Alongside ozone pollution, the main contributor to poor health from air pollution is particulate matter. In particular, very small particles of matter - termed ‘PM2.5‘, which are particles with a size (diameter) of less than 2.5 micrometres (µm). Smaller particles tend to have more adverse health effects because they can enter airways and affect the respiratory system.
How does exposure to PM2.5 vary across the world? In the chart you can see the distribution of the population-weighted mean exposure to PM2.5 each year based on various countries and how it changes throughout a 30 year period.
Pollution exposure is high in many low-to-middle income countries across Africa and Asia. In particular, concentrations are very high across North Africa, partly owed to drier conditions with more sand and dust sources. There, exposure can reach as high as 200µg per cubic meter. Compare this with Sweden where exposure levels are 5µg/m3 – 40 times lower.