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Air pollution from power plants was the focus of a 2004 report by the North American Commission for Environmental Cooperation (CEC). Power plants accounted for 46 of the top 50 stationary sources of air pollution in North America in 2001, and they generated 45 per cent of the 755 502 tonnes of toxic air releases (CEC 2004a).
The release of chemicals to the air is the most common type of emission in North America. The largest air release was of hydrochloric acid, primarily from electric utilities burning coal and oil.
There was an encouraging 20 per cent decline in on-site air releases in the United States between 1998 and 2001 (Figure 2). The electric utilities industry, the largest source of toxic air releases of any industry sector, reported a decrease of 10 per cent during the period.
In Canada, by contrast, on-site air releases increased by 2.6 per cent over this period. The paper products industry reported a 5 per cent increase. Factors contributing to the increase included changes in estimation methods, increased production, and new facilities reporting in 2001 (CEC 2004a).
Persistent bio-accumulative toxic chemicals are another significant class of toxic release - principally mercury and its compounds (CEC 2004b). Coal and oil-fired power plants accounted for almost two thirds of the 43 384 kg of mercury air emissions from North American industrial facilities. Total releases of mercury fell 48 per cent from 2000 to 2001 (CEC 2004b). In Canada, most mercury emissions come from zinc smelting and garbage incineration (CEC 2004a). Governments in both countries are examining ways to further reduce mercury emissions from coal-fired electrical generation facilities (IJC 2004).
Despite the decrease in emissions, mercury is still building up in the food chain. Micro-organisms in water help convert it to methyl mercury, which travels up the food chain, accumulating in fish and animal tissues. At sufficient levels, it has highly toxic effects for birds and mammals, including brain and nerve tissue damage, cardiovascular effects and kidney damage (IJC 2004). Children exposed to methyl mercury in the womb can have problems later with language, memory, fine motor function, and other neurobehavioral tasks (EPA 2004b).
In March 2004, the EPA and the US Food and Drug Administration issued a joint consumer advisory about the levels of mercury in fish and shellfish, and the quantities and frequency with which they can be eaten safely (FDA and EPA 2004). The goal is to reduce exposure to mercury in women who are, or may become, pregnant, nursing mothers, and young children (IJC 2004).
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