Toxic air pollutants (TAPs) are those pollutants that are known or suspected to cause cancer or other serious health effects, such as reproductive effects or birth defects, or to cause adverse environmental effects. Some TAPs are immediately dangerous to human health even in small quantities; some TAPs cause health problems if the exposure extends over a longer period of time. The degree to which a toxic air pollutant affects a person's health depends onmany factors, including the quantity of pollutant the person is exposed to, the duration and frequency of exposures, the toxicity of the chemical, and the person's state of health and susceptibility.
Where Do Toxic Air Pollutants Come From?
Scientists estimate that millions of tons of toxic pollutants are released into the air each year. Some air toxics are released from natural sources such as volcanic eruptions and forest fires. Most, however, originate from manmade sources, including both mobile sources (e.g., cars, buses, trucks) and stationary sources (e.g., factories, refineries, power plants, and small businesses). In addition, many routine activities around the home, such as using gas-powered lawnmowers and tools, or using volatile paints and cleaning solvents, release toxic pollutants into the air.
The list of toxic air pollutants in the Clean Air Act is a long one, and it includes some familiar names, such as benzene. Benzene is a known cancer-causing substance that is a component of gasoline and some cleaning solvents. Gasoline sold in the United States is, on average, 1.6 percent benzene. Eighty-five percent of human exposure to benzene comes from gasoline. Examples of other TAPs include perchloroethylene, methylene chloride, toluene, dioxin, and metals such as mercury, chromium and lead compounds. Generally, exposure to toxic air pollutants is higher for people living near large industrial facilities or in urbanized areas, than for people living in rural areas.
The Clean Air Act is the law which drives most federal regulation of air quality, and the U.S. Environmental Protection Agency is charged with developing and enforcing the regulations. Two groups of air pollutants are regulated under the Clean Air Act. The first group, called the Criteria Pollutants, are regulated under Title I of the Clean Air Act. There are only six in this group. These pollutants -- ozone, carbon monoxide, nitrogen dioxide, sulphur dioxide, lead, and particulate matter (PM) -- are found in relatively large quantities in our lower atmosphere, particularly in populated, urban areas. They threaten human health and the environment across broad regions of the country. Under Title I, Congress set national ambient air standards for each of the criteria pollutants, based on health risk studies. (See Background Sheet #3 for more information on criteria pollutants.)
The second group are the Toxic Air Pollutants -- also called "hazardous air pollutants." Under Title III of the Clean Air Act Amendments of 1990, Congress established a list of 189 hazardous compounds known or suspected to cause cancer or other serious health effects. The regulatory program for the TAPs, or "hazardous air pollutants," in the 1990 amendments reflected an entirely new approach. Since the sources of TAPs are often specific industries, EPA must identify categories of the major industrial sources of these chemicals and then develop "maximum achievable control technology" (MACT) standards for each "source category." These standards are to be based on the best control technologies that have been demonstrated in these industrial categories. State and local air pollution agencies have the primary responsibility to make sure industrial plants meet the standards.
In setting the MACT standards, EPA looks not at health risk, but at pollution control equipment and pollution prevention methods, such as substituting nontoxic chemicals for toxic ones currently in use. Eight years after each MACT standard is issued, EPA must assess the remaining health risks from the source categories. If necessary, EPA may implement additional standards that address any significant remaining risk. EPA's published list now contains 175 categories of industrial and commercial sources that emit one or more toxic air pollutants.
In general, the difference between the two groups might be expressed in terms of concentration or quantity. The criteria pollutants are usually present in the atmosphere in much larger quantities than the TAPs. However, since both groups of pollutants can cause adverse health effects and environmental damage; the difference in the two groups is largely a matter of how they are regulated. That is, each group is subject to a different set of federal and state requirements.
