Few studies have examined how air pollution and heat affect mortality, particularly in regions like India, where extreme exposure levels are common.
To address this, researchers from the Institute of Environmental Medicine, Karolinska Institutet, analyzed daily mortality data from ten Indian cities between 2008 and 2019. They used spatiotemporal models to assess city-wide levels of delicate particulate matter (PM2.5) and temperature to uncover potential combined effects on daily mortality.
The study highlights a worrying trend: extreme heat and high air pollution significantly increase mortality risks in Indian cities, far more than either factor individually. By analyzing 3.6 million deaths, researchers found that PM2.5’s impact on mortality is much stronger on extremely hot days.
For instance, a 10 μg/m³ rise in PM2.5 increased daily deaths by 4.6% on extremely hot days compared to just 0.8% on normal warm days. Similarly, mortality risk rose by 8.3% as temperatures shifted from warm to extremely hot at a PM2.5 level of 20 μg/m³—but soared to 64% when PM2.5 reached 100 μg/m³. The findings underscore the severe combined health risks of heat and air pollution.
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The research utilized time-series analyses with generalized additive Poisson regression models to explore how air pollution and heat influence mortality together. By examining their combined effects, the study estimated the impact of air pollution at varying temperature levels and vice versa.
The interaction between air pollution and extreme heat is particularly critical in densely populated areas where these factors often overlap. To reduce health risks, urgent action is needed to lower emissions from major sources of air pollution and combat climate change.
The study highlights the critical need for integrated strategies to tackle air pollution and climate change in India, where rising global temperatures will likely worsen existing challenges.
Reducing air pollution levels will almost immediately affect mortality from both air pollution and heat, with added health co-benefits.
Researchers also emphasized the importance of proactive measures, suggesting the development of integrated surveillance and warning systems. These systems would address climate hazards and air pollution levels, providing timely interventions and enhancing public safety.
The study reinforces that addressing shared pollutants can yield rapid and meaningful improvements for health and the environment.
Journal Reference:
- Jeroen de Bont, Ajit Rajiva et al. Synergistic associations of ambient air pollution and heat on daily mortality in India. Environment International. DOI: 10.1016/j.envint.2025.109426
Source: Tech Explorist
