Inhalation

INH0422

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Greater associations between risk of mortality and long-term exposures to relatively low concentrations of fine particulate matter (PM2.5) have been reported. Recognizing “more stringent air quality standards and guidelines will likely be considered,” The Health Effects Institute has funded three studies—in the United States, Europe and Canada—“to explore health effects from air pollution exposure at levels below government recommended standards.” BACK PAGE Inhalation April 2022 39 Health effects of long-term exposure to levels of air pollution below government-recommended standards Associations of mortality coincide with current EPA review of US national air quality standard "Although air pollution concen- trations have been declining over the past few decades in many high- er-income countries, several stud- ies published in the past decade have reported greater associations between risk of mortality and long- term exposures to relatively low concentrations [of fine particulate matter, 2.5 microns or smaller in diameter] PM 2.5 ," according to the Health Effects Institute (HEI). e United State Environmental Protection Agency (EPA) indicates that PM 2.5 has many sources. Some particles are "emitted directly from sources such as construction sites, unpaved roads, fields, smokestacks or fires." However, "most particles form in the atmosphere as a result of complex reactions of chemicals such as sulfur dioxide and nitrogen oxides, which are pollutants emit- ted from power plants, industrial facilities and vehicles." Recognizing that "more stringent air quality standards and guide- lines will likely be considered in the future," HEI has funded three studies—in the United States, Europe and Canada—"to explore health effects from air pollution exposure at levels below govern- ment recommended standards." e US study, "Assessing health effects of long-term exposure to low levels of ambient air pollution: Implementation of casual inference methods" was led by Francesca Dominici, PhD, Professor of Bio- statistics, Population Health and Data Science at Harvard Univer- sity's T.H. Chan School of Public Health and her colleagues. Results were published in January 2022. A report from the study in Europe was released in September 2021 and final results from the study in Canada are expected later in 2022. A focus on small cities and rural areas in the low-exposure subcohort e four-year US study used pub- lic data to evaluate "the risk of mortality associated with expo- sure to low ambient air pollution concentrations in a cohort of 68.5 million older Americans." All were recipients of Medicare, the United States government national health insurance program for Americans age 65 or older. According to HEI documents and e New York Times, the main anal- ysis determined the risk for the older US population as a whole. However, in the low- exposure sub- cohort, the researchers purposely excluded participants in large areas of the Eastern US and likely most people in most major cities. Instead, they focused on smaller towns and rural areas that were not well monitored by the EPA, either because they are sparsely populated or because pollution levels are not considered as high as in cities or along the congested East Coast. e researchers developed annual exposure models for PM 2.5 , ozone (O 3 ) and nitrogen dioxide (NO 2 ) at a spatial resolution of 1 km x 1 km for the years 2000 to 2016 to estimate exposure for all study participants. ey also conducted analyses of the exposure/health connection and presented results from three newly developed causal inference approaches and two tra- ditional regression approaches for estimating the risk of dying associ-

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