Common and Hazardous Air Pollutants

America's Children and the Environment: Measures of Contaminants, Body Burdens, and Illnesses — U.S. Environmental Protection Agency— (Part 1: Environmental Contaminants / Outdoor Air Pollutants)         Particulate matter in the air (often called PM-10 or PM-2.5) has been found to cause increased risk of mortality (death), hospital admissions and emergency room visits for heart and lung diseases, respiratory effects, and decreases in lung function.       Prior to 1997, the National Ambient Air Quality Standard for particulate matter was based on particulate matter measuring 10 microns or less (PM-10). In 1997, the standard was revised to address the health risks from particulate matter measuring 2.5 microns or less (PM-2.5).       Lead accumulates in bones, blood, and soft tissues of the body. Exposure to lead can affect development of the central nervous system in young children, resulting in neurobehavioral effects such as lowered IQ.       Sulfur dioxide poses particular concerns for those with asthma, who are considered to be especially susceptible to its effects, which include respiratory illness, alterations in the lung's defenses and aggravation of cardiovascular diseases.         Exposure to carbon monoxide reduces the capacity of the blood to carry oxygen, thereby decreasing the supply of oxygen to tissues and organs such as the heart. Short-term exposure can cause neurobehavioral effects and a reduction in exercise performance.         Nitrogen dioxide effects include decreased lung function and increased respiratory symptoms or illness. Nitrogen dioxide is a major contributor to the formation of ground-level ozone, which can cause a variety of respiratory health effects and increased prevalence of asthma.         Hazardous air pollutants, also known as air toxics, have been associated with a number of adverse human health effects, including cancers, asthma and other respiratory ailments, and neurological problems such as learning disabilities and hyperactivity.         The Clean Air Act identifies 188 substances as hazardous air pollutants. Examples include benzene, trichloroethylene, mercury, chromium, and dioxin.         Hazardous pollutants are emitted from sources that are grouped into three general categories: major sources, area sources, and mobile sources.         Major sources typically are large industrial facilities such as chemical manufacturing plants, refineries, and waste incinerators. These sources may release air toxics during discharge through emission stacks or from equipment leaks.         Area sources typically are smaller stationary facilities such as dry cleaners. Collectively their emissions can be of concern — particularly where large numbers of sources are located in heavily populated areas.         Mobile sources include both on-road sources, such as cars, light trucks and buses, and non-road sources such as farm and construction equipment, marine engines, aircraft and locomotives.