Health Effects of Air Pollution

Transcription

1 Rising Energy Use: Health Effects of Air Pollution Outdoor Air and Health Urban Air: Health Effects of Particulates, Sulfur Dioxide, and Ozone Indoor Air: Still a Major Threat Biomass Use, While Declining, Will Remain High Burning Biomass Fuels Pollutes Indoor Air Outdoor Air and Health For more than a century, severe air pollution incidents in cities such as London have shown Smoke Pollution in Benzi, China. that breathing dirty air can be dangerous and, at times, deadly. In 1880, 2,200 Londoners died in one such incident when coal smoke from home heating and industry combined to form a toxic smog of sulfur dioxide gas and airborne combustion particles (240). But concern about the health effects of outdoor air pollution did not effectively coalesce until the late 1940s and early 1950s, when air pollution disasters on two continents raised an alarm. Both the 1948 "killer fog" in the small town of Denora, Pennsylvania, that killed 50, and the particularly virulent London "fog" of 1952, in which some 4,000 died, were associated with widespread use of dirty fuels and were catalysts for government efforts to tackle urban air pollution. Since then, many nations have adopted ambient air quality standards to safeguard the public against the most common and damaging pollutants. These include sulfur dioxide, suspended particulate matter, ground-level ozone, nitrogen dioxide, carbon monoxide, and lead all of which are tied directly or indirectly to the combustion of fossil fuels. Although substantial investments in pollution control in some industrialized countries have lowered the levels of these pollutants in many cities, poor air quality is still a major concern throughout the industrialized world. A recent assessment by the European Environment Agency found that 70 to 80 percent of 105 European cities surveyed exceeded WHO air quality standards (1 of 5) [8/29/ :57:20 AM]

2 for at least one pollutant (241). In the United States, an estimated 80 million people live in areas that do not meet U.S. air quality standards, which are roughly similar to WHO standards (242). Meanwhile, urban air pollution has worsened in most large cities in the developing world, a situation driven by population growth, industrialization, and increased vehicle use. Despite pollution control effects, air quality has approached the dangerous levels recorded in London in the 1950s in a number of megacities, such as Beijing, Delhi, Jakarta, and Mexico City (243). In these cities, pollutant levels sometimes exceed WHO air quality standards by a factor of three or more. In some of China's major cities, particulate levels are as much as six times the WHO guidelines (244). Worldwide, WHO estimates that as many as 1.4 billion urban residents breathe air exceeding the WHO air guidelines (245). The health consequences of exposure to dirty air are considerable. On a global basis, estimates of mortality due to outdoor air pollution run from around 200,000 to 570,000, representing about 0.4 to 1.1 percent of total annual deaths (246) (247). As the range of these estimates indicates, it is difficult to quantify the toll of outdoor air pollution. The health impacts of urban air pollution seem likely to be greater in some of the rapidly developing countries where pollution levels are higher. The World Bank has estimated that exposure to particulate levels exceeding the WHO health standard accounts for roughly 2 to 5 percent of all deaths in urban areas in the developing world (248). However, these mortality estimates alone do not capture the huge toll of illness and disability that exposure to air pollution brings at a global level. Health effects span a wide range of severity from coughing and bronchitis to heart disease and lung cancer. Vulnerable groups include infants, the elderly, and those suffering from chronic respiratory conditions including asthma, bronchitis, or emphysema. For example, air pollution in developing world cities is responsible for some 50 million cases per year of chronic coughing in children younger than 14 years of age (249). However, even healthy adults can suffer negative effects (250). (See Urban Air: Health Effects of Particulates, Sulfur Dioxide, and Ozone.) Many of air pollution's health effects, such as bronchitis, tightness in the chest, and wheezing, are acute, or short term, and can be reversed if air pollution exposures decline. Other effects appear to be chronic, such as lung cancer and cardiopulmonary disease. In fact, in the United States, two long-term epidemiological studies representing some of the most significant recent research on air pollution effects documented an increase in the death rate of those chronically exposed to dirty air. These studies, which compared death rates among many U.S. cities with widely varying pollution levels, found that mortality rates were 17 to 26 percent higher in cities with the dirtiest air compared with those with the cleanest air, and those with the dirtiest air had significantly higher rates of lung cancer and cardiopulmonary disease (251)(252). These increased risks translate roughly to a 1- to 2-year shorter life span for residents of the most polluted cities (253)(254). Higher infant mortality rates have also been associated with high particulate levels (255). Fewer studies have been done in developing countries, and those that have been done have relied on calculations of health impacts in developed countries. These calculations may not be directly transferable, however, given differences in pollutant exposures and baseline health (both nutrition and general health status may be lower in some developing countries) (256). Nonetheless, studies performed in developing countries suggest that urban air pollution may have a tremendous impact on health. For example, one recent analysis of Jakarta estimated that some 1,400 deaths, 49,000 emergency room visits, and 600,000 asthma attacks could be avoided each year if particulate levels were brought down to WHO standards (257). Meanwhile, in Latin America, exposure of some 81 million city residents more than one (2 of 5) [8/29/ :57:20 AM]

