Browsing by Author "Amit Garg"

Now showing 1 - 2 of 2

Ambient air pollution and daily mortality in ten cities of India: a causal modelling study
(Elsevier B.V., 2024) Jeroen de Bont; Bhargav Krishna; Massimo Stafoggia; Tirthankar Banerjee; Hem Dholakia; Amit Garg; Vijendra Ingole; Suganthi Jaganathan; Itai Kloog; Kevin Lane; Rajesh Kumar Mall; Siddhartha Mandal; Amruta Nori-Sarma; Dorairaj Prabhakaran; Ajit Rajiva; Abhiyant Suresh Tiwari; Yaguang Wei; Gregory A Wellenius; Joel Schwartz; Poornima Prabhakaran; Petter Ljungman
Background: The evidence for acute effects of air pollution on mortality in India is scarce, despite the extreme concentrations of air pollution observed. This is the first multi-city study in India that examines the association between short-term exposure to PM2·5 and daily mortality using causal methods that highlight the importance of locally generated air pollution. Methods: We applied a time-series analysis to ten cities in India between 2008 and 2019. We assessed city-wide daily PM2·5 concentrations using a novel hybrid nationwide spatiotemporal model and estimated city-specific effects of PM2·5 using a generalised additive Poisson regression model. City-specific results were then meta-analysed. We applied an instrumental variable causal approach (including planetary boundary layer height, wind speed, and atmospheric pressure) to evaluate the causal effect of locally generated air pollution on mortality. We obtained an integrated exposure–response curve through a multivariate meta-regression of the city-specific exposure–response curve and calculated the fraction of deaths attributable to air pollution concentrations exceeding the current WHO 24 h ambient PM2·5 guideline of 15 μg/m3. To explore the shape of the exposure–response curve at lower exposures, we further limited the analyses to days with concentrations lower than the current Indian standard (60 μg/m3). Findings: We observed that a 10 μg/m3 increase in 2-day moving average of PM2·5 was associated with 1·4% (95% CI 0·7–2·2) higher daily mortality. In our causal instrumental variable analyses representing the effect of locally generated air pollution, we observed a stronger association with daily mortality (3·6% [2·1–5·0]) than our overall estimate. Our integrated exposure–response curve suggested steeper slopes at lower levels of exposure and an attenuation of the slope at high exposure levels. We observed two times higher risk of death per 10 μg/m3 increase when restricting our analyses to observations below the Indian air quality standard (2·7% [1·7–3·6]). Using the integrated exposure–response curve, we observed that 7·2% (4·2%–10·1%) of all daily deaths were attributed to PM2·5 concentrations higher than the WHO guidelines. Interpretation: Short-term PM2·5 exposure was associated with a high risk of death in India, even at concentrations well below the current Indian PM2·5 standard. These associations were stronger for locally generated air pollutants quantified through causal modelling methods than conventional time-series analysis, further supporting a plausible causal link. Funding: Swedish Research Council for Sustainable Development. © 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license
Synergistic associations of ambient air pollution and heat on daily mortality in India
(Elsevier Ltd, 2025) Jeroen de Bont; Ajit Rajiva; Siddhartha Mandal; Massimo Stafoggia; Tirthankar Banerjee; Hem H. Dholakia; Amit Garg; Vijendra Ingole; Suganthi Jaganathan; Itai Kloog; Bhargav Krishna; Kevin James Lane; R. K. Mall; Jyothi S. Menon; Amruta Nori-Sarma; Dorairaj Prabhakaran; Abhiyant Suresh Tiwari; Yaguang Wei; Gregory A. Wellenius; Joel D. Schwartz; Poornima Prabhakaran; Petter L.S. Ljungman
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. © 2025 The Authors