One of the more significant air pollutants impacting the Northeast is photochemical smog. Smog is a composed of a wide variety of constituents that include ozone, nitrogen oxides (including nitric acid), PANs (peroxyacetyl nitrates), and VOCs (volatile organic compounds, including formaldehyde). Many of the components are highly reactive and can damage living biological tissue as well as other materials such as rubber, metals, and textiles. The components of photo- chemical smog are formed when hydrocarbons and nitrogen oxides react in the atmosphere under the influence of sunlight, hence the term "photochemical." The primary sources of the pollutants that react to form smog are fossil fuel-burning power plants and internal combustion engines (both vehicular and others such as outboard motors and lawnmowers). Because of the photochemical nature of smog formation, ozone is primarily, but not exclusively, a summer air pollutant.
Ozone and nitrogen oxides are two components of smog that are monitored and regulated under the Federal Clean Air Act's National Ambient Air Quality Standards (NAAQS). From 1986 to 1995 emissions of nitrogen oxides have only decreased by 3%. Concentrations of ozone in the U.S. have declined by only 6% over the same period. Large areas of the northeast continue to exceed the NAAQS for ozone for much of the summer.
It should be understood that ozone in the current context is ozone that occurs at "ground-level" in the troposphere where it is a harmful air pollutant. Ozone that occurs in the stratosphere forms the protective "ozone layer." These differences in location determine whether the ozone is beneficial or harmful.
One factor that seriously complicates reduction of photochemical smog in the Northeast is that the pollutants that give rise to smog and components of smog (i.e., ozone) may be transported great distance by prevailing winds. For example, during the summer, air over parts of the rural, pristine coast of Maine, that include Acadia National Park, routinely exceed the NAAQS for ozone. The pollution is not produced in Maine, but is transported from the urbanized, industrialized region from Boston south to Washington, D.C.
The control and management of the northeast's smog problem has become a regional undertaking. The Federal 1990 Clean Air Act established the Ozone Transport Commission (OTC) and the Northeast Ozone Transport Region (http://earth1.epa.gov/oar/oaqps/airtrans/regional.html). The OTC includes representatives from the US EPA, 12 states (Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Pennsylvania, Maryland, Delaware, and Virginia), and the District of Columbia. To combat ozone problems, the OTC and the Ozone Transport Assessment Group (OTAG) have developed elaborate computer models to determine sources of primary pollutants and to estimate the formation and transport of photochemical smog throughout the region (http://capita.wustl.edu/OTAG/Reports/Otagrept/ otagsum3.html).
In order to reduce the concentrations and occurrences of ozone and photochemical smog in the northeast, a wide variety of solutions must be implemented. The OTC states have established a goal of reducing nitrogen oxide emissions by approximately half of 1990 levels by the year 1999. Since one of the major sources of nitrogen oxides are vehicles, much of the cleanup effort is focussed on cleaner automobiles and methods to reduced the number of miles driven. In addition, because of concerns over the effects of ozone on human health the EPA has promulgated a more stringent (i.e., lower) NAAQS for ozone.
The concern over ozone and the efforts to reduce the chemical pollutants, which produce ozone, is filled with controversy:
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