3 quarter of all city dwellers in the region o to high air pollution levels is believed to cause an estimated 65 million days of illness each year (258). Indoor Air: Still a Major Threat As dangerous as polluted outdoor air can be to health, indoor air pollution actually poses a greater health risk on a global level. Indoor air pollution is a concern in developed countries, where, for example, energy efficiency improvements sometimes make houses relatively airtight, reducing ventilation and raising indoor pollutant levels. In such circumstances, even small pollution sources -- emanating from a furnace, a new carpet, or from naturally occurring radon gas -- can lead to significant human exposures. Biomass Use, While Declining, Will Remain High Current and Projected Use of Biomass by Region, Selected Years By far the greatest threat of indoor pollution, however, still occurs in the developing countries, where some 3.5 billion people -- mostly in rural areas, but also in many cities -- continue to rely on traditional fuels for cooking and heating. (See Biomass Use, While Source: The World Bank, Rural Energy and Development: Improving Energy Supplies for Two Billion People (The World Bank, Washington, D.C., 1996), p. 26. Declining, Will Remain High.) Burning such fuels produces large amounts of smoke and other air pollutants in the confined space of the home a perfect recipe for high exposures. (Liquid and gaseous fuels such as kerosene and bottled gas, although not completely pollution-free, are many times less polluting than these unprocessed solid fuels.) In these circumstances, exposure to pollutants is often far higher indoors than outdoors. Indeed, the World Bank has designated indoor air pollution in developing countries as one of the four most critical global environmental problems (259). As the table "Burning Biomass Fuels Pollutes Indoor Air" shows, concentrations of indoor pollutants in households burning dirty fuels are excessive. These estimates must be viewed with some caution, however, because monitoring in developing countries has been limited. Daily averages often exceed current WHO guidelines by factors of 10, 20, or even more. Peak levels during cooking may exceed these levels by a further factor of five or so. Indeed, these data suggest that many tens of millions of people in developing countries routinely encounter pollution levels reached during the infamous London killer fog of 1952, leading to a huge estimated toll in disease and premature death. One researcher estimates that as many as 2.8 million deaths per year result from breathing elevated levels of indoor smoke from dirty fuels (i.e., in excess of the WHO particulate standard). This finding translates to about 6 percent of all deaths each year (260). If this kind of effect is confirmed, indoor air pollution would be (3 of 5) [8/29/ :57:20 AM]

4 one of the largest single risk factors for ill health in the world. Epidemiological studies in developing countries have linked exposure to indoor air pollution from dirty fuels with at least four major categories of illness: acute respiratory infections (ARI) in children; chronic obstructive lung diseases such as asthma and chronic bronchitis; lung cancer; and stillbirths and other problems at birth. Of these, ARI appears to have the greatest health impact in terms of the number of people affected and the time lost due to illness, especially in children younger than age 5. Studies in a number of different countries and settings have examined the link between exposure to smoke from cookstoves with the development of ARI in children. In South Africa, investigators found that Zulu children living in homes with woodstoves were almost five times more likely to develop a respiratory infection severe enough to require hospitalization (261). In Nepal, researchers observed a significant relationship between the number of hours spent near the fire and the incidence of moderate and severe cases among 2-year-olds (262). Likewise, a recent study in the Gambia found that children carried on their mother's backs as they cooked over smoky cookstoves contracted pneumococcal infections one of the most serious kinds of respiratory infections at a rate 2.5 times higher than nonexposed children (263). Burning Biomass Fuels Pollutes Indoor Air Indoor Particulate Concentrations from Biomass Combustion in Developing Countries REGION NUMBER OF STUDIES DURATION MICROGRAMS PER CUBIC METER Pacific 2 12 h 1,300-5,200 South Asia 15 Cooking period 850-4,400 a Cooking Non-cooking 880 a 24 h 2,000-2,800 a Various 2,000-6,800 Urban Infants, 24 h a China 8 Various 2,600-2,900 Various 1,100-11,000 a Africa 8 Cooking/heating 800-1,700 Cooking/heating 24 h Urban area, 24 h 1,300 a 1,300-2,100 a a Latin America 5 Cooking/heating 24 h 440-1,100 a 720-1,200 a Source: Adapted from World Health Organization (WHO), Health and Environment in Sustainable Development: Five Years After the Earth Summit (WHO, Geneva, 1997), Table 4.4, p. 87. Many respiratory infections in the developing world result in death, and evidence shows that exposure to cookstove smoke may contribute to higher mortality rates. For example, a study in Tanzania found that children younger than 5 years of age who died of ARI were 2.8 times more likely to have been sleeping in a room with an open cookstove than healthy children (264). Overall, studies indicate that exposure to wood smoke from cook fires in poorly ventilated conditions may increase the risk of a young child contracting a serious respiratory infection from two to six times. Adults suffer the ill effects of severe indoor pollution as well. Several studies found strong links between (4 of 5) [8/29/ :57:20 AM]

