The World Health Organisation issued guidelines for the air's concentration of small particles in 2005. According to their research, any concentration which exceeds 20PM per cubic metre will have a direct effect on people's health and life expenctancy.

But more recent research conducted in 2015 revealed that the previous guidelines had underestimated the effect particulate matter has on people's health.

In response to this, the World Health Organisation said last year that the guidelines needed to be reviewed to reflect these findings. 

These are the latest figures available but there is reason to believe that some areas have got worse since the data was collected in 2012.

Some regions like Africa and parts of Asia have not collected or have collected very little information about the quality of their cities' air.

This is reflected here and does not mean these regions have respected the guidelines set out by the World Health Organisation but instead a lack of resources to test the air. 

Click on a city to see how polluted the air is and choose between layers to explore PM10 and PM2.5 levels in detail

 Air quality and

 health

How much does this cost?

What is particulate matter ?