The UER examines more than 15 sets of air quality data. Air pollution is composed of many environmental factors, such as carbon monoxide, nitrates, sulfur dioxide, ozone, lead, secondhand tobacco smoke and particulate matter. Air toxics, which are also known as hazardous air pollutants (HAPs), are those pollutants known or suspected to cause cancer or other serious health problems, or cause adverse environmental and ecological effects. They include pollutants like benzene, perchloroethylene, methylene chloride, heavy metals like mercury and lead, polychlorinated biphenyls (PCBs), dioxins, and some pesticides. More than half of the HAPs are known or suspected to be human carcinogens. In addition, many are known to affect the respiratory, neurological, immune, reproductive, or developmental systems, particularly for more susceptible or sensitive populations, such as children. HAPs are emitted from thousands of sources ranging from small commercial facilities to large industrial sources. HAPS also emanate from mobile sources such as motor vehicles – e.g., cars and trucks – and off-road equipment such as construction equipment and lawn mowers and their fuels.
A unique feature of urban areas is the proximity of many stationary and mobile sources and their pollutants to each other and to the people – estimated at 80% of the American population – that live or work in these areas. HAPs pose special threats in urban areas because of the cumulative effect of many toxic air pollutants upon large numbers of people from a variety of sources, such as cars, trucks, large factories, gasoline stations, and dry cleaners. Individually, some of these sources may not emit large amounts of toxic pollutants. However, all of these pollution sources combined can potentially pose significant health threats, particularly to sensitive subgroups such as children and the elderly. Also of concern is the impact of toxic emissions on minority and low-income communities, which are often located close to industrial and commercial urbanized areas. Thus, depending on exposure levels and characteristics of the pollutants, multiple pollutant exposure – often more prevalent in urban populations – may pose increased public health risks. The issue becomes even more complex when other population factors such as age, socio-economic status, proximity to emitting sources, decreased health and nutrition status, and lifestyles are considered because it is known that these factors may lead to increased sensitivity and susceptibility to the effects of HAP exposures.
While urban exposures to some pollutants may be fairly similar across the country, studies in a number of urban areas indicate that exposures and associated risks may vary significantly from one urban area to the next depending on the particular sources present (or dominant), the substances emitted, the local meteorology, and other factors.
Resources
U.S. Environmental Protection Agency (U.S. EPA)
http://www.epa.gov/
Partnership for Clean Fuels and Vehicles (PCFV)
http://www.sdp.gov/sdp/initiative/cei/29809.htm
World Health Organization
http://www.who.int/topics/air/
The American Lung Association
http://www.lungusa.org
AIRNow
http://airnow.gov/
Earth Justice
http://www.earthjustice.org/our_work/issues/air/
