products is inconclusive. The widely quoted studies indicating severe impact of sulfates resulting from the atmospheric transformation of sulfur dioxide emissions are seriously flawed. On the other hand, there is also no evidence to suggest conclusively that present standards are too tight, or even that there are no health risks at present ambient levels. The present regulatory strategy must be considered as conservative in the light of existing evidence, but probably justified in view of the prospective rapid growth in the use of coal, especially for electric power generation, and the much higher cost of retrofit compared with tight standards on new plants. The case for conservatism is reinforced by the prospect that the largest growth in electric generation is likely to occur during the next 15 years, with a slowdown thereafter, as suggested by the various CONAES scenarios. Moreover, the possibility of a slowdown or even a moratorium on nuclear growth owing to public opposition also argues for holding coal emissions as low as practical in case coal expansion has to take place at an even greater rate than projected in the CONAES estimates.

The one emission whose effect is independent of siting is carbon dioxide. Increasing fossil fuel combustion will increase carbon dioxide emissions and tend to raise the level of carbon dioxide in the atmosphere. This problem is discussed under “Global Climate.”

Research on the Health Effects of Air Pollutants The setting of national air quality standards was a landmark in the history of public health protection in this country. The original standards were selected in 1970 by reviewing the available epidemiological and clinical evidence, deciding on a level at which a minimal effect was observed in man, and setting the standard at a level below it.7377 For the fossil fuels, the major designated pollutants that emanate from stationary sources are the particulates,78 sulfur oxides,7981 and nitrogen oxides.8284 For the mobile sources85 they are ozone,86 carbon monoxide,87 nonmethane hydrocarbons,88 nitrogen oxides, and as a secondary product, photochemical oxidants.89 Toxicity was judged by excess morbidity, primarily of the respiratory system, by excess mortality occurring during major fog pollution episodes, or on a daily or other short-term basis associated with fluctuations in the sulfur dioxide and particulate levels over the course of a year or more.

In addition, it had been recognized that coal tar is a classical source of chemical carcinogens. An excess of cancer had been demonstrated as an occupational hazard in certain industrial operations where the workers were heavily exposed to fumes from coal processes90 (present-day practices would reduce such exposure). These carcinogens may include mutagens. Control of particulates would presumably diminish exposure of the public to the chemical carcinogens and mutagens released by combustion. It is

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