Review of long-term exposure to road traffic-related air pollution and mortality: Mechanism, exposure, and meta-analysis

Traffic-related air pollution (TRAP) is a significant risk factor influencing global public health, and an increasing number of studies have highlighted its impacts on diverse adverse health outcomes. In this study, we conducted a systematic review and meta-analysis of cohort and case-control studies identified in PubMed, Web of Science and Embase from database inception to Dec 1, 2025, to evaluate the long-term exposure of TRAP on all-cause and cause-specific mortality. Of the 13, 435 records screened, 64 studies were included in the systematic review. We found significant associations between long-term TRAP exposure and elevated risks of multiple mortality outcomes. The pooled risk ratios per 10 μg/m 3 increase in nitrogen dioxide were 1.04 (95% CI: 1.03–1.06), 1.05 (1.02–1.08), and 1.04 (1.02–1.07) for all-cause, cardiovascular, and respiratory mortality, respectively, and per 10 μg/m 3 increase in fine particulate matter were 1.09 (1.05–1.13), 1.07 (1.05–1.08), and 1.08 (0.94–1.24), respectively. However, no significant differences were observed between the health effects of TRAP exposure and those of ambient air pollution. Stratified meta-analysis revealed greater risks in studies employing dispersion models for exposure assessment than in those using land-use regression models. Moreover, a considerable proportion of epidemiological studies utilizing source apportionment methods reported higher health risks associated with TRAP. We propose that the adoption of various exposure assessment methods could introduce differences in the magnitude of the associations and that the health impacts of TRAP exposure may be underestimated. Future studies are needed to explore traffic-specific exposure-response functions to more accurately estimate TRAP-related health risks.