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Pollution: United States
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Pollution is a major problem across the United States. More than half of all Americans live in areas with unhealthy levels of outdoor smog or particle air pollution, according to a study by the American Lung Association. In addition, indoor air pollution such as secondhand smoke and combustion byproducts can present health risks.
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By the 21st century, pollution had evolved from a mainly localized problem to one of global consequences in which pollutants not only persisted in the environment, but changed atmospheric and climatic conditions. The Minamata Bay disaster was the first major indication that humans would need to pay more attention to their waste products and waste disposal practices, in particular, hazardous waste disposal. In the years that followed, many more instances of neglect or carelessness resulted in dangerous levels of contamination. In 1976 an explosion at a chemical factory in Seveso, Italy, released clouds of toxic dioxin into the area, exposing hundreds of residents and killing thousands of animals that ate exposed food. In 1978 it was discovered that the Love Canal housing development in New York State was built on a former chemical waste dump. The development was declared uninhabitable.
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In both developed and rapidly industrialising countries, the major historic air pollution problem has typically been high levels of smoke and sulphur dioixide arising from the combustion of sulphur-containing fossil fuels such as coal for domestic and industrial purpose. The major threat to clean air is now posed by traffic emissions. Petrol and diesel-engined motor vehicles emit a wide variety of pollutants, principally carbon monoxide (CO), oxides of nitrogen (NOx), volatile organic compounds (VOCs) and particulates (PM10), which have an increasing impact on urban air quality. In addition, photochemical reactions resulting from the action of sunlight on nitrogen dioxide (NO2) and VOCs from vehicles leads to the formation of ozone, a secondary long-range pollutant, which impacts in rural areas often far from the original emission site. Acid rain is another long-range pollutant influenced by vehicle NOx emissions. In all except worst-case situations, industrial and domestic pollutant sources, together with their impact on air quality, tend to be steady-state or improving over time.
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Air pollution may have a silver lining in some parts of the United States -- it might help make summer weekends less rainy, according to a new study. Scientists have long questioned whether particulate pollution from vehicles and factories, which is higher during the workweek, changes weather patterns. The study, published Thursday in the Journal of Geophysical Research -- Atmospheres, found that tiny particulate matter from workweek pollution may "seed" summer clouds in
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Such simple treatment for environmental pollution on a wider scale might have had greater merit in earlier centuries when physical survival was often the highest imperative, human population and densities were lower, technologies were simpler and their byproducts more benign. But these are often no longer the case. Furthermore, advances have enabled measurement of concentrations not possible before. The use of statistical methods in evaluating outcomes has given currency to the principle of probable harm in cases where assessment is warranted but resorting to deterministic models is impractical or unfeasible. In addition, consideration of the environment beyond direct impact on human beings has gained prominence.
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Modern landfills attempt to minimize pollution of surface and groundwater. They are now located in areas that will not flood and that have the proper type of soil. Solid wastes are compacted in the landfill and are vented to eliminate the buildup of dangerous gases. Hazardous wastes, including toxic chemicals and flammable, radioactive, or biological substances, cannot be deposited in landfills, and the management of these wastes is subject to federal and state regulation. The federal government's Resource Conservation and Recovery Act (42 U.S.C.A. § 6901 et seq.) is a comprehensive regulatory statute that creates a "cradle to grave" system of controlling the entire hazardous waste life cycle.
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