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Exploring Air Pollution and COVID-19 Linkages in South Asia  

Muthukumara Mani and Takahiro Yamada

South Asia is at the epicenter of the global air pollution problems and still evolving in COVID-19 cases and fatalities. There is growing evidence of increased rates of COVID-19 in areas with high levels of air pollution. Air pollution is found to cause cellular damage and inflammation throughout the body and has been linked to higher rates of diseases, including cancer, heart disease, stroke, diabetes, asthma, and other comorbidities. All these conditions also potentially increase the risk of death in COVID-19 patients. The causal link between the exposure to air pollution and COVID-19 is still under investigation around the world, underpinned by rigorous scientific research and peer-review processes. However, in terms of the approach after a careful review of the literature, the instrumental variable (IV) approach is a prospective candidate to establish causality in a reduced-form analysis to overcome endogeneity and measurement errors of air pollution level. An analysis, therefore, using sufficiently anonymized individual and household level information on COVID-19, household air pollution, and other individual and household socioeconomic endowments in the same primary sampling unit (PSU) of the individual and household survey would be necessary to establish the causality. The PSU data are usually available from demographic health surveys (DHS) with randomly displaced location information to maintain anonymity. Also, for the instrument of the exposure to ambient air pollution, the use of thermal inversions is suggested conditional on weather-related variables—for example, temperature, precipitation, wind velocity and direction, and humidity.


Epigenetics and the Exposome: Environmental Exposure in Disease Etiology  

Paolo Vineis and Federica Russo

While genomics has been founded on accurate tools that lead to a limited amount of classification error, exposure assessment in epidemiology is often affected by large error. The “environment” is in fact a complex construct that encompasses chemical exposures (e.g., to carcinogens); biological agents (viruses, or the “microbiome”); and social relationships. The “exposome” concept was then put forward to stress the relatively poor development of appropriate tools for exposure assessment when applied to the study of disease etiology. Three layers of the exposome have been proposed: “general external” (including social capital, stress and psychology); “specific external” (including chemicals, viruses, radiation, etc.); and “internal” (including for example metabolism and gut microflora). In addition, there are at least three properties of the exposome: (a) it is based on a refinement of tools to measure exposures (including internal measurements in the body); (b) it involves a broad definition of “exposure” or environment, including overarching concepts at a societal level; and (c) it involves a temporal component (i.e., exposure is analyzed in a life-course perspective). The conceptual and practical challenge is how the different layers (i.e., general, specific external, and internal) connect to each other in a causally meaningful sequence. The relevance of this question pertains to the translation of science into policy—for example, if experiences in early life impact on the adult risk of disease, and on the quality of aging, how is distant action to be incorporated in biological causal models and into policy interventions? A useful causal theory to address scientific and policy question about exposure is based on the concept of information transmission. Such a theory can explain how to connect the different layers of the exposome in a life-course temporal frame and helps identify the best level for intervention (molecular, individual, or population level). In this context epigenetics plays a key role, partly because it explains the long-distance persistence of epigenetic changes via the concept of “epigenetic memory.”


Environmental Degradation: Estimating the Health Effects of Ambient PM2.5 Air Pollution in Developing Countries  

Ernesto Sánchez-Triana, Bjorn Larsen, Santiago Enriquez, and Andreia Costa Santos

Air pollution of fine particulates (PM2.5) is a leading cause of mortality worldwide. It is estimated that ambient PM2.5 air pollution results in between 4.1 million and 8.9 million premature deaths annually. According to the World Bank, the health effects of ambient PM2.5 air pollution had a cost of $6.4 trillion in purchasing power parity (PPP) adjusted dollars in 2019, equivalent to 4.8% of global gross domestic product (PPP adjusted) that year. Estimating the health effects and cost of ambient PM2.5 air pollution involves three steps: (1) estimating population exposure to pollution; (2) estimating the health effects of such exposure; and (3) assigning a monetary value to the illnesses and premature deaths caused by ambient air pollution. Estimating population exposure to ambient PM2,5 has gone from predominantly using ground level monitoring data mainly in larger cities to estimates of nationwide population weighted exposures based on satellite imagery and chemical transport models along with ground level monitoring data. The Global Burden of Disease 2010 (GBD 2010) provided for the first time national, regional and global estimates of exposures to ambient PM2.5. The GBD exposure estimates have also evolved substantially from 2010 to 2019, especially national estimates in South Asia, the Middle East and North Africa, Sub-Saharan Africa and Latin America and the Caribbean. Estimation of health effects of ambient PM2.5 has also undergone substantial developments during the last two decades. These developments involve: i) going from largely estimating health effects associated with variations in daily exposures to estimating health effects of annual exposure; ii) going from estimating all-cause mortality or mortality from broad disease categories (i.e., cardiopulmonary diseases) to estimating mortality from specific diseases; and iii) being able to estimate health effects over a wide range of exposure that reflect ambient and household air pollution exposure levels in low- and middle-income countries. As to monetary valuation of health effects of ambient air pollution, estimates in most low- and middle-income countries still rely on benefit transfer of values of statistical life (VSL) from high-income countries.


Household Air Pollution in Low and Middle Income Countries  

Caroline A. Ochieng, Cathryn Tonne, Sotiris Vardoulakis, and Jan Semenza

Household air pollution from use of solid fuels (biomass fuels and coal) is a major problem in low and middle income countries, where 90% of the population relies on these fuels as the primary source of domestic energy. Use of solid fuels has multiple impacts, on individuals and households, and on the local and global environment. For individuals, the impact on health can be considerable, as household air pollution from solid fuel use has been associated with acute lower respiratory infections, chronic obstructive pulmonary disease, lung cancer, and other illnesses. Household-level impacts include the work, time, and high opportunity costs involved in biomass fuel collection and processing. Harvesting and burning biomass fuels affects local environments by contributing to deforestation and outdoor air pollution. At a global level, inefficient burning of solid fuels contributes to climate change. Improved biomass cookstoves have for a long time been considered the most feasible immediate intervention in resource-poor settings. Their ability to reduce exposure to household air pollution to levels that meet health standards is however questionable. In addition, adoption of improved cookstoves has been low, and there is limited evidence on how the barriers to adoption and use can be overcome. However, the issue of household air pollution in low and middle income countries has gained considerable attention in recent years, with a range of international initiatives in place to address it. These initiatives could enable a transition from biomass to cleaner fuels, but such a transition also requires an enabling policy environment, especially at the national level, and new modes of financing technology delivery. More research is also needed to guide policy and interventions, especially on exposure-response relationships with various health outcomes and on how to overcome poverty and other barriers to wide-scale transition from biomass fuels to cleaner forms of energy.