Short-term exposure to fine particulate pollution and elderly mortality in Chile

Exposure to fine particulate matter (PM2.5) is known to cause adverse health outcomes. Most of the evidence has been derived from developed countries, with lower pollution levels and different demographics and comorbidities from the rest of the world. Here we leverage new satellite-based measurements of PM2.5, combined with comprehensive public records in Chile, to study the effect of PM2.5 pollution on elderly mortality. We find that a 10 µg/m3 monthly increase in PM2.5 exposure is associated with a 1.7% increase (95% C.I.: 1.1–2.4%) in all-cause mortality for individuals aged 75+. Satellite-based measurements allow us to comprehensively investigate heterogeneous effects. We find remarkably similar effect sizes across baseline exposure, rural and urban areas, income, and over time, demonstrating consistency in the evidence on mortality effects of PM2.5 exposure. The most notable source of heterogeneity is geographical, with effects closer to 5% in the center-south and in the metropolitan area. Chile, a relatively new member of the Organization for Economic Co-operation and Development (OECD), has many environmental challenges due to its recent industrialization. Air pollution levels are far higher than in other wealthy nations, such as the United States or European countries’; many cities in Chile have annual PM2.5 concentrations above 20 µg/m3, exceeding the World Health Organization (WHO) guidelines of 5 µg/m3. Multiple studies have linked both chronic and acute PM2.5 exposure to adverse health outcomes including cardiovascular and respiratory diseases, as well as an increase in all-cause mortality. Older populations and infants are known to be particularly vulnerable to PM2.5 exposures. Historically, most research has been conducted in developed countries due to the availability of reliable public health statistics, comprehensive air pollution monitoring, and data on other variables that affect both air pollution and mortality. These countries typically have PM2.5 concentrations below 20 µg/m3. Developed countries also differ markedly in many dimensions, including population demographics, comorbidities, and healthcare infrastructure, from the rest of the world. The recent emergence of new data measurement techniques, in particular, remote sensing, opens the possibility of measuring air pollution exposure with complete spatial coverage and over a much longer time scale. Such measurements have been used to monitor air pollution globally and over time, and to study its impact on mortality outside the developed world. Recent work has studied the empirical relationship between satellite-based PM2.5 exposures and mortality in Africa, Indonesia, Brazil, and in cities in Latin America. For Chile, earlier studies on the short-term association between PM2.5 and health-related outcomes have used data from ground monitoring stations and focused on the capital, Santiago, and other cities, covering only a fraction of the country and population. More recent work that uses satellite-based estimates similarly only focuses on cities. In general, evidence from rural areas is scarce worldwide, and in particular in Latin America. Here we study the short-term effect of PM2.5 on elderly 75+ mortality in Chile, with complete geographical coverage of 327 communes from 2002 to 2019. We first validate satellite-based PM2.5 estimates using available ground-based measurements and then combine these with a recent national population census to estimate monthly population-weighted exposures to PM2.5 for each commune. We construct monthly commune-level mortality statistics using data from publicly available individual death certificates and official yearly population estimates.

Pablo Busch, Paulo Rocha, Kyung Jin Lee, Luis Abdón Cifuentes, Xiao Hui Tai