Sick planet, sick people.

• Author: Chandra, Candace
• Position: Links between environmental decline and disease

About 25 percent of the global burden of disease and injury is linked to environmental decline, according to a recent U.N. World Health Organization report. Health and Environment in Sustainable Development was released in June, at the five-year anniversary of the Rio Earth Summit. A synthesis of earlier research, much of it by WHO officials, the report outlines the public health implications of pollution, deforestation, and other standard categories of environmental decline. But its definition of "environmental" is extended to cover aspects of life, such as indoor air quality, that generally get more attention from public health officials than from their environmental counterparts. The report reckons the "environmental contribution" to a disease by estimating the percentage of cases "that could be averted through feasible environmental interventions," such as pollution abatement, housing improvements, or water sanitation measures.

The resulting picture may be more striking in its details than in the overall 25 percent conclusion. Some of the most dangerous infectious diseases, for example, are largely driven by environmental pressures. Diarrheal diseases like cholera kill 3 million people every year; 90 percent of that toll results from contaminated water. Malaria claims 1.5 to 2.7 million lives a year, and 90 percent of these deaths can be linked to environmental trends as well - but usually through a complex of natural and social pressures. Mass colonization of rainforest, for example, often brings people into contact with large populations of mosquitoes that can spread the disease. Malaria-bearing mosquitoes frequently benefit from poorly planned development projects such as open-water irrigation schemes, too, or from rapid urbanization, that changes the drainage patterns of an area. Acute respiratory infections like pneumonia are 60 percent driven by environmental factors, primarily the burning of wood, coal, or other smoky fuels in the home. Of the 3 million deaths a year caused by air pollution...