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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).

Figure 2: On-site air emissions

Source: CEC 2004b

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).

Box 1: Fine particulates - new evidence and new regulations

New policies are being put in place in the United States to reduce emissions of fine particulates, following strong evidence of the threat that they pose to human health.

In 2004, the EPA released the findings of a 5-year intensive research programme on the effect of fine particulate matter (PM2.5) on human health in the US. Exposure to ambient particulate matter was associated with increases in respiratory health problems, hospitalizations, and premature deaths. The research also found that fine particles move indoors, that people already suffering from lung disease collect more particles in their lungs, and that PM2.5 also affects the heart. The EPA report pointed out that there is a need for improved air quality standards to reduce fine particulates in the air (EPA 2004c).

Three new regulations will soon be in place to help prevent particulates from entering the air:

  • Finalization of the United States Clean Air Interstate Rule would reduce emissions of sulphur dioxide (SO2) and nitrogen oxides (NOx), the two most important precursors to PM2.5. The proposed rule focuses on states whose air pollution causes problems in other downwind states. It requires them to meet specific emission reductions. It covers 29 eastern states and the District of Columbia (EPA 2004d). It was not clear at the time of going to press whether this rule would be enacted;
  • By December 2004, the EPA will make final designations identifying places with air quality levels that exceed national standards. The EPA designates an area as 'nonattainment' if it has violated the fine particle standards over a three-year period, or if relevant information indicates that it contributes to violations in a nearby area. In mid-2004, the EPA identified 243 counties, with 99 million inhabitants, where the national air quality standard for fine particulate matter was violated. Within three years, states and local governments must develop implementation plans showing how they will meet the PM2.5 standards (EPA 2004e). Environmentalists are pressing for more comprehensive protection, including strengthening the control of power plant emissions, which they say cut short the lives of nearly 24 000 people each year (Schneider 2004); and
  • The Clean Air Nonroad Diesel Rule will also help to reduce PM2.5. It requires stringent pollution controls on diesel engines used in industries (EPA 2004b).

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