Hazardous air pollutants (HAPs), also referred to as air toxics, are pollutants that can cause severe health effects and/or ecosystem damage. Serious health risks linked to HAPs include cancer, immune system disorders, neurological problems, reproductive effects, and birth defects. The Clean Air Act (CAA) lists 188 substances as HAPs and targets them for regulation in section 112 (b) (1). The air toxics program complements the NAAQS program. Examples of HAPs are benzene, dioxins, arsenic, beryllium, mercury, and vinyl chloride.
Major sources of HAP emissions include transportation vehicles, construction equipment, power plants, factories, and refineries. Some air toxics come from common sources. For example, benzene emissions are associated with gasoline. Air toxics are not subject to intensive national monitoring; the EPA and state environmental agencies monitor air toxic levels at approximately three hundred sites nationwide.
In 2003 the EPA launched the National Air Toxic Trend Site (NATTS) network. It is designed to follow trends in high-risk air toxics such as benzene, chromium, and formaldehyde. In March 2005 the EPA Office of Inspector General reported on the progress made by the NATTS program ("Progress Made in Monitoring Ambient Air Toxics, but Further Improvements Can Increase Effectiveness," March 2, 2005). The report noted twenty-three national sites had been set up to perform NATTS monitoring. The EPA has also awarded grants to state and local environmental agencies to conduct short-term monitoring of air toxics. The report recommended that the EPA focus more attention on locating NATTS monitors in areas of the country where air toxics are estimated to have the highest health risks.
national air toxic assessment. In May 2002 the EPA released the latest findings from its National Air Toxic Assessment. The data, which are for 1996, show that approximately 4.6 million tons of air toxics were released into the air, down from a baseline value of six million tons for 1990-93. Air toxics were emitted from many sources, including industrial and mobile (vehicles and nonroad equipment) sources. The known carcinogens posing the greatest risks to human health were benzene and chromium. The suspected carcinogen showing the greatest risk was formaldehyde.
the toxics release inventory. The Toxics Release Inventory (TRI) was established under the Emergency Planning and Community Right-to-Know Act of 1986. The TRI program requires annual reports on the waste management activities and toxic chemical releases of certain industrial facilities using specific toxic chemicals. The TRI list includes more than 650 toxic chemicals.
In May 2005 the 2003 Toxics Release Inventory (TRI) Public Data Release Report was published. There were nearly 4.44 billion pounds of chemical releases reported by covered facilities during 2003. The vast majority of the releases (88%) were on-site releases to air, land, and water. The remainder were off-site releases (when a facility sends toxic chemicals to another facility where they are then released). On-site air emissions amounted to 1.59 billion pounds and accounted for 40% of the total.
clean air mercury rule. Mercury is a hazardous air pollutant that can fall out of the atmosphere into water supplies where it is absorbed by fish and shellfish. Consumption of contaminated fish and shellfish is the primary source of mercury exposure to humans.
Figure 2.13 shows the primary sources of mercury emissions to air in the United States for 1990, 1996, and 1999. Emissions from medical waste incinerators and municipal waste combustors declined significantly over this time period. Emissions from miscellaneous sources, such as gold mines and industrial operations, experienced modest decreases. This leaves coal-fired boilers at electric utility plants as the largest single source of mercury emissions.
In March 2005 the EPA issued the Clean Air Mercury Rule (CAMR) to limit and reduce mercury emissions from coal-fired power plants. The CAMR program will be based on a cap-and-trade system that will be fully implemented by 2018 and should reduce mercury emissions to fifteen tons per year. According to the EPA, the United States is the only country in the world that regulates mercury emissions from utilities.
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