Exposure to air pollution has been linked to 100,000 excess premature deaths in the Indian cities of Mumbai, Bangalore, Kolkata, Hyderabad, Chennai, Surat, Pune and Ahmedabad between 2005 and 2018, according to a study.
The international team of scientists aimed to address data gaps in air quality in 46 cities in Africa, Asia and the Middle East using space-based observations from instruments onboard NASA and European Space Agency (ESA) satellites from 2005 to 2018.
The study, published last week in the journal Science Advances, shows rapid degradation in air quality and increases in urban exposure to air pollutants that are hazardous to health.
The researchers found significant annual increases in pollutants directly hazardous to the health of up to 14 per cent for nitrogen dioxide (NO2) and up to 8 per cent for fine particles (PM2.5).
They also found an increase in the level of up to 12 per cent for ammonia and up to 11 per cent for reactive volatile organic compounds.
The team, including researchers from the Harvard University in the US, 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.
"Open burning of biomass for land clearance and agricultural waste disposal has in the past overwhelmingly dominated air pollution in the tropics," said the study’s lead author Karn Vohra from University College London (UCL) in the UK.
"Our analysis suggests we are 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," said Vohra, who completed the study as a PhD student at the University of Birmingham, UK.
The researchers also found 1.5 to four-fold increases in urban population exposure to air pollution in 40 of the 46 cities for NO2 and 33 of the 46 cities for PM2.5, caused by a combination of population growth and rapid deterioration in air quality.
The study found that the increase in the number of people dying prematurely from exposure to air pollution was highest in cities in South Asia.
Dhaka, Bangladesh, saw a total of 24,000 excess premature deaths, while the Indian cities of Mumbai, Bangalore, Kolkata, Hyderabad, Chennai, Surat, Pune and Ahmedabad had 100,000 excess deaths.
The researchers noted that India has an extensive network of monitors operated and maintained by local and national authorities as well as research institutions.
However, the use of these for informing policies is hindered by data quality issues for the national network and restricted access to data collected by research institutions and state governments, they said.
The number of deaths in tropical cities in Africa is currently lower due to recent improvements in healthcare across the continent resulting in a decline in overall premature mortality, the researchers said.
However, the worst effects of air pollution on health will likely occur in the coming decades, they 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," said study co-author Eloise Marais from UCL.
"We hope our results will incentivise preventative action in the tropics," Marais added.