5 chronic lung diseases in women and exposure to smoke from open cookstoves (265)(266). One recent Colombian study found women exposed to smoke during cooking were more than three times more likely to suffer chronic lung disease (267). Other studies suggest that this risk increases in response to the years of exposure to smoke. A study in Mexico showed that women who had been exposed to wood smoke for many years faced 75 times more risk of acquiring chronic lung disease than unexposed women about the level of risk that heavy cigarette smokers face (268). Lung cancer, too, is associated with high levels of smoke especially coal smoke, which contains a plethora of carcinogenic compounds. Most studies of coal-smoke exposures have been conducted in China, where residential use of coal is still common (269). More than 20 studies suggest that urban women who use coal for cooking and heating over many years are subject to a risk of lung cancer two to six times higher than women who use gas. Rural coal-smoke exposures, which tend to be higher, seem to increase lung cancer risks by a factor of nine or more (270). Exposure to high indoor smoke levels has also been linked with pregnancy-related problems like stillbirths and low birth weight. One study in western India found a 50-percent increase in stillbirths associated with the exposure of pregnant women to indoor smoke (271). Indoor air pollution most likely contributes to excess heart disease in developing countries as well. In developed countries, outdoor pollution at levels far below those found in smoky indoor environments has been linked with heart disease. When it happens, the well-documented transition up the energy ladder from dirty to clean fuel will greatly reduce the threat from indoor air pollution in developing countries. The speed of this transition will depend on several factors, including energy prices, trends in personal income, and national policies targeting the indoor air problem. Continued low oil prices and strong government action promoting cleaner stoves and cleaner fuels such as kerosene or gas could result in a much faster transition, but these favorable conditions are far from assured. In fact, even though investments in cleaning up indoor air can be very cost-efficient in terms of health, nations have historically spent little on the indoor air problem. World Resource Institute, 10 G Street, NE (Suite 800), Washington, DC (202/ ; fax: 202/ ). For more information contact gregm@wri.org. (5 of 5) [8/29/ :57:20 AM]

6 Health Effects of Air Pollution: Urban Air: Health Effects of Particulates, Sulfur Dioxide, and Ozone Of the suite of pollutants that taint urban air, fine suspended particulate matter, sulfur dioxide (SO2 ), and ozone pose the most widespread and acute risks; however, airborne lead pollution is a critical concern in many cities as well. Recent studies on the effects of chronic exposure to air pollution have singled out particulate matter as the pollutant most responsible for the life-shortening effect of dirty air, although other pollutants may also play an important role. Particulate Pollution Suspended particulate matter is a nearly Smoke Pollution in Benzi, China. ubiquitous urban pollutant. Although particulate levels in North America and Western Europe rarely exceed 50 micrograms of particulate matter per cubic meter (µg/m 3 ) of air, levels in many Central and Eastern European cities and in many developing nations are much higher, often exceeding 100 µg/m 3 (1). Particulate air pollution is a complex mixture of small and large particles of varying origin and chemical composition. Larger particles, ranging from about 2.5 microns to 100 microns in diameter, usually comprise smoke and dust from industrial processes, agriculture, construction, and road traffic, as well as plant pollen and other natural sources. Smaller particles those less than 2.5 microns in diameter generally come from combustion of fossil fuels. These particles include soot from vehicle exhaust, which is often coated with various chemical contaminants or metals, and fine sulfate and nitrate aerosols that form when (1 of 4) [8/29/ :57:49 AM]

