Tropical city air pollution led to 470,000 premature deaths in 2018

Some 470,000 people in cities near the equator died prematurely in 2018 because of air pollution, an analysis suggests. As the cities are expected to grow rapidly this century, the problem could become worse without new measures to reduce the pollution.

Karn Vohra at University College London and his colleagues analysed the rise in fine particulate pollution in 46 tropical cities, including Mumbai, Dhaka and Lagos, each of which is expected to have more than 10 million inhabitants by 2100. The researchers looked at satellite data collected between 2005 and 2018 by NASA and the European Space Agency.

They were able to decipher the long-term trends in fine particulate pollution in the air above each city by looking at how sunlight was scattered by the particles. From this, they found there was a 1.5-to-fourfold increase in this pollution for 33 of the cities during the study period.

Vohra says this rise is probably caused by increases in road traffic, refuse burning and the household use of charcoal.

The team then put the data into a health risk model that links a rise in exposure to fine particulate pollution to premature mortality. The results suggested that more than 30 per cent of known premature deaths in Asia are partly caused by this pollution, according to Vohra.

“These [particles] penetrate deep into our lungs and have been shown to impact just about every organ in our body,” he says.

The research indicates that Dhaka, the capital of Bangladesh, had the largest increase in premature deaths from air pollution during the study period. Between 2005 and 2018, about 24,000 more people in the city may have died prematurely because of air pollution.

The problem is worsening, both because more pollution is being generated and because the cities are growing. The research suggests that, across the tropics, there has been a 62 per cent increase in the number of premature deaths due to air pollution exposure between 2005 and 2018.

Vohra says even more people will die prematurely unless solutions are found. “Even if air quality is unchanged, urban population is increasing in all cities in the tropics, so this will inevitably increase urban exposure,” he says.

“I think this study gives a good overview of recent air pollution trends in rapidly growing cities across Africa, South and South-East Asia,” says Miranda Loh at the Institute of Occupational Medicine.

“Satellite data and models – as used in the article – are useful for this type of global analysis, especially if there is a lack of ground monitoring data. But if we want to better track population exposures, it is important to improve ground-level monitoring worldwide,” she says.

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