In projects that include lead as a component of indoor air, ingestion of lead-based paint is a serious concern, particularly for special populations, such as children and residents of older homes. After radon and ETS, the next highest cancer risks in indoor air are attributed to volatile organic compounds, especially formaldehyde. Projects report a great deal of uncertainty in these estimates, and reflect this in much greater ranges of estimated risk. Asbestos was included for analysis by many projects, possibly because of lingering public concern, but reports typically concluded asbestos carried relatively low risks for the general population. Combustion by-products are often noted as a class of pollutants and arise from virtually all sources of combustiongas ovens, space heaters, woodstoves.
Tobacco smoke is also a source of combustion by-products.
VOCs, carbon monoxide, nitrogen dioxide, sulfur dioxide, PAHs, and particulates are included in this category. Exposures are virtually impossible to quantify owing to the limitless combinations of sources and activities in unique indoor environments. Instead, projects tend to rely on identifying housing and heating trends to characterize the problemnorthern projects cited long winters and energy efficient housing as causes for elevated concern. The overall impacts of indoor air pollution on quality of life were ranked low by a majority of projects. Because resulting health problems are not always attributed to indoor air problems, it is impossible to estimate the true magnitude of economic impact.