"Because people spend a high percentage of their time indoors, and concentrations of pollutants often are higher in indoor air than outdoors, the human health risks indoors generally can be greater relative to risks from exposure to pollutants in the ambient (i.e., outdoor) air. In 1987, indoor air quality was identified by EPA [U.S. Environmental Protection Agency] scientists as one of the greatest sources of environmental risk to human health. EPA's Science Advisory Board, an independent body of experts, reviewed and endorsed this comparative risk ranking and in 1990 called upon the agency to give a higher priority to funding such high-risk environmental problems. In 1997, the Presidential and Congressional Commission on Risk Assessment and Risk Management again considered the relative risks presented by various environmental problems and concluded that indoor pollution could pose a substantial public health risk. In 2011, a report by the Institute of Medicine warned that many indoor air quality problems might get worse if adaptations to climate change are made without better information and programs aimed at pollution prevention. For example, methods to make homes better insulated and more energy efficient may result in less circulation with outdoor air, potentially increasing indoor concentrations of pollutants unless effective filtration or treatment technologies can be incorporated. This report describes common indoor pollutants, discusses federal statutes that have been used to address indoor pollution, and analyzes key issues surrounding some general policy options for federal policy makers. The focus is on indoor chemical contaminants, rather than on temperature, humidity, or pollution from animals, fungal or bacterial organisms, or plant pests."
CRS Report for Congress, R42620