Air Pollution And Urban Smog

Air pollution is not a new problem, nor is it only recently recognized to be a problem. Concern about coal smoke in the city motivated the appointment of a commission to study its effects in 13th-century London (Oppenheimer & Boyle, 1990). The Industrial Revolution and the rise of industrial cities helped make the problem the global one that, like the problems of atmospheric warming and acid rain, it is today. Although the problem is not new, knowledge of the details of air pollutants has increased dramatically in recent years; 189 chemicals are identified as hazardous air pollutants in the U.S. Clean Air Act Amendments of 1990 (Kelly, Mukund, Spicer, & Pollack, 1994).

Although it can have complicated effects on natural processes such as the suppression of precipitation (Rosenfeld, 2000), air pollution is of concern primarily because of its implications for health. The adverse health effects of air pollution, especially in the form of sulfur and nitrogen oxides and lead, are well documented (Lave & Seskin, 1977; National Research Council, 1977c, 1978a, 1978b, 1980; Shriner, Richmond, & Lindberg, 1980). The relatively high concentrations of atmospheric pollutants like carbon monoxide in the blood of people living in industrialized societies is believed to be attributable to—in addition to cigarette smoking—emissions from motor vehicles, industrial processes, and home heating and cooking facilities (Goldsmith & Landow, 1968). It has been estimated that, as of 1987, the United States was spending $16 billion annually on health care costs associated with air pollution, and that it incurs $40 billion of costs in decreased worker productivity and about $7 billion as a consequence of damage to buildings, monuments, and other materials (Mitchell, 1987). The annual economic value of avoiding the health effects of tropospheric ozone and airborne particulate matter was estimated, as of 1992, to be about $ 10 billion in the South Coast Air Basin of California alone (Hall et al., 1992).

Evidence suggests that, in addition to having an impact on physical health, poor air quality can also produce detrimental effects on psychological stability (Strahilevitz, Strahilevitz, & Miller, 1979). There has been some speculation that some motor vehicle accidents may be due, at least partially, to impaired driver performance resulting from driver exposure to air pollutants such as carbon monoxide (Ury, 1968).

Air quality standards in the United States are high compared with those of many industrialized countries, and considerable progress has been made in recent years to reduce concentrations of several of the major pollutants, including lead, sulfur dioxide, nitrogen dioxide, and particulates. Greatly reduced levels of lead in the blood of U.S. children have been attributed to the elimination of lead from gasoline production (Thomas & Spiro, 1994). Ozone and carbon monoxide continue to be serious problems, however; perhaps a third or more of the U.S. population lives in areas that do not meet government standards with respect to one or the other, or both, of these pollutants (Environmental Protection Agency, 1992; Gray & Alson, 1989; National Research Council, 1991; Office of Technology Assessment, 1988; Suhrbier & Deakin, 1988).

Efforts to decrease ozone concentrations in the troposphere have been directed primarily at the reduction of emissions of volatile organic compounds (VOCs) and oxides of nitrogen, which react under certain atmospheric conditions to produce ozone (Finlayson-Pitts & Pitts, 1997; National Research Council, 1991; Stone, 1992). Government regulations aimed at reducing tropospheric ozone have been somewhat effective, but less so than intended and anticipated. One problem seems to have been underestimation of the amount of critical emissions. Emission estimates are based in part on measurements and in part on models of how emission sources (e.g., traffic) are distributed in space and time, so estimates can only be as good as the models are accurate (Seinfeld, 1989). More generally, the problem of determining the contribution of vehicle emissions to air pollution and the effectiveness of various possible methods for decreasing it are not well understood (Calvert, Heywood, Sawyer, & Seinfeld, 1993). Decreasing ozone by controlling VOC emissions is complicated because relative reactivity—ozone-forming potential—can differ by more than an order of magnitude from one compound to another, and such differences have not been reflected in emission regulations (Russell et al., 1995).

Another problem relating to tropospheric ozone management is uncertainty regarding what constitutes a harmful level of concentration. On the basis of medical and epidemiological data showing that prolonged exposure to moderately high concentrations can have deleterious health effects, the Environmental Protection Agency (EPA) has proposed a new and more stringent National Ambient Air Quality Standard. Many of the rural areas that are in compliance with the existing standard would be out of compliance with the new one (Chameides, Saylor, & Cowling, 1997).

The situation is much worse in many areas of the world than it is in the United States. Eastern Europe and parts of the former Soviet Union have severe air pollution problems largely because of uncontrolled use of high-sulfur fuels in heavy industry (Chandler, Makarov, & Dadi, 1990). One estimate has more than 70 million people there being exposed to at least five times the official pollution limits (Wirl, 1991). According to another estimate, 88 Soviet cities with a combined population of 42 million people had toxic air pollution levels 10 times the "maximum permissible" as of 1989 (Chandler, Makarov, & Dadi, 1990). The environmental implications of the recent political upheavals in this part of the world are unclear (Khabibullov, 1991).

Most of the concern about air quality has been focused on the problem of industrial and automotive emissions and their effects on outdoor air in and around urban areas. Less attention has been paid to other sources of air pollution and to the problem of indoor air quality. The problem is not negligible. There is evidence to suggest that people are likely to have their greatest contact with toxic substances in homes, offices, or automobiles (Ott & Roberts, 1998; Wallace, 1995). The main sources of indoor air pollution, according to Ott and Roberts, include, in addition to cigarette smoke, "moth repellents, pesticides, solvents, deodorizers, cleansers, dry-cleaned clothes, dusty carpets, paint, particle board, adhesives, and fumes from cooking and heating" (p. 91). The toxic substances in these products include polycyclic aromatic hydrocarbons (compounds produced by incomplete combustion), carbon monoxide (also formed from incomplete combustion), paradichlorobenzene (found in moth repellents, toilet disinfectants, and deodorizers), and chloroform (formed from heated water that has been chlorinated). In much of the world, especially in developing countries, indoor air is often polluted by injurious smoke from fuels traditionally used for cooking and water heating (Holdren, 1990). The effect of tobacco smoke on nonsmokers in buildings has been an increasing concern in the United States (Eriksen, LeMaistre, & Newell, 1988; Fielding & Phenow, 1988), and some attention is being given to the problem of poor air quality in office buildings more generally (Mendell & Smith, 1990).

Apparently air quality can be poor without people being keenly aware of it. People who live in areas of high pollution are considerably less likely to acknowledge air pollution as a problem if indirectly queried about it, by being asked, for example, to list the five most serious problems in their community, than if asked about the presence of air pollution explicitly (Creer, Gray, & Treshow, 1970; Rankin, 1969). The relative insensitivity to this problem may be due in part to the fact that some major pollutants (e.g., carbon monoxide) are odorless and colorless, so their presence is not perceptible directly. Accommodation may also help account for it; people who live continuously in polluted areas may come to view the prevailing situation as normal (Evans, Jacobs, & Frager, 1982a, 1982b).

The problem of air pollution is closely linked with that of soil and water contamination because air pollutants fall to the ground as particulate matter or as solutes in precipitation. Many of the chemicals used for industrial and agricultural purposes (e.g., polychlorinated biphenyls [PCBs] and pesticides) are transported by the atmosphere to areas far removed from where they were used and can have a variety of effects, some long-lasting and cumulative, on soil and groundwater supplies. PCBs are artificial, stable compounds used in the manufacture of a variety of consumer products. Because of their chemical stability, they accumulate over time—among other places, in the food chain. Their effect on animal and human health is a matter of debate and has stimulated considerable political controversy (Stix, 1998).

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