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Abstract:
Aims Actions to reduce greenhouse gas emissions will also reduce emissions of air pollutants that are harmful to the health of children. This work aimed to assess the magnitude of air pollution reductions that could be achieved in 16 cities through ambitious global climate change mitigation action and the resulting impact on the health of children and young people.
Methods We modelled current concentrations of fine particulate matter (PM2.5) and nitrogen dioxide (NO2) air pollution at 1x1 km resolution in 16 global cities (Bhubaneswar, Dar es Salaam, Dhaka, Freetown, Glasgow, Harare, Jaipur, Lahore, London, Los Angeles, Manila, Mexico City, Milan, Nairobi, Quito and Tamale) using a general circulation/atmospheric chemistry model. Air pollution levels under a ‘net zero’ scenario were estimated by removing all global combustion-related emissions from land transport, industries, domestic energy use and energy generation. We calculated the resulting impact on childhood asthma incidence (from reduced NO2) and adverse birth outcomes (low birthweight and preterm births from reduced PM2.5) in each city using a comparative risk assessment approach, parameterised with country-specific asthma incidence and birth outcome data for 2019 from the Global Burden of Disease (GBD) study and exposure-response functions from high-quality published meta-analyses.
Results If global air pollution levels were reduced by actions to achieve net zero, we estimate that more than 20,000 cases of childhood asthma, 22,000 low birthweight births and 43,000 premature births could be averted annually across the 16 cities in total. This represents almost a quarter of the current annual asthma incidence in these cities and a reduction of about 10% for adverse birth outcomes. Figure 1 shows the results for each city (per 100,000 children for asthma and per 100,00 births for adverse birth outcomes). At city-level, Los Angeles, Mexico City, and Manila would see the greatest reduction in childhood asthma annually, with 7,200, 5,700 and 4,000 new cases averted respectively. Dhaka, Manila and Lahore would see the greatest reduction in premature births annually, with 23,800, 7,000 and 4,600 cases prevented respectively. The same cities would see the largest benefits with regard to low birthweight births, with 13,500, 2,500 and 3,100 cases averted. There are however large variations in the modelled impacts between cities and our estimates are less certain in some cities than others. In part, the large differences are likely to reflect greater uncertainty in the modelled air pollution reductions in some regions and significant limitations of the available health data in certain locations (in particular South Asia and Africa).
Conclusion Through analysis of 16 cities, this work demonstrates that reaching ‘net zero’ greenhouse gas emissions globally would lead to considerable reduction in air pollution with the benefit of substantial decreases in childhood asthma incidence and adverse birth outcomes. The results represent the effects of global action, rather than specific actions in individual cities, demonstrating the benefits of collective action for tackling climate change and reducing air pollution. Nonetheless, analyses of this type are constrained by a number of limitations, in particular poor health data in some areas.
