Indoor air pollution

Pollution sources and levels

People’s exposure to household air pollution is determined by the concentrations of pollutants in the household environment (mainly determined by the type of fuel and stove used, the kitchen location and the ventilation) and, most importantly, by the time that individual spends in polluted environments.

Indoor smoke contains a variety of health-damaging pollutants:

  • particles (complex mixtures of chemicals in solid form and droplets)
  • carbon monoxide
  • nitrous oxides
  • sulphur oxides (mainly from coal)
  • formaldehyde
  • carcinogens (chemical substances known to increase the risk of cancer) such as benzene.

Small particles with a diameter of 2.5 microns (PM2.5) or less are able to penetrate deep into the lungs and appear to have the greatest effects on health.

photo of woman cooking
Copyright: Nigel Bruce

Studies from Asia, Africa and the Americas have shown that air pollution levels in households reliant on biomass fuels or coal are extremely high, exceeding several times the recommended WHO guideline of an annual mean of 10 µg/m3 for PM2.5

In most societies, it is women who cook and spend time near the fire, and in developing countries they are typically exposed to these very high levels of household air pollution for between 3 and 7 hours per day over many years. Young children are often carried on their mother’s back during cooking. Consequently, they spend many hours breathing in harmful smoke from early infancy.