The Criteria Pollutants are regulated under Title I of the Clean Air Act, which sets a national health standard for each pollutant. The burden is on the state to set up monitoring networks, monitor the air continuously for each pollutant, and report the data to EPA. States must also submit emission summaries and control plans for each pollutant, which demonstrate to EPA that state controls and regulations will both achieve and maintain the standard. Toxic Air Pollutants are regulated under Title III of the Clean Air Act. TAP regulations focus on the air emissions from targeted industries, and the control technology used to limit those emissions. In general, the burden is on industries to report emissions of TAPs, and to demonstrate to the state agency that the control technology in place meets MACT standards. In Louisiana, industries must also comply with the state regulation for toxic air pollutants.
There has long been concern with the possibility of a sudden and potentially catastrophic accident involving toxic chemicals. In 1984, an accidental release of highly toxic air pollutants in Bhopal, India, killed 3000 people and injured over 200,000 more. In response to this catastrophic event, Congress passed the Emergency Planning and Community Right-to-Know Act (EPCRA), which required major industrial plants to submit to EPA an annual inventory of all toxic chemicals released to air, water, and land. This list, known as the Toxic Release Inventory (TRI), is then made available to the public. The Clean Air Act also addresses the concern over toxic chemical accidents. In the 1990 CAA Amendments, Congress directed EPA to establish a program for the prevention of accidental releases of air toxics from industrial plants and created a Chemical Safety Board to investigate accidental releases of air toxics from industrial plants. States are now in the process of implementing the EPA regulations on chemical accident prevention.
What Is Louisiana Doing to Control and Reduce Toxic Air Pollutants?
Louisiana is one of the most heavily industrialized states in the nation, due largely to the attraction of the major waterway and deep-water port for shipping along the Lower Mississippi River Corridor. In 1987, the publication of the Toxic Release Inventory Report ranked Louisiana among the top five states in totals of toxic air emissions. Public concern over the high levels of toxic air releases prompted the State Legislature to enact Louisiana Revised Statute 30:2060 in 1989. Among other mandates, the law called for (1) the establishment of a "toxic air pollutant emission control program," (2) the development of a 1987 baseline for TAP emissions, and (3) the reduction of statewide TAP emissions by 50 percent from 1987 levels by December 31, 1996.
As mandated by the law, the Louisiana DEQ developed and promulgated the Comprehensive Toxic Air Pollutant Emission Control regulation, one of the most stringent state air toxics rules in the country. The state regulation also surpasses the federal regulation. In addition to incorporating the control technology (MACT) standards, the state rule establishes emission reporting requirements for all major sources of toxic air pollutants and sets an ambient air standard for each pollutant. The state list of regulated chemicals includes the federal toxic air pollutants and adds others which are of particular concern in Louisiana, such as ammonia and hydrogen sulfide.
Louisiana's current toxic air pollutant control program covers over 200 pollutants, and tracks toxic air emissions from over 250 industrial facilities. Under this program, facilities must report annual emission totals to DEQ's Toxic Emission Data Inventory. The goal of reducing statewide air toxic emissions by 50 percent from 1987 levels has been achieved. At the end of 1997, emissions of toxic air pollutants from all sources in the state were down by 60 percent (166,439,000 pounds) from 1987 levels. Toxic emissions are down across a broad spectrum of sources. For example, benzene emissions have decreased statewide by 58 percent, while hydrogen sulfide emissions are 83 percent lower than in 1987. This trend downward is expected to continue.
The state rule may be found in the Louisiana Administrative Code - LAC 33:III.Chapter 51; and it may be downloaded in Adobe Acrobat format from the Regulations Web Page.
Other Sources of Information on Toxic Air Pollutants
Some of the text used in this fact sheet was taken from EPA Brochure #451/K-98-001, dated February 1998. This document is available on EPA's web site. See Taking Toxics Out of the Air. For more information about toxic air pollutants, visit EPA's Unified Air Toxics Web Site.
Major industries must also report toxic releases (including releases to air, water, and land) to EPA's Toxic Release Inventory (TRI) under a separate law and environmental program. For more information on TRI, visit DEQ's TRI Page or EPA's TRI Page.