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).
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 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.
