In terms of aggregate health effects, household solid fuel use is currently the most important source of indoor air pollution in developing countries. Although relatively equitable economic and rural development has contributed to reducing the use of solid fuels in some settings (e.g., in some newly industrialized Asian countries), indoor air pollution is likely to remain an important health risk in poorer developing countries in the absence of successful intervention programs. More broadly, indoor air quality issues in developing countries are dynamic phenomena that require dynamic research and policy responses.
One of the emerging issues in indoor air quality relates to the demographic, economic, and ecological changes of the past few decades. Some of the poorest households have been forced to use inferior sources of fuel (e.g., dung or crop residues instead of wood and charcoal). This is partially due to the rising price of fuels and because real income has remained unchanged or has even declined in some developing countries, especially in sub-Saharan Africa. The interactions of poverty, population, environment, and health, however, have complex characteristics that are dependent on local socioeconomic, geographical, and demographic factors. For example, if a stand of mature trees is cleared to open space for additional cultivation or grazing area, or for use in the lumber industry, the fallen trees are often burned in situ or processed into charcoal for sale in a distant town.
Households that formerly relied on fallen limbs and dead wood from that stand of trees find they must travel farther to meet their fuel-wood needs. If no mature stands with a sufficient stock of deadwood remain within a reasonable distance, poor households, unable to afford commercial fuels, may begin to cut smaller trees, which leads to a further loss of tree cover. If smaller trees are not an option, or prove insufficient to meet demand, then some households may turn to agricultural residues or animal manure. This shift has consequences that extend beyond the use of a lower quality and more polluting fuel. Crop residues are often used as fodder, and using traditional fodder as fuel can lower the value of a family’s livestock or lower the quality of the animals’ manure. When they are not used as fodder, crop residues are often left in the field as ground cover to protect topsoil between growing seasons. They may be ploughed back into the soil or burned on top of it before the next crop is planted; both activities return nutrients to the soil. Using these residues for fuel can leave topsoil unprotected between the harvest of one crop and the sowing of the next, leading to soil erosion and a loss of nutrients. Similarly, using animal manure as fuel takes away a valuable fertilizer, leading to lower yields or forcing the family to rely on expensive inorganic fertilizers. When coupled with increased malnutrition and exposure to other risks associated with poverty in these same households, the health effects of indoor air pollution would be greatly magnified. Therefore, while much of the literature has considered improvements in indoor air pollution as a result of economic development, the energy and health inequalities as a result of income inequality need particular attention.
Another emerging issue relates to urbanization and other forms of socio-demographic change, to changes in housing and neighborhood design, and to increased use of manufactured chemicals. The implications are that indoor air quality for some developing country households will be increasingly determined by pollution from sources other than their own energy use (nearby households, industries, transportation, insecticides, and chemical cleaners). Outdoor/indoor air quality interactions have been subject to research in industrialized countries. In developing countries, these issues should begin to appear on research and policy agendas, because many involve decisions that cannot be easily reversed.
Finally, smoking has been on the rise in developing countries over the past few decades. Environmental tobacco smoke, which has been subject to regulation in a number of industrialized countries, will increasingly affect the health of the many sectors of society in developing nations (e.g., workers in buildings where workplace smoking is allowed) and should receive early attention.
