Indoor air pollution is often two to five times as bad as outdoor pollution, and in some cases can even be more than 100 times worse than outdoor air. Common sources of indoor air pollution include the burning of heat sources, such as kerosene, coal, wood, oil and gas, as well as the smoking of tobacco and the use of household cleaning products. The effects of indoor air pollution are estimated to be responsible for 2.7% of disease worldwide, according to the World Health Organization. Children younger than 5 years old tend to be the most affected because they inhale more air in comparison with their body weight, and they tend to spend the most time in vulnerable areas, such as kitchens and schools.
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