Chart of the week: Countries with the worst air pollution

WHO says 99 per cent of the world's population live in areas where air quality falls below recommended limits

Air pollution is a major health concern worldwide, yet most cities experience poor air conditions. According to the World Health Organisation, 99 per cent of the world's population live in areas that do not meet the recommended air quality levels. The latest World Air Quality Report by the Swiss company IQAir shows that 12 out of the 138 countries analysed (fewer than 10 per cent) have concentrations of PM2.5 fine particulates below the WHO guideline 5.0 µg/m³ (micrograms per cubic metre).

Most and least polluted regions

The World Air Quality Report ranks cities and countries according to their average PM2.5 concentration. These fine particles or chemicals in the atmosphere threaten the environment and the health of living organisms. New Delhi in India and N'Djamena in Chad have the highest PM2.5 concentrations, with 91.8 and 91.6 µg/m³, while the highest ranking countries are Chad and Bangladesh, with 91.8 and 78 µg/m³ PM2.5 concentrations, respectively.

Chad was also found to be the most polluted country in 2022 and 2024. Due to a lack of data in 2023, a direct comparison for that year is not available. Most of the nation's pollutants come from the Sahara, vehicle emissions, uncontrolled crop burning and pollutants from heavy industry.

Seven Caribbean countries are among the 12 with the lowest PM2.5 concentration. The Bahamas, and its capital, Nassau, have the lowest with 2.3 µg/m³.

The Middle East in 2024 “showed moderate improvements, with PM2.5 levels dropping in each country across the region”, the report states. Iraq and the UAE continue to be among the region's most polluted countries, with Iraq in 13th position and the Emirates 17th worldwide. However, the UAE experienced one of the most notable reductions in PM2.5 concentrations in the Middle East, a 22 per cent drop compared to 2023.

Risks from air pollution

PM2.5 refers to fine particulate matter that is less than or equal to 2.5 microns in diameter. To give an idea of the size, a single human hair is 50 to 180 microns. These particles are so small they can penetrate the lungs and, in some cases, enter the bloodstream.

Children are considered particularly vulnerable to air pollution because of their activity levels and behaviour, for example, the amount of time they spend outside. They are also susceptible because their breathing rates are higher than those of adults and they take in more air per kilogram of body weight.

What can governments and people do?

There is no one-size-fits-all solution but a series of actions can help reduce the problem. These include integrating WHO air quality guidelines into future standards, dedicating funding to renewable energy projects and increasing the number of government-operated air quality monitoring stations.

Individual actions include supporting air quality projects, reducing outdoor activities during times of high air pollution and improving indoor air quality with filtration and purification systems.