For centuries people have suffered polluted and stale air inside cramped dwellings and huts. A significant contributor to indoor air pollution in many parts of the world is the smoke and fumes from burning dung, bark and wood indoors on open fires or simple stoves used for cooking, and for heating in alpine regions where indoor air pollution is aggravated by limiting ventilation to conserve heat.
New problems of indoor air pollution are arising from synthetic materials and structural techniques, and from construction materials whose constituents are potentially toxic or irritant and hence likely to produce allergic responses. The causes of such indoor pollution are not precise. The term may also be extended to cover tobacco smoke and body odour. It may include the combined effects of office machines and carpeting. Recent reports suggest that there is both direct and circumstantial evidence that exposure of the public to indoor air pollutants are large enough and widespread enough to account for a substantial amount of sickness and premature death.
Improvements in epidemiological research in the 1990s have revealed that human health may be affected by exposure to much lower levels of some common air pollutants than previously believed. Although eliminating the pollutants may not be feasible in the near future, air quality management should attempt to minimize the risk. This is a major conceptual development that became apparent in the mid-1990s.
The need for energy conservation has influenced the rate of air change in a building; better draught control can have the result that higher levels of pollutants now occur. In the USA it has been estimated that passive smoking aggravates indoor pollution to the extent of tens of billions of dollars in medical costs and absenteeism. The risks of of indoor pollution from tobacco smoke may be twice as great as the danger from radon gas and more than 100 times as great as from cancer-causing outdoor pollutants.