Air pollution occurs when gases, dust particles, fumes (or smoke) or odour are introduced into the atmosphere in a way that makes it harmful to humans, animals and plant. It is a major problem in Sierra Leone that causes illness. Major sources of air pollution in the cities especially Freetown, Makeni and Bo are vehicular exhaust emissions, industrial activities, road and building industries, all which produce enormous amounts of pollutants in their vicinity. These urban activities generate close to 80% of all carbon dioxide (CO2) as well as a significant amount of other greenhouse gases (GHG).

In Sierra Leone air pollution is perhaps not as wide varied as in the other countries. Most of the air pollution comes mainly from domestic sources and dust generated from the ground mostly in the dry season both in urban and rural areas. The domestic sources include basically smoke from chimney of kitchens, farm bush burning (bush fire) which could be menace especially in the surrounding rural villages in the Western area and the country’s interior and carbon monoxide and carbon dioxide from automobile exhaust pipes.

Mining also has a great effect on the quality of the air in country.  Since these mines need to blast through rock to get to an ore, dust is produced in the process.  Air pollution in the form of this dust generated by mining activities, is a serious cause of illnesses, generally in the form of respiratory disease in people and asphyxia of plants and trees. Although workers in the mining companies in Sierra Leone report respiratory problems, many of these effects are felt in areas surrounding open-pit mines.  Wind carries debris far from the source, creating a more widespread problem.

Outdoor air pollution is a mix of chemicals, particulate matter, and biological materials that react with each other to form tiny hazardous particles. It contributes to breathing problems, chronic diseases, increased hospitalization, and premature mortality. The concentration of particulate matter (PM) is a key air quality indicator since it is the most common air pollutant that affects short term and long term health in the country.

Sierra Leone is rated as the 17th most vulnerable countries in terms of air pollution. The causes of air pollution are multiple. Because many households use charcoal or wood as source of fuel for cooking and other related activities, this has led the amount of carbon dioxide produced in the cities to be on the rise. The people that live in Freetown are exposed to indoor and outdoor air pollution that can cause many different health problems (WHO).