More than eight in ten cities around the world are failing to deliver satisfactory air quality, a new report has found.

(above image: By 螺钉 – Own work, CC BY-SA 3.0)

Multinational air quality solutions provider IQAir has released the 2024 edition of its annual World Air Quality Report.

The report is based on data from more than 40,000 air quality monitoring stations across 8,954 locations in 138 countries, territories and regions. This was analysed by IQAir’s air quality scientists.

All up, the report found that only 17 percent of global cities meet the recommendations in the World Health Organization (WHO) guideline for concentrations of fine particulate matter (PM 2.5) in the atmosphere.

In terms of countries overall, PM2.5 concentrations exceeded the WHO guideline in 126 of 138 countries and regions.

In fact, just seven of the countries analysed met the guideline. These included Australia, Bahamas, Barbados, Estonia, Grenada, Iceland and New Zealand.

Also known as particle pollution (PM), particulate matters is a complex mixture of solid and liquid particles which are suspended in the air as either solids or liquids.

It is not a single pollutant but rather a mix of chemical species. Examples include nitrates, sulphates, organic chemicals, metals, soil or dust particles and allergens.

Particulate matter can be emitted directly from sources such as construction sites, wildfires and wood burning. Alternatively, it can be formed indirectly in the atmosphere through chemical reactions.

Of particular concern are very small particles known as fine particulate matter (PM 2.5). This refers to particles which are 2.5 micrometres in length or less.

These can penetrate deep into the lungs and can even enter the bloodstream. This can lead to respiratory and cardiovascular problems.

Under the World Health Organization Guidelines, concentrations of PM 2.5 should not exceed five milligrams per cubic meter (5 µg/m3) annually.

(image soure: 2024 Air Quality Report, IQ Air)

According to the report, Oceania ranks as the world’s cleanest region. All up, 57 percent of cities within this region met the WHO guideline. As mentioned above, both Australia and New Zealand met the guideline for the country overall.

By contrast, heavy pollution levels were found in Africa and Central & South Asia.

All up, the five most polluted countries were Chad, Bangladesh, Pakistan, Democratic Republic of Congo and India. In Chad, annual PM2.5 levels (91.8 µg/m3) exceeded the WHO recommendation by more than 18 times.

In terms of metropolitan areas, Byrnihat, India was the worst with an annual average PM2.5 concentration of 128.2 µg/m3 – more than 25 times the WHO recommendation.

All up, the region of Central & South Asia was home to the top seven most polluted cities in the world. India was home to six of the nine most polluted global cities.

Encouragingly, the report found that there has been progress in expanding air quality monitoring.

However, regions in which data monitoring is insufficient remain. Across Africa, for example, there is only one monitoring station which provides publicly accessible data in real-time for every 3.7 million people.

To bridge these gaps, the report says that low-cost air quality monitors used by citizen scientists, researchers, community advocates, and local organizations are critical.

Frank Hammes, Global CEO of IQAir, said that the importance of air quality data should not be underestimated.

“Air pollution remains a critical threat to both human health and environmental stability, yet vast populations remain unaware of their exposure levels,” Hammes said.

“Air quality data saves lives. It (air quality data) creates much needed awareness, informs policy decisions, guiding public health interventions, and empowers communities to take action to reduce air pollution and protect future generations.”

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