Environmental Engineering FOURTH EDITION

Air Pollution Law 4 19

NO, are:

0 4.2 g/mile for CO,

0 0.6 g/mile for NO,, and

0 0.31 @mile for nonmethane hydrocarbons.

These standards were phased for model years 1994 to 1996. Gasoline-powered

automobiles from 1997 to 1999 model years were required to meet the following

0 3.4 g/mile for CO,

0 0.4 g/mile for NO,, and

0 0.25 g/mile for nonmethane hydrocarbons.

In addition, light-duty diesel powered vehicles newer than 1996 were required to

meet the 1996 emission standards. EPA has proposed that, by 2004, gasoline-powered

vehicles will meet emission standards that are twice as stringent as these. Standards

are also set for diesel-powered trucks, oxygenated fuels, vehicles that operate at high

altitudes, and so on. Detailed discussion of these is beyond the scope of this text. The

reader is referred 40 CFR Part 86 for further details.

TROPOSPHERIC OZONE

The 1990 Clean Air Act requires each state to establish categories of ozone nonattain-

ment areas. Reasonably available control technologies (RACT) are to be required for

all air polluters in such areas, depending on the degree of nonattainment. Requirements

for using RACT are summarized in Table 21-5. Each state must classify areas rela-

tive to nonattainment for ozone concentration. RACT includes the use of oxygenated

fuels, and many states now require suppliers to sell only oxygenated fuels from October

through March each winter.

ACID RAIN

Fossil fuel electricity generating facilities have been seen as the major contributors

to the acid rain problem; the 1990 Clean Air Act acknowledges the importance of

Table 21-5. Size of Pollution Sources That Must Use RACT

Size of pollutant source that

Level of nonattainment must use MCT (tons/year)

Extreme

Severe

Serious

Moderate

10

25

50

100