According to the WHO, air pollution is now "the greatest environmental risk to health" . As well as being a major health issue, air pollution also has both an economic cost – estimated by the World Bank at about 5,000 billion dollars a year – and an environmental cost. Let's focus on an issue that is central to the concerns of public authorities and citizens alike.
Air pollution: a multifaceted reality
The WHO defines air pollution as "contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere". We can distinguish between two categories of atmospheric pollutants:
- primary pollutants, arising directly from sources of pollution: nitrogen monoxide, sulphur dioxide, carbon monoxide, fine particles or dust in suspension (PM2.5 and PM10), heavy metals, volatile organic compounds, hydrocarbons etc.
- secondary pollutants arising from chemical reactions between gases: ozone, nitrogen dioxide etc.
As an adult breathes in 15,000 litres of air a day on average, the presence of these pollutants in the air can contribute to the development or worsening of cardiovascular diseases, chronic lung diseases, respiratory infections etc. Thus, according to the WHO, exposure to indoor and outdoor air pollution leads to about seven million premature deaths worldwide every year, making it the fourth biggest factor in premature death at a global level.
Air pollution also has an impact on ecosystems, contributing to phenomena such as acid rain and eutrophication.