Global cities with the best and worst air quality

Kailua-Kona in Hawaii is one of the towns and cities with the best air quality in the world. Photo: AFP

The British company HouseFresh has drawn up a map of the 50 most polluted cities in the world. While the worst offenders are all located in Asia, it is a city in Australia that wins the prize for the "cleanest air".

Natural disasters such as forest fires or sandstorms play a major role in the air quality of the cities featured in this study.

The ranking was based on a 2020 air quality report by Swiss air quality expert IQAir. Countries and cities were evaluated according to their fine particle concentration (PM2.5).

Of the 50 most polluted cities in the world, 49 are in Bangladesh, Pakistan, China and India.

The most polluted city of 2020 is Hotan (Xinjiang, China), with a PM2.5 concentration of 110.2µg/m3. This high level of fine particles is, according to the authors of the study, directly related to local sandstorms.

The city of Hotan is indeed located at the southwestern edge of the Taklamakan Desert, the largest shifting sand desert in the world.

The second most polluted city in the ranking is in India. In Ghaziabad, in the state of Uttar Pradesh, the PM2.5 concentration is 106.6µg/m3.

"Colloquially known as the gateway to its home state, massive traffic volumes were likely the cause of the high levels of air pollution," explain the authors of the study.

Finally, Manikganj (Bangladesh) takes third place, with a PM2.5 of 80.2µg/m3.

"As one of the fastest developing countries around the world, with its industrial sector growing at a rate of 13% per year, vehicles and industrial emissions are the major contributors to air pollution in this country of 165 million people," the report notes.

Pollution linked to natural disasters

As for the cities with the best air quality, the Japanese city of Obihiro leads the way in Asia with a PM2.5 of 5.6µg/m3. But Judbury (Tasmania, Australia) is the winner, with a PM2.5 level of 2.4µg/m3.

Next are the cities of Kailua-Kona (Hawaii, the United States) and Muonio (Finland) with fine particle concentrations of 2.6µg/m3 and 2.8µg/m3 respectively.

According to the study authors, the relative purity of the air in these metropolises is mainly related to their low population densities. Judbury, in a rural region of Tasmania, has a population of just 392, while Muonio has a population of 2,308. The population of Kailua-Kona is estimated at 11,975, the study says.

The map also highlights the impact of natural disasters on elevated fine particle levels in towns and cities. Like the sandstorms near Hotan, China, the metropolitan area of Susanville in California, for example, is experiencing major forest fires, making it the most polluted city in America with a PM2.5 of 26.2µg/m3. — AFP Relaxnews

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