Summary: Officials at the Environmental Protection Agency (EPA) and others have long cited indoor pollution as one of the most serious environmental risks to public health. Indoor pollutants range from natural sources, such as radon gas, to commonly used consumer products, such as cleaners and solvents, to various household activities, such as cooking or smoking. Concentrations of pollutants in indoor air can exceed those found outside by a factor of two to five. Moreover, some vulnerable groups, such as the very young and the infirm elderly, spend as much as 90 percent of their time inside. Federal agencies report that they spent nearly $1.1 billion on indoor pollution research from 1987 through 1999. Research by the federal government and others has led to notable progress in understanding indoor pollution and in devising ways to mitigate the problem. Consumer products have been reformulated, and building materials and practices have been changed. However, many gaps in understanding the problem remain, including uncertainties about (1) the identity and the sources of pollutants; (2) the mechanisms by which people are exposed to them; (3) the health effects resulting from prolonged and intermittent exposure to low-level concentrations of chemical and biological pollutants as well as complex pollutant mixtures; and (4) the most cost-effective strategies for reducing pollutant sources, exposures, and consequent health effects.
