Health effects due to indoor air pollution

The indoor micro-environment has its own pollutants and pollution levels indoors may be higher than those outdoors. This is particularly so when there are combustion processes associated with cooking heating or smoking coupled with poor ventilation. About half the world's population have to rely for cooking; and associated space heating on simple household stoves using unprocessed solid fuels that have high emission factors, with the consequence that they are exposed to high levels of health-damaging air pollutants. Cooking can produce very high concentrations of particles and biomass fuels emit hundreds of chemicals during small-scale combustion, such as in household cooking or heating stoves. Tobacco smoke may add to other biomass smoke and all these together cause considerable human ill health world-wide. Most indoor air pollutants directly affect the respiratory and cardiovascular systems and the severity of the effect varies according to both the intensity and the duration of exposure, and also the health status of the population exposed. The importance of this is that some members of the population may be at greater risk than others. A number of the chemicals found in the in-door environment are classed as carcinogens although at the levels found the probability that they will cause cancer is extremely low. This is not to lessen the problem. In a 1987 study, the U.S. Environmental Protection Agency ranked indoor air pollution fourth in cancer risk among the 13 top environmental problems analysed.