Synergistic associations of ambient air pollution and heat on daily mortality in India

Background: Limited studies have evaluated the interaction between ambient air pollution and heat on mortality, especially in regions such as India, where extreme levels of both exposures occur frequently. Accordingly, we aimed to investigate the potential synergistic effects between ambient air pol...

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Main Authors: Jeroen de Bont, Ajit Rajiva, Siddhartha Mandal, Massimo Stafoggia, Tirthankar Banerjee, Hem Dholakia, Amit Garg, Vijendra Ingole, Suganthi Jaganathan, Itai Kloog, Bhargav Krishna, Kevin Lane, R.K. Mall, Jyothi Menon, Amruta Nori-Sarma, Dorairaj Prabhakaran, Abhiyant Suresh Tiwari, Yaguang Wei, Gregory A. Wellenius, Joel Schwartz, Poornima Prabhakaran, Petter Ljungman
Format: Article
Language:English
Published: Elsevier 2025-05-01
Series:Environment International
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Online Access:http://www.sciencedirect.com/science/article/pii/S0160412025001771
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author Jeroen de Bont
Ajit Rajiva
Siddhartha Mandal
Massimo Stafoggia
Tirthankar Banerjee
Hem Dholakia
Amit Garg
Vijendra Ingole
Suganthi Jaganathan
Itai Kloog
Bhargav Krishna
Kevin Lane
R.K. Mall
Jyothi Menon
Amruta Nori-Sarma
Dorairaj Prabhakaran
Abhiyant Suresh Tiwari
Yaguang Wei
Gregory A. Wellenius
Joel Schwartz
Poornima Prabhakaran
Petter Ljungman
author_facet Jeroen de Bont
Ajit Rajiva
Siddhartha Mandal
Massimo Stafoggia
Tirthankar Banerjee
Hem Dholakia
Amit Garg
Vijendra Ingole
Suganthi Jaganathan
Itai Kloog
Bhargav Krishna
Kevin Lane
R.K. Mall
Jyothi Menon
Amruta Nori-Sarma
Dorairaj Prabhakaran
Abhiyant Suresh Tiwari
Yaguang Wei
Gregory A. Wellenius
Joel Schwartz
Poornima Prabhakaran
Petter Ljungman
author_sort Jeroen de Bont
collection DOAJ
description Background: Limited studies have evaluated the interaction between ambient air pollution and heat on mortality, especially in regions such as India, where extreme levels of both exposures occur frequently. Accordingly, we aimed to investigate the potential synergistic effects between ambient air pollution and heat on daily mortality in India. Methods: We applied a time-series analysis for ten cities in India between 2008–2019. We assessed city-wide daily particulate matter ≤ 2.5 μm (PM2.5) and temperature levels using two nationwide spatiotemporal models. We estimated city-specific exposure-outcome associations through generalised additive Poisson regression models, and meta-analysed the associations. To evaluate the interaction between PM2.5 and air temperature (modelled at lag 0–1), a product term was incorporated between linear PM2.5 and non-linear air temperature. From this model, we estimated the effect of air pollution for increasing levels of temperature, and vice versa. Findings: Among ∼ 3.6 million deaths, we found that the association of PM2.5 on mortality was particularly stronger beyond the 75th percentile of temperature. When we compared the associations of PM2.5-mortality at the 75th and 99th temperature percentile, we observed an increase from 0.8 % (95 % CI: −0.3 %, 1.9 %) to 4.6 % (95 % CI: 2.9 %, 6.5 %) increase in mortality per 10 μg/m3 increments, respectively. In addition, we observed a 22.0 % (95 % CI: 13.5 %, 31.2 %) increase in daily mortality risk due to an increase in temperature from the 75th to the 99th city-specific percentiles. Percent change in mortality risk increased linearly from 8.3 % (95 % CI: 2.2 %, 14.9 %) when daily PM2.5 was 20 μg/m3 to 63.9 % (95 % CI: 38.7.%, 93.7 %) at 100 μg/m3. Interpretation: Our findings reveal a substantial synergistic interaction between ambient air pollution and temperature in India. This calls for efforts to tangibly reduce common sources of air pollution and climate change to immediately lower their combined effects on daily mortality and mitigate their long-term health consequences.
