Indoor smoke from solid fuels: Assessing the environmental burden of disease
Environmental burden of disease series No. 4
Please note that evidence is currently being revised for this risk factor.
Assistance is no longer provided while evidence is being revised.
This guide outlines a method for estimating the disease burden at a national or local level caused by household exposures to indoor smoke from solid fuels. Solid fuel use is defined as the household combustion of coal or biomass (such as dung, charcoal, wood, or crop residues). Worldwide, approximately 50% of all households and 90% of rural households utilize solid fuels for cooking or heating. Solid fuels are commonly burned in inefficient simple stoves and in poorly ventilated conditions. In such situations, solid fuel use generates substantial emissions of many health-damaging pollutants, including respirable particulates and carbon monoxide, and results in indoor air pollution exposures often far exceeding national standards and international guidelines.
The disease burden from solid fuel use is most significant in populations with inadequate access to clean fuels, particularly poor households in rural areas of developing countries. Women and their youngest children are most exposed because of their household roles. Solid fuel use is most firmly associated with acute lower respiratory infections (including pneumonia) in young children, and chronic obstructive pulmonary disease and lung cancer in women (and to a lesser degree in men). Each of these three health outcomes is a major disease category in most societies and thus household solid fuel use is likely to be a major cause of disease burden in communities where it is prevalent. Globally, 2.6% of all ill-health is attributable to indoor smoke from solid fuels, nearly all in poor regions.
The approach described in this guide utilizes a binary classification scheme for exposure levels, separating the study population into those exposed to solid fuel use and those not exposed. This strategy enables the application of relative risks derived from a comprehensive review of the current epidemiological literature on solid fuel use. The guide presents ways to assess household fuel use, and discusses the evidence linking solid fuel use with major health outcomes. The combination of exposure levels and relative risks enables the calculation of disease burdens. Uncertainty in final results can be suggested through low-risk and high-risk scenarios. The guide closes with an illustrative case study for India.
The recommended methodology does not include all possible health outcomes suspected to be associated with solid fuel use, but just those for which the evidence is best. Annexes cover other important sources of indoor air pollution; studies linking solid fuel use with various other health outcomes; alternative approaches to determine the disease burden from solid fuel use; and sample fuel use survey questions.
Determining the impact of solid fuel use at national or local levels is important for identifying and prioritizing environmental and public health interventions. The two main intervention options focus on developing the physical and economic infrastructure to either encourage households to switch to cleaner fuels, or to employ improved stoves with chimneys or other means of reliable ventilation. In either case, education plays a vital role.