Prevention of Significant Deterioration (PSD)

Prevention of Significant Deterioration (PSD) Of all the federal laws placing environmental controls on industry (and, in particular, on new plants), perhaps the most confusing and restrictive are the limits imposed for the prevention of significant deterioration (PSD) of air quality. These limits apply to areas of the country that are already cleaner than required by ambient air-quality standards. This regulatory

framework evolved from judicial and administrative action under the 1970 Clean Air Act and subsequently was given full statutory foundation by the 1977 Clean Air Act Amendments.

 

EPA established an area classification scheme to be applied in all such regions. The basic idea was to allow a moderate amount of industrial development but not enough to degrade air quality to a point at which it barely complied with standards. In addition, states were to designate certain areas where pristine air quality was especially desirable.

All air-quality areas were categorized as Class I, Class II, or Class III. Class I areas were pristine areas subject to the tightest control.

 

Permanently designated Class I areas included international parks, national wilderness areas, memorial parks exceeding 5000 acres, and national parks exceeding 6000 acres. Although the nature of these areas is such that industrial projects would not be located within them, their Class I status could affect projects in neighboring areas where meteorological conditions might result in the transport of emissions into them. Class II areas were areas of moderate industrial growth.

 

Class III areas were areas of major industrialization. Under EPA regulations promulgated in December 1974, all areas were initially categorized as Class II. States were authorized to reclassify specified areas as Class I or Class III.

 

TABLE 25-1 National Primary and Secondary Ambient Air Quality Standards

 

 

Pollutant	Averaging time	Primary standards	Secondary standards
Sulfur oxides	Annual arithmetic mean 24h 3h	80 mg/m3 (0.03 ppm) 365 mg/m3 (0.14 ppm)	300 mg/m3 (0.5 ppm) 60 mg/m3
Particulate matter (PM10, particulates with aerodynamic diameter less than or equal to 10 microns)	Annual geometric mean 24 h	75 mg/m3 260 mg/m3	150 mg/m3
Ozone	1 h	240 mg/m3 (0.12 ppm)	Same as primary standard
Carbon monoxide	8 h 1 h	10 mg/m3 40 mg/m3 (35 ppm)	Same as primary standard
Nitrogen oxides	Annual arithmetic mean	100 mg/m3 (0.05 ppm)	Same as primary standard
Lead	3 months	1.5 mg/m3	Same as primary standard