Modeling household solid fuel use towards reporting of the Millennium Development Goal indicator Sumi Mehta Health Effects Institute, 120 Second Avenue, Boston, MA 02129, USA E-mail: smehta@healtheffects.org Fiona Gore, Annette Prüss-stün, and Eva Rehfuess Protection of the Human Environment, World Health Organization (WHO), 20, Avenue Appia CH-1211 Geneva 27, Switzerland Kirk Smith Environmental Health Sciences, University of California, Berkeley CA 94720, USA Household use of solid fuels, such as dung, wood, agricultural residues, charcoal, and coal, is likely to be the largest indoor source of air pollution in developing countries. Combustion of solid fuels in inefficient stoves under poor ventilation conditions can result in large exposure burdens, par- ticularly for women and young children, who spend the major part of their time at home. The importance of this public health and environmental issue is reflected in the inclusion of the per- centage of households using solid fuels as an indicator towards the achievement of the Millennium Development Goal (MDG) for environmental sustainability. This article outlines the model used for completing missing country data for household use of solid fuels. Out of a total of 181 country data points reported, data were available for 94 countries. These included estimates from 42 coun- tries where household solid fuel use was previously unknown, largely from the recently conducted World Health Survey. Based on the data available for these countries, using step-wise regression, a model to predict household solid fuel use based on rural population, gross national income (GNI) and geographic regional variables was developed. Thirty-five data points were estimated using this model. In general, household solid fuel use seems to be lower in 2003 than in 2000. Yet, even with increases in economic development and urbanization, drastic reductions in household solid fuel use are unlikely to occur in the absence of targeted programs to promote cleaner fuels. 1. Background Cooking and heating with solid fuels, such as dung, wood, agricultural residues, charcoal, and coal, is likely to be the largest indoor source of air pollution in developing countries. Combustion of solid fuels in inefficient stoves under poor ventilation conditions can result in large ex- posure burdens, particularly for women and young chil- dren, who spend the major part of their time at home. Because there is relatively little information on the in- door concentrations or exposures of these pollutants from solid fuel use, or on the baseline concentrations within similarly constructed households not using solid fuels, epidemiological evidence on the health effects of solid fuel use is based mainly on binary classifications of ex- posure, for example whether solid fuels were used for cooking or heating. Similarly, in the absence of detailed information on exposure to indoor air pollution from solid fuel use at the national level, binary classifications of household solid fuel use are used as a practical surrogate for exposure to indoor air pollution for burden of disease estimation, as well as to indicate progress towards the at- tainment of the Millennium Development Goal (MDG) for environmental sustainability. In cases where data coverage is low or non-existent, it is necessary to predict solid fuel use. Previous estimates modeled missing country data for 2000 when survey data were available for only 52 countries [Smith et al., 2004]. This paper presents modeled estimates of household solid fuel use for countries where solid fuel use was unknown in 2003, now based on known data of 94 countries, in- cluding data from the recently conducted World Health Survey. 2. Data and methods 2.1. Available data on household solid fuel use at the national level In many countries where large proportions of the popula- tion cook with solid fuels, household energy data are Energy for Sustainable Development ! Volume X No. 3 ! September 2006 Articles 36