Air pollution

A set of substances present in the air, apart from those habitually making up the atmosphere, in a concentration such that they negatively affect both people and other living beings. Air pollution can have a natural origin (volcanic eruptions, wildfires not caused by man...) or an artificial one (industrial activities, traffic...). In the latter case, it is also known as atmospheric pollution. Pollutants present in the air can be of very different natures: toxic gases, smoke, smog, volcanic ash, radioactive material... In urban areas, exposure to high levels of ozone, nitrogen dioxide, and particulate matter (PM) carries a high risk to human health, with increasing evidence of that impact.