7 SO2 and nitrogen oxides condense in the atmosphere. The largest source of fine particles is coal-fired power plants, but auto and diesel exhaust are also prime contributors, especially along busy transportation corridors. The health effects of particulates are strongly linked to particle size. Small particles, such as those from fossil fuel combustion, are likely to be most dangerous, because they can be inhaled deeply into the lungs, settling in areas where the body's natural clearance mechanisms can't remove them. The constituents in small particulates also tend to be more chemically active and may be acidic as well and therefore more damaging (2). Numerous studies associate particulate pollution with acute changes in lung function and respiratory illness (3)(4), resulting in increased hospital admissions for respiratory disease and heart disease, school and job absences from respiratory infections, or aggravation of chronic conditions such as asthma and bronchitis (5)(6). But the more demonstrative and sometimes controversial evidence comes from a number of recent epidemiological studies. Many of these studies have linked short-term increases in particulate levels, such as the ones that occur during pollution episodes, with immediate (within 24 hours) increases in mortality. This pollution-induced spike in the death rate ranges from 2 to 8 percent for every 50-µg/m 3 increase in particulate levels. These basic findings have been replicated on several continents, in cities as widely divergent as Athens, São Paulo, Beijing, and Philadelphia (7)(8)(9). During major pollution events, such as those involving a 200-µg increase in particulate levels, an expert panel at the World Health Organization (WHO) estimated that daily mortality rates could increase as much as 20 percent (10). These estimates should be viewed with caution, however, because some of those who die during a pollution episode were already sick, and the pollution may have hastened the death by only a few days. In the aggregate, pollution-related effects like these can have a significant impact on community health. WHO has identified particulate pollution as one of the most important contributors to ill health within Europe. In those cities where data on particulates were available, WHO estimated that short-term pollution episodes accounted for 7 to 10 percent of all lower respiratory illnesses in children, with the number rising to 21 percent in the most polluted cities. Furthermore, 0.6 to 1.6 percent of deaths were attributable to short-term pollution events, climbing to 3.4 percent in the cities with the dirtiest air (11). Nor are health effects restricted to occasional episodes when pollutant levels are particularly high. Numerous studies suggest that health effects can occur at particulate levels that are at or below the levels permitted under national and international air quality standards. In fact, according to the WHO and other organizations, no evidence so far shows there is a threshold below which particle pollution does not induce some adverse health effects, especially for the more susceptible populations (12)(13). This situation has prompted a vigorous debate about whether current air quality standards are sufficient to protect public health. Sulfur Dioxide SO2 is emitted largely from burning coal, high-sulfur oil, and diesel fuel. Because this gas is usually found in association with particulate pollution as SO2 is the precursor for fine sulfate particles separating the health effects of these two pollutants is difficult. Together, SO2 and particulates make up a major portion of the pollutant load in many cities, acting both separately and in concert to damage health. (2 of 4) [8/29/ :57:49 AM]

