# **1. Introduction**

According to the WHO Global and Regional Burden of Disease Report, 2004 (http://www.who.int/publications/cra/en ), acute respiratory infections from indoor air pollution (IAP - pollution from burning wood, animal dung and other biofuels) are estimated to kill a million children annually in developing countries. These infections inflict a particularly heavy toll on poor families in South Asia and Africa. This has prompted the World Bank and other international development institutions to identify reduction of IAP as a critical objective for the coming decades (World Bank, 2001).

Although IAP is a complex mixture of small and large particles, recent epidemiological studies have reported that exposure to particulates, particularly small particulates, is strongly associated with respiratory illness and death. Small particles are likely to be more dangerous, since they can be inhaled deeply into the lungs and settle in areas where natural clearance mechanisms, like coughing, cannot remove them. The current scientific consensus is that most respiratory health damage comes from the inhalation of respirable particles whose diameter is less than 10 microns (PM10), with recent attention focusing on even finer particles (PM2.5).

The design of cost-effective IAP reduction strategies has been hindered by lack of information about actual PM concentrations in poor households. Data have been scarce because monitoring in village environments is difficult and costly. Relatively small-scale studies of indoor PM10 exposure from wood-fuel combustion have been conducted in Kenya (Boleij, et al., 1989, 36 households), Guatemala (Smith, et al., 1993, 60 households), Mexico (Santos-Burgoa, et al., 1998, 52 households), and Gambia (Campbell, 1997, 12 households), and indoor PM10 exposure from coal combustion has been conducted in Mongolia (Cowlin et al., 2005, 65 _gers_<sup>_1_</sup> ). In addition, Balakrishnan, et al., have studied a larger sample of houses in rural India (Balakrishnan, et al., 2002, 412 households; Parikh, et al., 2001, 436 households) and Baris et al. have studied a larger sample in China (Baris et al., 2006, 300 households). These studies have yielded two main conclusions: Natural gas and kerosene are far less pollution-intensive than biofuels such as wood and dung, and use of improved stove designs can significantly reduce indoor pollution from biofuels.

Unfortunately, nationwide energy surveys in many developing countries have revealed that poor households almost always use “dirty” biomass fuels, particularly in rural areas. This is often because clean fuels are not available. Even where a clean fuel is available, most poor households use dirty fuels because the relative price of the clean fuel is simply too high. Improved stoves for biomass combustion could help, but studies in Asia and Latin America have found almost no adoption of improved stoves, despite widespread promotional efforts. Households report non-adoption for a variety of reasons, including capital and maintenance costs, inconvenience, and incompatibility with food preparation traditions. Thus, neither clean fuels nor improved stoves offer strong prospects for reducing IAP in rural areas in the near future.

Some of the previous studies have alluded to construction materials, space configurations, cooking locations and household ventilation practices (use of doors and

> 1 Traditional Mongolian dwellings.

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