In the 1960s, there were a number of visible signs that pollution urgently
needed to be addressed. One of these signs was the brown air that was
engulfing so many of our nation's cities. In 1970, the Environmental
Protection Agency (EPA) was established and significant amendments to
the 1963 Clean Air Act (CAA) were made, setting the stage for a new era
of "command and control" policies to try to turn the tide on what was the
increasingly threatened state of our air. The policies that have been developed
over the years have attempted to address air pollution in a comprehensive
manner by reducing air pollutants from their many sources: mobile
sources (automobiles and trucks), fixed site facilities (factories, waste treatment
facilities, power plants), and through consumer products such as
refrigerants in refrigerators, aerosol spray cans, and other products that
threaten air quality. We are also developing a better understanding of the
association between poor air quality and human and ecological health.
The results of the CAA are noted in some improvements in air quality,
although these improvements are neither uniform for all forms of air pollution
nor consistent globally. Ground-level ozone continues to persist at
unhealthy levels in many areas, as do sulfur dioxide and mercury from
coal-fired power plants. Sulfur dioxide continues to be a major contributor
to acid rain. Although visibility has improved over many U.S. cities, it
is worsening in many third world cities. Airborne persistent organic pollutants
(POPs) are not deterred by national boundaries and are carried and
deposited based on dominant weather patterns.
The CAA required that a set of standards be created that would protect
sensitive populations, such as people who suffer with asthma. These health- based standards are the National Ambient Air Quality Standards (NAAQS).
In 1996, 46 million Americans still lived in areas where the air did not
meet the NAAQS, evidence of our need for continued air quality vigilance.
When the CAA was amended in 1990, Congress additionally mandated
the EPA to regulate "hazardous air pollutants" (HAPs) or air toxics, those
chemicals known or suspected to cause serious health problems. The
amendments named 189 toxic air pollutants for which standards must be
created, many of which are carcinogens, mutagens, and/or reproductive
toxins, including beryllium, mercury, asbestos, vinyl chloride benzene,
arsenic, and radionuclides. Such toxic air pollutants may be gases, metals
and other fine particles, and gases absorbed onto fine particles. Congress
also tightened controls on contributors to acid rain, increased measures for
controlling airborne carcinogens, created cleanup schedules for cities that
were not complying with the NAAQS, and tightened standards for auto
Air pollution sources are described by the location from which they
emanate and by the patterns of their releases. Point source refers to a specific
location such as a smoke stack. Area sources refer to pollutants that
come from a range of smaller generators such as dry cleaners (perchlorethylene),
automobiles, gas stations (benzene), and wood stoves.
Routine releases occur "continuously," certain production activities cause
the release of intermittent emissions known as "batches," and "accidental"
releases occur during explosions, equipment failure, or transportation
accidents. Traffic-related pollution may be referred to as a mobile source!