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How does indoor air pollution differ from outdoor air pollution?

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Dense smog and orange haze blanket the skyline of Mexico City at sunset, with buildings in the Polanco neighborhood partially obscured by air pollution. — air pollution Pollution darkening the skies over Mexico City.

Indoor air pollution differs from outdoor air pollution primarily in its sources and concentration. Indoor pollutants can include combustion products from stoves and heaters, volatile organic compounds (VOCs) from household products, and biological contaminants like bacteria, viruses, and mold. These can accumulate due to reduced air exchange rates in buildings, often for energy conservation.1

Outdoor air pollution, on the other hand, typically stems from larger-scale sources like vehicle emissions, industrial processes, and power plants. Common outdoor pollutants include sulfur dioxide, nitrogen oxides, carbon monoxide, ozone, and particulate matter. While both indoor and outdoor air pollution pose health risks, the specific contaminants and their origins distinguish the two.234516