8 Although ambient concentrations of SO2 have declined in many cities in Western Europe and North America, they remain higher often by a factor of 5 to 10 in a number of cities in Eastern Europe, Asia, and South America, where residential or industrial coal use is still prevalent and diesel traffic is heavy (14). SO2 affects people quickly, usually within the first few minutes of exposure. Epidemioloogical studies indicate that SO2 exposure can lead to the kind of acute health effects typical of particulate pollution. Exposure is linked to an increase in hospitalizations and deaths from respiratory and cardiovascular causes, especially among asthmatics and those with preexisting respiratory diseases (15)(16)(17)(18). The severity of these effects increases with rising SO2 levels, and exercise enhances the severity by increasing the volume of SO2 inhaled and allowing SO2 to penetrate deeper into the respiratory tract (19). Asthmatics may experience wheezing and other symptoms at much lower SO2 levels than those without asthma. When ozone pollution is also present, asthmatics become even more sensitive to SO2 a good reminder that air pollutants generally do not occur in isolation, but in complex mixtures that create the potential for synergistic effects among pollutants (20)(21). Ozone Ground-level ozone is the major component of the photochemical smog that blankets many urban areas. It is not emitted directly but is formed when nitrogen oxides from fuel combustion react with so-called volatile organic compounds (VOCs) such as unburned gasoline or paint solvents in the atmosphere. sunlight and heat stimulate ozone formation, so peak ozone levels generally occur in the summer. Ozone pollution has become widespread in cities in Europe, North America, and Japan as auto and industrial emissions have increased. Many cities in developing countries also suffer from high ozone levels, although few monitoring data exist (22)(23). A powerful oxidant, ozone can react with nearly any biological tissue. Breathing ozone concentrations of ppm levels typical in many cities can irritate the respiratory tract and impair lung function, causing coughing, shortness of breath, and chest pain. Exercise increases these effects, and heavy exercise can bring on symptoms even at low ozone levels (0.08 ppm). Evidence also suggests ozone exposure lowers the body's defenses, increasing susceptibility to respiratory infections (24)(25). As ozone levels rise, hospital admissions and emergency room visits for respiratory illnesses such as asthma also increase. On average, studies show that hospital admissions rise roughly 7 to 10 percent for a 0.05 ppm increase in ozone levels. In its recent analysis of ozone health impacts in 13 cities where ozone levels exceeded U.S. air standards, the American Lung Association estimated that high ozone levels were responsible for approximately 10,000 to 15,000 extra hospital admissions and 30,000 to 50,000 additional emergency room visits during the ozone season (26)(27). References and Notes 1. World Health Organization (WHO), Update and Revision of the Air Quality Guidelines for Europe, WHO Regional Office for Europe, Report No. EUR/ICP/EHAZ 94-05/PB01 (WHO, Copenhagen, 1994), p Ibid., p Douglas Dockery et al., "Health Effects of Acid Aerosols on North American Children: Respiratory Symptoms," Environmental Health Perspectives, Vol. 104, No. 5 (1996), p U.S. Environmental Protection Agency (USEPA), Office of Air Quality Planning and Standards, Review of National (3 of 4) [8/29/ :57:49 AM]

9 Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information, Report No. EPA-452/R (USEPA, Washington, D.C., 1996), pp. V-2-V-24, V-27-V-28, V Deborah Shprentz, Breathtaking: Premature Mortality Due to Particulate Air Pollution in 239 American Cities (Natural Resources Defense Council, New York, 1996), p Op. cit. 4, pp. V-20-V Op. cit. 4, pp. V-11 to V Bart Ostro, "The Association of Air Pollution and Mortality: Examining the Case for Inference," Archives of Environmental Health, Vol. 48, No. 5 (1993), p Health Effects Institute (HEI), Particulate Air Pollution and Daily Mortality: Replication and Validation of Selected Studies (HEI, Cambridge, MA, 1995), p Op. cit. 4, pp. v R. Bertollini et al., Environment and Health 1: Overview and Main European Issues, WHO Regional Publications, European Series, No. 68 (World Health Organization, Copenhagen, 1996), pp Op. cit. 1, p Op. cit. 5, p Op. cit. 1, p A. Peters et al., "Acute Effects of Exposure to High Levels of Air Pollution in Eastern Europe," American Journal of Epidemiology, Vol. 144, No. 6 (1996), pp. 570, J. Sunyer et al.,"air Pollution and Mortality in Barcelona," Journal of Epidemiology and Community Health, Vol. 50 (Supplement 1) (April 1996), p. S M. Vigotti et al., "Short-Term Effects of Urban Air Pollution on Respiratory Health in Milan, Italy, ," Journal of Epidemiology and Community Health, Vol. 50 (Supplement 1) (April 1996), p. S G. Touloumi, E. Samoli, and K. Katsouyanni, "Daily Mortality and 'Winter type' Air Pollution In Athens, Greece: A Time Series Analysis Within the APHEA Project," Journal of Epidemiology and Community Health, Vol. 50 (Supplement 1) (April 1996), p. S Op. cit. 1, p Lawrence Folinsbee, "Human Health Effects of Air Pollution," Environmental Health Perspectives, Vol. 100 (1992), pp Derek Elsom, Smog Alert: Managing Urban Air Quality (Earthscan Publications Limited, London, 1996), p Op. cit. 1, p World Health Organization and the United Nations Environment Programme, Urban Air Pollution in Megacities of the World (Blackwell Publishers, Oxford, UK, 1992), pp Halûk Özkaynak et al., Ambient Ozone Exposure and Emergency Hospital Admissions and Emergency Room Visits for Respiratory Problems in 13 U.S. Cities (American Lung Association, Washington, D.C., 1996), pp Op. cit. 4, pp , Op. cit. 24, pp Op. cit. 4, pp. 24, 46-51, 61. World Resource Institute, 10 G Street, NE (Suite 800), Washington, DC (202/ ; fax: 202/ ). For more information contact gregm@wri.org. (4 of 4) [8/29/ :57:49 AM]