Hazardous air pollutant, 1970-2017

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A hazardous air pollutant is considered toxic because it may contribute to serious health effects, such as cancer, birth defects, respiratory illness, and other maladies. Hazardous air pollutants are released from human activity, such as industrial activities like oil refining, and from natural sources, such as forest fires and volcanic eruptions. Examples of hazardous air pollutants include benzene, mercury, cadmium, methylene chloride (an industrial solvent), and hydrochloric acid.^[1]

Background

Hazardous air pollutants are emitted from natural and human-made sources, including volcanoes, wildfires, motor vehicles, industrial facilities, and oil refineries. These pollutants are considered toxic compared to other air pollutants because exposure to them at a sufficient concentration and duration is known or suspected to increase the risk of certain health problems, such as cancer, heart disease, respiratory illness, and reduced fertility. The likelihood of health problems caused by exposure to hazardous air pollutants varies depending on pollutant concentration and length of exposure. For example, the immediate inhalation of a hazardous air pollutant may produce a minor effect, such as water eyes, or a more serious effect, such as lung damage. Further, individuals exposed to hazardous air pollutants may not experience health effects for months or more, as in the case of cancer.^[2][3]

Types of chemicals

See also: Air pollutants

Below is a partial list of chemicals that are considered hazardous air pollutants at certain levels of exposure:^[3]

• Benzene is a petrochemical and a natural component of crude oil, coal, and natural gas. Sources of benzene exposure include auto exhaust, gasoline, and forest fires. Benzene is used in industrial activities as a raw material to produce chemicals, lubricants, dyes, rubbers, pharmaceuticals, and detergent. Benzene is also used in households as a solvent in paints and varnishes. Benzene exposure is regulated in industrial activities by the U.S. Occupational Safety and Health Administration (OSHA). Industrial facilities use ventilation and require employees to use safety gear in order to limit benzene exposure.^[4]
• Methylene chloride is a colorless liquid that is used in households and in industrial activities. It is used a solvent in paint and varnish strippers and in food and beverage manufacturing. Methylene chloride is also used to degrease metal surfaces in airplanes and on railroad equipment, to lubricate automobile parts, and to extract chemicals from plants to produce antibiotics and vitamins. Methylene chloride exposure in industrial activities is limited under federal regulations. Workers cannot be exposed to more than 25 parts of methylene chloride per million parts of air during an eight-year period. Workers also use respirators and other safety gear to protect against exposure. In addition, the U.S. Food and Drug Administration limits the amount of methylene chloride that can remain in food products.^[5]
• Asbestos is a group of naturally occurring minerals composed of solid fibers. Asbestos was used in building materials due to its resistant to chemicals, fire, and heat. Exposure to asbestos can cause mesothelioma, a cancer that creates thin tissues covering the lungs and the abdomen. The EPA classified asbestos as a hazardous air pollutant in 1971.^[6][7]
• Lead is a heavy yet malleable metal that is naturally occurring. Lead is used in glass, crystal, gasoline, paint, water lines, pipes, ammunition, batteries, and more. If inhaled or ingested at specific levels, it is a neurotoxin that can lead to nervous system damage and brain disorders.^[8]

Regulation

Under the Clean Air Act, hazardous air pollutants "cause or contribute to an increase in mortality or an increase in serious irreversible, or incapacitating, reversible, illness." Under the Clean Air Act of 1970 and 1977, the EPA set emissions limits for seven hazardous pollutants—beryllium, mercury, vinyl chloride, asbestos, benzene, radionuclides, and arsenic.^[9]

With the 1990 Clean Air Act Amendments, Congress revised the EPA's hazardous air pollutant program to a technology-based regulatory system. The EPA would regulate major sources of hazardous air pollutant emissions and require facilities to adopt technologies to control their emissions. Technologies used to reduce hazardous pollutants include scrubbers, filters, thermal oxidizers, and more. The standards, known as maximum achievable control technology (MACT) standards, are based on the maximum reduction of emissions achievable by new and existing sources of hazardous pollutants. The standards must also take into account costs and any non-air health or environmental impacts.^[9][10]

See also

• Glossary of environmental terms
• Clean Air Act
• Air pollutants
• National Ambient Air Quality Standards

Footnotes

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