether repeated or chronic exposures to elevated PM were associated with additional risks.
The prospective follow-up of the sample of adults in the Harvard Six Cities study provided an opportunity to examine survival associated with city-specific mean air pollution
EPA Forced to Act
The Clean Air Act requires that the standards be reviewed every 5 years to reflect the latest scientific knowledge. The EPA last had reviewed the particle standard in 1987. Based on the epidemiologic evidence from the time-series and prospective cohort studies that appeared in the early 1990′s, the American Lung Association sued EPA in federal court in 1994 to force the agency to review the PM10 standard (39). The court ordered the EPA Administrator to review the particle air quality standard
1997 Decision and Subsequent Research
In the meantime, the review of the particle standard required by the court continued, and in 1997 the EPA promulgated a new standard for PM2.5(48). The decision to regulate PM2.5 was still based largely on the epidemiologic evidence. As part of that decision, the EPA asked the National Research Council to convene a panel to evaluate the research needs in other fields of science, such as toxicology, to more fully understand particulate air pollution exposures and health effects. As a result
Lessons
Epidemiology played a key role in identifying a major threat to public health and provided key information that led to standards for particulate pollution that are having a substantial beneficial effect on public well being. Vested interests fought those standards by attacking the epidemiologic evidence in general and specific key studies. Ultimately those attacks failed, but they delayed regulations that would have provided greater health protection for the public. Many public health issues
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