Air pollution responsible for 180,000 excess deaths in tropical cities

New research from University College London reveals rapid degradation in air quality and increases in urban exposure to air pollutants hazardous to health in 46 future megacities in Africa, Asia and the Middle East.

The international team of scientists aimed to address data gaps in air quality for the emerging megacities using space-based observations from NASA and European Space Agency satellites for 2005 to 2018.

Across the cities, the researchers found significant annual increases in pollutants directly hazardous to health of up to 14% for nitrogen dioxide (NO2) and up to 8% for fine particulate matter (PM2.5).

They also found increases in precursors of PM2.5 of up to 12% for ammonia and up to 11% for reactive volatile organic compounds.

The researchers attributed this rapid degradation in air quality to emerging industries and residential sources like road traffic, waste burning, and widespread use of charcoal and fuelwood.

Lead author Dr Karn Vohra, UCL Department of Geography, said: ‘Open burning of biomass for land clearance and agricultural waste disposal has in the past overwhelmingly dominated air pollution in the tropics. 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 that a combination of population growth and rapid deterioration in air quality led to a 1.5 to 4-times increase in urban population exposure to air pollution over the study period in 40 of the 46 cities for NO2 and 33 of the 46 cities for PM2.5.

According to the study, 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 (totalling 24,000 people), and the Indian cities of Mumbai, Bangalore, Kolkata, Hyderabad, Chennai, Surat, Pune and Ahmedabad (totalling 100,000 people).

Study co-author Dr Eloise Marais, UCL Geography, said: ‘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.’

Photo by Shafiqul Islam