This chapter summarizes the methodology used to assess the burden of disease caused by indoor air pollution from household use of solid fuels.  Most research into and control of indoor air pollution worldwide has focused on sources of particular concern in developed countries, such as environmental tobacco smoke (ETS), volatile organic compounds from furnishings and radon from soil.  Although these pollutants have impacts on health, little is known about their global distribution.  Thus, we focus solely on indoor smoke from household use of solid fuels, the most widespread traditional sources of indoor air pollution on a global scale.

In order to be consistent with the epidemiological literature, binary classifications of household use of solid fuels (biomass and coal) were used as a practical surrogate for actual exposure to indoor air pollution.  Specifically, household solid fuel use was estimated at the national level using binary classifications of exposure to household fuel use, i.e. solid fuel and non-solid fuel (gas, kerosene, electricity).  We estimated exposure to smoke from solid fuel by combining a number of national surveys of household fuel use into a regression model that predicts use accordant to independent, development-related variables, such as income and urbanization.  Although this method was necessary owing to the current paucity of quantitative data on exposure, we acknowledge that it overlooks the large variability of exposure within households using solid fuels.  As pollution emissions from the use of solid fuel may not always indicate high exposures, we have adjusted exposure estimates by a second term, the ventilation factor, which is based on quantitative measures of ventilation.

Estimates of relative risk obtained from epidemiological studies were combined in meta-analyses for three disease end-points for which there is strong evidence of an association with use of solid fuels: acute lower respiratory infections (ALRI) in children aged more than five years, chronic obstructive pulmonary disease (COPD) and lung cancer (estimates for lung cancer are only for use of coal).