When the term “air pollution”
is uttered, it brings to mind
urban environments, replete
with car-packed freeways and belching
factories—not small villages and farmed
But rural areas are subject to local sources of pollution as well as secondary effects from urban areas—which means the total global health burden from air pollution falls largely on rural populations, said Kirk Smith, professor of environmental health sciences at UC Berkeley’s School of Public Health.
Smith recently discussed the issue before the United Nations Commission on Sustainable Development, which monitors progress toward goals set at the Earth Summit of the U.N. held in 1992. Air pollution was one of four subjects of focus at the Commission’s recent meetings, which also addressed energy, industrial development and climate change.
Addressing the Commission in May, Smith pointed out that in rural areas worldwide, where little monitoring is done for health assessments, there may be a significant understatement of the health impact of outdoor air pollution and the benefit of control. Emissions inventories done as part of climate and acid precipitation programs show clearly that rural areas can contribute substantially to total emissions. In some areas, such as China, total human exposure to outdoor air pollutants in rural areas may be up to 2.5 times the exposure that urban residents face.
“Although it is not possible yet to extrapolate globally,” said Smith, “it is clear that the WHO estimate of 800,000 premature deaths from urban air pollution is a substantial underestimate of the total annual impact of ambient air pollution from both urban and rural environments.”
People living in rural areas face health threats posed by three types of air pollution: that generated in the home by using simple, solid fuels for cooking and heat;“ambient” outdoor pollution from rural
and urban sources; and secondary pollutants, which form when atmospheric conditions trigger chemical reactions in air emissions.
Half the world’s households—mostly in rural areas in developing countries—use solid fuels, such as coal or biomass, for cooking and heating. (Biomass refers to any organic matter, such as wood or agricultural waste.)
The pollution caused by such fuels has well-established health effects: chronic obstructive pulmonary disease in adults and pneumonia in children, which together account for nearly 10% of all lost-life years worldwide, said Smith. In addition, lung cancer is clearly shown to result from coal use and possibly biomass smoke as well. Increasingly, studies are also linking solid fuel use to other cancers, as well as tuberculosis, cataracts, low birth weight and possibly heart disease.
Particularly in developing countries, where rural population density and the number of pollutant sources can exceed that in cities, outdoor air is significantly polluted—from surrounding cities, agricultural burning, and industrial facilities such as power plants and brick kilns.
The third source of pollution affecting rural areas results from the transport of emissions far from their primary emission point—even continents away—and their conversion into health hazards. Some emissions such as hydrocarbons in particular, that are themselves relatively harmless, are converted to hazardous ones by sunlight and interactions with other pollutants.
Many efforts to address air pollution have done little to alleviate its total impact. Installing chimneys to vent smoke from indoor stoves, for example, simply moves the pollution a few feet away, just adding to outdoor pollution. Moving industries from urban to rural areas similarly shifts the pollution from one environment to another. Future efforts to reduce the health eff ects of air pollution, Smith argued, should consider a pollutant’s total impact—in rural as well as urban areas.