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Air pollution in tropical cities linked to 180,000 excess deaths

In a new study led by University College London, scientists report that air pollution has led to an increase of premature deaths in tropical cities across the world. Using observations from NASA and European Space Agency (ESA) satellites, the researchers assessed air quality for 46* future megacities in Africa, Asia and the Middle East.

The results revealed a decline in air quality and increase in urban air pollution hazardous to human health. Across all cities, a significant annual increase was identified of up to 14 percent for nitrogen dioxide (NO2) and up to eight percent for fine particles (PM2.5). 

An increase in precursors of fine particles were also found up to 12 percent for ammonia and up to 11 percent for reactive volatile organic compounds. This has been linked to emerging industries and residential sources like road traffic, waste burning, and widespread use of charcoal and fuelwood.

“Open burning of biomass for land clearance and agricultural waste disposal has in the past overwhelmingly dominated air pollution in the tropics,” said study lead author Dr. Karn Vohra. “Our analysis suggests we’re entering a new era of air pollution in these cities, with some experiencing rates of degradation in a year that other cities experience in a decade.”

The scientists also found staggering increases in urban population exposure to air pollution over the study period. Overall, 40 of the 46 cities had significant increases of nitrous oxide, while 33 cities showed an increase in fine particles. This is caused by population growth and rapid deterioration in air quality.

The increase in the number of people dying prematurely from exposure to air pollution was highest in cities in South Asia, in particular Dhaka, Bangladesh, with 24,000 deaths. As well as the Indian cities of Mumbai, Bangalore, Kolkata, Hyderabad, Chennai, Surat, Pune and Ahmedabad – accounting for a total of 100,000 deaths.

While the number of deaths in Africa’s tropical cities are lower due to recent improvements in healthcare, researchers believe the worst health effects of air pollution can be expected in the coming decades.

“We continue to shift air pollution from one region to the next, rather than learning from errors of the past and ensuring rapid industrialisation and economic development don’t harm public health. We hope our results will incentivise preventative action in the tropics,” said study co-author Dr Eloise Marais.

*Cities analyzed in the study:

  • Africa – Abidjan, Abuja, Addis Ababa, Antananarivo, Bamako, Blantyre, Conakry, Dakar, Dar es Salaam, Ibadan, Kaduna, Kampala, Kano, Khartoum, Kigali, Kinshasa, Lagos, Lilongwe, Luanda, Lubumbashi, Lusaka, Mombasa, N’Djamena, Nairobi, Niamey, Ouagadougou.
  • South Asia – Ahmedabad, Bangalore, Chennai, Chittagong, Dhaka, Hyderabad, Karachi, Kolkata, Mumbai, Pune, Surat.
  • Southeast Asia – Bangkok, Hanoi, Ho Chi Minh City, Jakarta, Manila, Phnom Penh, Yangon.
  • Middle East – Riyadh, Sana’a.

The study is published in the journal Science Advances.

By Katherine Bucko, Staff Writer

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