Air pollution comes in many forms.

There are two main types of air pollution: indoor and outdoor.


Indoor air pollution comes chiefly from the burning of wood, charcoal, animal dung and other so-called “solid fuels” which are used by billions around the world for cooking. When these fuels are set ablaze, they release microscopic specs of dust, soot and black carbon, which are collectively known as fine particulate matter.


Outdoor air pollution comes from an array of sources, including factories, motor vehicles – even forest fires and dust storms. Experts say the most concerning pollutants are:

• PM 10 and its smaller cousin PM 2.5, two types of fine particulate matter that often spring from the burning of fossil fuels;
• carbon monoxide, an odourless gas that commonly comes from the combustion of wood, kerosene and charcoal;
• ground-level ozone, a major component of smog that is created when sunlight comes into contact with certain gasses; and
• nitrogen dioxide  (NO₂) and sulfur dioxide (SO₂), two compounds often produced by fossil-fuel-burning factories and vehicles.