|
The decision to adopt new national ambient air quality standards for "fine" particulate matter and ozone did not
come easily. Under the 1990 federal Clean Air Act, the EPA is expected to revisit its standards once every five years to make sure they are adequately protecting the public's health. Since
1987, when the PM10 standard was adopted, an impressive body of evidence had developed through studies which indicated that people's health was affected by PM10 even at concentration
levels well below the standards. Furthermore, these scientific studies found that fine particles of 2.5 microns or less penetrate deeper into lungs and are therefore more likely to contribute
to adverse health effects.
These health effects include:
- premature death and increased hospital admissions and emergency room visits;
- increased respiratory symptoms and disease;
- decreased lung function; and
- alterations in lung tissue and structure and in respiratory-tract defense mechanisms.
Similarly, the ozone standard was last revised in 1979, and, since the late 1980s, thousands of studies have been
published on the health and ecological effects of ozone. These studies suggest that present standards do not protect health and the environment, in part because the 1-hour standard protects
the public against peak highs but not against sustained exposure to high ozone levels. The congressionally mandated Clean Air Scientific Advisory Committee concluded that the studies and
issues provided an adequate basis for revision of the primary and secondary standards for both particulate matter and ozone.
In November 1996 the EPA published its proposal to revise ozone standards, setting a proposed 8-hour ozone standard of .085
parts per million, based upon taking the third highest 8-hour ozone concentration each year and then averaging these over a three-year period. In December 1996 the EPA announced a new
proposed PM2.5 daily standard of 15 micrograms per cubic meter (µg/m3) and a 24-hour PM2.5 standard of 50 µg/m3. More than 50,000 comments were received from industries, environmental groups,
local government officials, congressional representatives, and the public. Finally, on July 17, 1997, the EPA adopted the new standards, although it raised the proposed PM2.5 24-hour standard
from 50 to 65 ug/m3 and changed the 8-hour ozone exceedence level from the third to the fourth highest 8-hour ozone concentration each year. These two changes weakened the standards initially
proposed in December 1996, but the new standards still drew heated opposition from some industry sectors and has led to court cases against it.
(Source: Information from EPA, Regulatory Impact Analysis of New Ozone and Particulate Matter Air Quality Standards [July
17, 1997]; EPA, Summary of EPA's Strategy for Implementing New Ozone and Particulate Matter Air Quality Standards Fact Sheet, July 17, 1997.)
|
