Pollution and exposure levels
People’s exposure to indoor air pollution is determined by the concentrations of pollutants in the indoor environment (mainly determined by the type of fuel and stove used, and the kitchen location) and, most importantly, by the time that individuals spend 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 benzo[a]pyrene and benzene.
Small particles with a diameter of 10 microns (PM10) or less are able to penetrate deep into the lungs and appear to have the greatest health-damaging potential.
Studies from Asia, Africa and the Americas have shown that indoor air pollution levels in households reliant on biomass fuel or coal are extremely high, for example, typical 24 hour mean levels for PM10 in homes using biomass fuels are around 1000 µg/m3, compared to the current limit of 150 µg/m3 set by the United States Environmental Protection Agency. Thus typical concentrations of indoor air pollutants exceed generally accepted guideline limits many times.
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 indoor 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 smoke from early infancy.