Outdoor air and health
For more than a century, severe air pollution incidents in cities such as London have shown 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 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 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
|Biomass use, while declining, will remain high|
|Current and Projected Use of Biomass by Region, Selected Years|
|Source: The World Bank, Rural Energy and Development: Improving Energy Supplies for Two Billion People (The World Bank, Washington, D.C., 1996), p. 26.
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.