Short-term exposure to air pollution and acute health effects in a low-pollution region, Baden-Wurttemberg, Germany

Background: The acute effects of short-term air pollution exposure on human health in regions with low pollution concentrations is not widely explored. This study assesses the risk of mortality and morbidity linked to short-term exposure to NO2 and PM2.5 in Baden-Wurttemberg, Germany, a region that broadly complies with European air quality standards and global guidelines. Methods: We applied a two-stage time-stratified case-crossover design followed by meta-analyses to estimate the relative risks of mortality (all-cause), hospital admission and sick leave (all-cause and cause-specific). Health outcomes between 2013 and 2022 were collected from the regional public insurance records, and exposures were derived from ensemble air quality models. Effect modification by SARS‑CoV‑2 (COVID-19) years, age, sex and urbanisation were also evaluated. Results: Short-term exposure to PM2.5 and NO2 was associated with increased risks of several acute health outcomes. Associations were observed for all-cause and cardiovascular-related hospital admissions, as well as sick leave, even at concentrations near the current daily limits set by the European Union. Effect estimates were generally more pronounced for NO2 and concentrated at immediate lag days. Exposure–response relationships were non-linear across health outcomes, and little evidence of effect modification by demographic or urbanisation characteristics was observed. Conclusion: This study provides evidence of acute health risks from short-term exposure to PM2.5 and NO2, even at concentrations below the suggested daily permissible levels, emphasising the need to reassess existing air quality standards.