The relationship between all-cause mortality and air pollution: a systematic review focusing on vulnerable populations

Abstract Introduction. Ambient air pollution is known to cause premature deaths worldwide, but gaps remain in understanding its impact on life expectancy across different vulnerable populations. Our objective was to conduct a systematic review of the association of long-term exposure to PM2.5, ozone, and nitrogen dioxide (NO2) on all-cause mortality, with a focus on vulnerable populations. Methods. We searched PubMed, MEDLINE, and Web of Science from January 1, 2000 to October 19, 2023 for studies examining the impact of air pollution on life expectancy or mortality. Two reviewers independently screened 3,764 abstracts and assessed 192 full-text articles. Studies were included if they examined long-term exposure (≥ 1 year) to ambient PM2.5, ozone, or NO2, and reported all-cause mortality. Risk of bias was evaluated using the ROBINS-E tool. Effect estimates for all-cause mortality and subgroup analyses focusing on vulnerable populations (older adults, historically minoritized racial groups, those with comorbidities or low socioeconomic status) were extracted. Results. Thirty-nine studies published from 2000 to 2023 were included. Most studies originated from North America (n = 22) and Europe (n = 9). Study size ranged from 2,734 to 73.4 million participants. Across studies, long-term exposure to PM2.5, ozone, and NO2was consistently associated with increased all-cause mortality, with a trend toward stronger associations among vulnerable populations including individuals with pre-existing health conditions, lower socioeconomic status, and urban residence. The highest mortality burden from air pollution was observed on Black Americans and adults aged 65–74. Conclusion. Long-term exposure to air pollution increases all-cause mortality and appears to disproportionately affect vulnerable populations.