Cooking catastrophe: chronic exposure to burning biomass. (Science Selections).

With about half of the world's population relying on biomass fuels (wood, agricultural residues, and charcoal) as the primary source of household energy, research attention is increasingly focusing on this cause of indoor air pollution. In India, 5-6% of the nation's burden of disease has been estimated to be attributable to biomass combustion. Although biomass burning is clearly a major health risk factor, few quantitative exposure assessments have been performed in India to help clarify the exposure-response relationship. Now, a team of Indian researchers led by Kalpana Balakrishnan from the Sri Ramachandra Medical College and Research Institute (Deemed University) have assessed and quantified exposures to respirable combustion products in 436 rural households in the southern Indian state ofTamil Nadu [EHP 110:1069-1075].

Exposure to the respirable particles and gases generated by the combustion of biomass fuels has been linked in several studies to adverse health effects such as chronic bronchitis and acute respiratory infections in Children. Although a few studies similar to this one have been conducted previously in northern India, none have been done in the south, where the climate and culture are very different, resulting in patterns and concentrations of exposure at variance with data obtained in the north.

Biomass fuels are seldom used for heating in the warmer southern regions, but are widely used for both indoor and outdoor cooking. About 90% of the households studied used only biomass fuels, and even among the households that used comparatively clean fuels such as kerosene, 95% used biomass fuels to cook at least one meal a day. In addition, say the authors, women's movements are less restricted in the south--unlike in northern India, women in the south do not cover their faces and usually may move outside the house even in the presence of men, factors that could substantially reduce exposures.

To assess a variety of potential exposures to particulates generated by biomass combustion, the researchers sampled both indoor and outdoor air during cooking and noncooking times, and had women who were cooking wear a personal air sampler during meal preparation. In addition, all adult household members (women cooks, women assisting with cooking, women not involved with cooking, men who stayed at home, and men who worked outside the home) kept time-activity records. The team also gathered information about other exposure covariants such as fuel type, whether the kitchen was inside (with or without a partition) or outside (attached or nonattached), number of meals cooked, cooking duration, and time spent in or near the kitchen during cooking.

The investigators used the personal air sampler and time-activity record data to determine exposures for all household adults over a 24-hour period. They found that fuel type, type and location of kitchen, and time spent near the kitchen while cooking were the most important determinants of exposure, with the women cooks, as would be expected, encountering the highest average exposures. Their data also showed that living area concentrations were often greater than kitchen concentrations in households with partitionless kitchens, presumably because the increasing distance from the stove allowed for greater dispersal of particulates. This puts the elderly and young children, who are likely to be indoors during cooking times, at high risk of adverse effects from exposure.

The authors suggest that this baseline exposure information will help lay the framework for the creation of a regional exposure database, which would be useful in future studies of the exposure-response relationship in indoor air pollution in India and other developing countries.