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Show INTRODUCTION Nitrogen oxides (NOx), principally nitric oxide (NO) and nitrogen dioxide (NO2), are atmospheric pollutants having the potential for direct and indirect adverse effects on human health and welfare. Human activity originates emissions resulting in N0X concentrations in urban atmospheres that are 10 to 100 times higher than those from natural sources in nonurban areas. Fuel combustion in equipment contributes about 99 percent of technology-associated N0X emissions. For most equipment about 95 percent of the N0X is emitted as NO and 5 percent as NO2. In the atmosphere, N0X enters into complex photochemical reactions with hydrocarbons and sulfur oxides and results in the formation of undesirable secondary species, with a shift of residual NO to NO2. The adverse effects of NO2 and other pollutants on humans, animals, vegetation, and exposed materials were among the factors which led to passage of the Glean Air Act of 1970. With respect to N0X, this Act empowered the EPA (a) to establish primary and secondary National Ambient Air Quality Standards (NAAQS) for NO2, (b) to require a 90 percent reduction in N0X emissions from light duty motor vehicles, (c) to establish New Source Performance Standards (NSPS) for stationary sources, (d) to set up mechanisms to ensure compliance and enforcement, and (e) to provide research, development, and demonstrations of new and improved, commercially viable methods for the prevention and control of pollution from the combustion of fuels. The Clean Air Act Amendments of 1977 require EPA (a) to revise the NAAQS for NO2 to consider short term effects (not more than 3 hours), (b) to implement a revised level of automotive N0X control, (c) to require NSPS based on use of the best technological continuous emission controls, and (d) to promulgate regulations for prevention of significant deterioration of air quality. The Amendments also require that any conversion of sources to coal firing be environmentally acceptable. 3-1 |
