achievable national air quality standards. ⁵ Enforcement of these standards
was left up to the individual states, which were required to compose formal
plans of implementation.

The focus of the Clean Air Act was on criteria pollutants as opposed to
hazardous pollutants. Criteria pollutants are relatively common pollutants
found throughout the United States and are dangerous in large concentra-
tions. ⁶ Primary national air quality standards were established for six such
major pollutants by the EPA, based on the requirements of the Clean Air
Act. These pollutants are: total suspended particulates, sulfur dioxide, car-
bon monoxide, photochemical oxidants, nitrogen dioxide and hydrocar-
bons. Primary standards are standards set to protect human health, and
these standards, which were based on the 1970 Act, were supposed to be
achieved by mid-1975. ⁷

Secondary standards were also supposed to be set by the EPA for these
pollutants. The purpose of these standards was to protect other aspects of
human welfare by enhancing the quality of life, including aesthetic aspects,
physical objects and vegetation. ⁸ By 1975, the only secondary standard that
had been set was for total suspended particulates; by 1987, sulfur dioxide
also had been assigned a secondary standard. Secondary standards are more
stringent than primary standards. For example, the primary standard for
particulates is 75 μ g/m3, annual geometric mean, while the secondary stan-
dard is 60.

The Clean Air Act also required that new sources of pollution meet strin-
gent air quality standards. These new sources include automobiles and
power plants. Automobile manufacturers were originally given until 1975 to
meet the emission standards. This was subsequently postponed until 1978.
As a result of the Clean Air Act, the United States was divided into 247 Air
Quality Control Regions. ⁹ Monitoring sites were to be set up in each region
to ensure that environmental officials there were aware of any variance from
the national ambient air standards.

In 1977 the Clean Air Act was amended, mainly so that the emission stan-
dards for 1978 automobiles could be relaxed. ¹⁰ However, the 1977 Amend-
ments also focused on a number of issues pertaining to national ambient air
standards. Clean air areas were divided into three classes: class I, where little
deterioration in air quality would be allowed; class II, where moderate dete-
rioration in air quality would be permitted; and class III, where significant
deterioration would be allowed. ¹¹ Basically, what was being permitted was
that in areas that were cleaner than the national air quality standards, new
industry could pollute at a level that either met or exceeded (depending on
the class) the current pollution level. Class I areas were designated by Con-
gress as National Parks and Wilderness areas, while class II areas are all
other areas except those designated as class I or III by the state governor. ¹²

The 1977 amendments also extended the deadline for meeting the national
ambient air standards until 1982 and, in some cases, until 1987. However,

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