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spelling doaj-art-666f5ff2b79a4e448b50aaea7f0ce8942025-08-20T02:11:47ZengElsevierEnvironment International0160-41202025-05-0119910942610.1016/j.envint.2025.109426Synergistic associations of ambient air pollution and heat on daily mortality in IndiaJeroen de Bont0Ajit Rajiva1Siddhartha Mandal2Massimo Stafoggia3Tirthankar Banerjee4Hem Dholakia5Amit Garg6Vijendra Ingole7Suganthi Jaganathan8Itai Kloog9Bhargav Krishna10Kevin Lane11R.K. Mall12Jyothi Menon13Amruta Nori-Sarma14Dorairaj Prabhakaran15Abhiyant Suresh Tiwari16Yaguang Wei17Gregory A. Wellenius18Joel Schwartz19Poornima Prabhakaran20Petter Ljungman21Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; Corresponding author at: Institute for Environmental Medicine, Karolinska Institutet, Stockholm SE-171 76, Sweden.Centre for Chronic Disease Control, New Delhi, India; Ashoka University, Sonipat, India; Ben-Gurion University of the Negev, Beer-Sheva, IsraelCentre for Chronic Disease Control, New Delhi, India; Ashoka University, Sonipat, IndiaInstitute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; Department of Epidemiology, Lazio Region Health Service /ASL Roma 1, Rome, ItalyInstitute of Environment and Sustainable Development, Banaras Hindu University, Varanasi, IndiaSmart Prosperity Institute, University of Ottawa, CanadaPublic Systems Group, National Investment & Infrastructure Fund (NIIF) Chair in Environment, Social & Corporate Governance (ESG), Indian Institute of Management Ahmedabad, IndiaEnvironmental, Climate, and Urban Health Division, Vital Strategies, NY, USA; Office for National Statistics, Wales, Newport, UKInstitute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; Centre for Chronic Disease Control, New Delhi, India; Ashoka University, Sonipat, IndiaBen-Gurion University of the Negev, Beer-Sheva, Israel; Department of Environmental Medicine and Climate Science, Icahn School of Medicine at Mount Sinai, New York, NY, USASustainable Futures Collaborative, New Delhi, IndiaDepartment of Environmental Health, Boston University School of Public Health, Boston, MA, USADST-Mahamana Center of Excellence in Climate Change Research, Institute of Environment and Sustainable Development, Banaras Hindu University, Varanasi, IndiaCentre for Chronic Disease Control, New Delhi, India; Ashoka University, Sonipat, IndiaDepartment of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, USACentre for Chronic Disease Control, New Delhi, India; Public Health Foundation of India, New Delhi, IndiaNRDC India Private Limited, New Delhi, IndiaDepartment of Environmental Medicine and Climate Science, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, USADepartment of Environmental Health, Boston University School of Public Health, Boston, MA, USADepartment of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, USACentre for Chronic Disease Control, New Delhi, India; Ashoka University, Sonipat, IndiaInstitute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; Department of Cardiology, Danderyd Hospital, Stockholm, SwedenBackground: Limited studies have evaluated the interaction between ambient air pollution and heat on mortality, especially in regions such as India, where extreme levels of both exposures occur frequently. Accordingly, we aimed to investigate the potential synergistic effects between ambient air pollution and heat on daily mortality in India. Methods: We applied a time-series analysis for ten cities in India between 2008–2019. We assessed city-wide daily particulate matter ≤ 2.5 μm (PM2.5) and temperature levels using two nationwide spatiotemporal models. We estimated city-specific exposure-outcome associations through generalised additive Poisson regression models, and meta-analysed the associations. To evaluate the interaction between PM2.5 and air temperature (modelled at lag 0–1), a product term was incorporated between linear PM2.5 and non-linear air temperature. From this model, we estimated the effect of air pollution for increasing levels of temperature, and vice versa. Findings: Among ∼ 3.6 million deaths, we found that the association of PM2.5 on mortality was particularly stronger beyond the 75th percentile of temperature. When we compared the associations of PM2.5-mortality at the 75th and 99th temperature percentile, we observed an increase from 0.8 % (95 % CI: −0.3 %, 1.9 %) to 4.6 % (95 % CI: 2.9 %, 6.5 %) increase in mortality per 10 μg/m3 increments, respectively. In addition, we observed a 22.0 % (95 % CI: 13.5 %, 31.2 %) increase in daily mortality risk due to an increase in temperature from the 75th to the 99th city-specific percentiles. Percent change in mortality risk increased linearly from 8.3 % (95 % CI: 2.2 %, 14.9 %) when daily PM2.5 was 20 μg/m3 to 63.9 % (95 % CI: 38.7.%, 93.7 %) at 100 μg/m3. Interpretation: Our findings reveal a substantial synergistic interaction between ambient air pollution and temperature in India. This calls for efforts to tangibly reduce common sources of air pollution and climate change to immediately lower their combined effects on daily mortality and mitigate their long-term health consequences.http://www.sciencedirect.com/science/article/pii/S0160412025001771IndiaAmbient air pollutionHeatInteractionClimate change
spellingShingle Jeroen de Bont
Ajit Rajiva
Siddhartha Mandal
Massimo Stafoggia
Tirthankar Banerjee
Hem Dholakia
Amit Garg
Vijendra Ingole
Suganthi Jaganathan
Itai Kloog
Bhargav Krishna
Kevin Lane
R.K. Mall
Jyothi Menon
Amruta Nori-Sarma
Dorairaj Prabhakaran
Abhiyant Suresh Tiwari
Yaguang Wei
Gregory A. Wellenius
Joel Schwartz
Poornima Prabhakaran
Petter Ljungman
Synergistic associations of ambient air pollution and heat on daily mortality in India
Environment International
India
Ambient air pollution
Heat
Interaction
Climate change
title Synergistic associations of ambient air pollution and heat on daily mortality in India
title_full Synergistic associations of ambient air pollution and heat on daily mortality in India
title_fullStr Synergistic associations of ambient air pollution and heat on daily mortality in India
title_full_unstemmed Synergistic associations of ambient air pollution and heat on daily mortality in India
title_short Synergistic associations of ambient air pollution and heat on daily mortality in India
title_sort synergistic associations of ambient air pollution and heat on daily mortality in india
topic India
Ambient air pollution
Heat
Interaction
Climate change
url http://www.sciencedirect.com/science/article/pii/S0160412025001771
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