Resumen de Climate change and health in India - impacts and co-benefits
Due to its large and growing population and economy, India is pivotal for climate change mitigation globally. However, like other low- and middle-income countries (LMICs), India is also facing many other pressing development challenges. Country-level studies are needed to assess both the scale of India´s vulnerability to climate change as well as the extent to which mitigation actions can be reconciled with its development objectives. Given the complexity of projecting the interplay of human and environmental systems, studies with strong interdisciplinary foundations are required.
This PhD thesis presents an interdisciplinary approach to investigating the health impacts of climate change and the health co-benefits of climate change mitigation in India. The thesis draws from methods in epidemiology and demography and integrates substantive area knowledge regarding ambient and household air pollution, climate change health impacts and mitigation policies, and broader development issues in the Indian context.
The first chapter of this thesis offers a thorough background of the literature of health impacts of climate change, ambient air pollution and household air pollution; the specific context of India in terms of climate change vulnerability, potential co-benefits of mitigation, and policy priorities; and a more methodological section comparing different health impact modelling approaches.
Paper 1 “Association between ambient temperature and heat waves with mortality in South Asia: Systematic review and meta-analysis” addresses the need for robust and setting-specific exposure response functions between ambient temperature and mortality for impact estimation. As daily temperature and mortality data series are still missing for many countries in South Asia due to underdeveloped monitoring systems, population-specific exposure response functions are not easily estimated. Where such exposure-response functions exist, they are often based on populations of small size and a limited number of years. These gaps either hinder the development of future temperature-related projections or add large uncertainty to projected estimates. This first paper in the thesis conducted a comprehensive systematic review of the literature and meta-analysis of studies meeting specific inclusion criteria to derive the best available exposure-response function for ambient temperature and all-cause mortality in the region. This meta-analysis addresses an important data gap and supports future health impact assessment studies in a “data scarce” region, which is a hotspot of climate change impacts and urgently needs such projections for future planning. The meta-analysis included the application of a novel meta-analytic approach for combining exposure-response functions without access to individual study data. Synthesis of the literature in the review also included identifying research gaps, policy priorities, and vulnerable population groups. The paper was published in a journal with exceptionally high standards for systematic reviews.
Paper 2 “Health impacts of fine particles under climate change mitigation, air quality control, and demographic change in India” investigated the air pollution related health co-benefits of climate change mitigation in India. This paper went beyond prior studies by reporting impacts for distinct population groups (age, sex, urban-rural residence) and at a lower geographical aggregation than estimated in previous studies. In addition, health co-benefit estimates were reported as gains in life expectancy, which is a more informative summary measure of population health than number of attributable deaths. By modelling both climate change mitigation policies and targeted air quality control, the paper supports the conclusion that targeted air pollution control will always be necessary to protect public health; climate change mitigation can further add to health gains due to reduced air pollution. The paper presented several methodological advances including the consistent linkage of a multi-dimentional demographic projection and an integrated assessment model, which allowed for the feedback effects of air pollution on population survival over time to be included. This is an important consideration in settings such as India due to the large impacts of air pollution on life expectancy, thus providing more realistic estimates of the interplay between exposure and population dynamics over time.
The third paper “The impact of air pollution on child stunting in India – synergies and trade-offs between climate change mitigation, ambient air quality control, and clean cooking access” investigated potential trade-offs between clean energy access and ambient air pollution reduction and their impacts on child linear growth. This paper makes an important contribution to the literature in several ways. First, it considers a health outcome other than mortality, which has so far dominated the health co-benefits literature, and focuses on impacts in children, which have been far less considered in co-benefits studies. It considers child stunting, for which the epidemiology linking ambient and household air pollution has only recently emerged. Second, it considers the simultaneous impacts on health of two exposures. Third, it uses static microsimulation, which allows for the integration of complex population-environment interactions, multiple exposures pathways and differential population vulnerabilities. This modelling approach was based on exposure-response functions estimated directly in the population, avoiding extrapolation of this function across populations.
The discussion chapter of the thesis gives a balanced assessment of the strengths and limitations of the thesis overall and highlights areas for future research.
