Impact of Ambient Ultrafine Particles on Cause-Specific Mortality in Three German Cities

Schwarz M, Schneider A, Cyrys J, Bastian S, Breitner S, Peters A. Am J Respir Crit Care Med. 2023 May 15;207(10):1334-1344. [CrossRef] [PubMed]

Rationale: Exposure to ambient air pollution has been associated with adverse effects on morbidity and mortality. Ambient ultrafine particles (UFPs) result from combustion of combustion of gas, coal or hydrocarbons, biomass burning (i.e. agricultural burning, forest fires and waste disposal), vehicular traffic and industrial emissions, tire wear and tear from car brakes, air traffic, seaport, maritime transportation, restoration and concrete processing, domestic wood stoves, outdoor burning, kitchen, and cigarette smoke. However, the evidence of the impact of UHFs on morbidity and mortality based on epidemiological studies remains scarce and inconsistent. Objectives: The authors examined associations between short-term exposures to UFPs and total particle number concentrations (PNCs; 10–800 nm) and cause-specific mortality in three German cities: Dresden, Leipzig, and Augsburg. Methods: We obtained daily counts of natural, cardiovascular, and respiratory mortality between 2010 and 2017. UFPs and PNCs were measured at six sites, and measurements of fine particulate matter (PM2.5; ⩽2.5 μm in aerodynamic diameter) and nitrogen dioxide were collected from routine monitoring. We applied station-specific confounder-adjusted Poisson regression models. We investigated air pollutant effects at aggregated lags (0–1, 2–4, 5–7, and 0–7 d after UFP exposure) and used a novel multilevel meta-analytical method to pool the results. Additionally, we assessed interdependencies between pollutants using two-pollutant models. Measurements and Main Results: For respiratory mortality, we found a delayed increase in relative risk of 4.46% (95% confidence interval, 1.52 to 7.48%) per 3,223-particles/cm3 increment 5–7 days after UFP exposure. Effects for PNCs showed smaller but comparable estimates consistent with the observation that the smallest UFP fractions showed the largest effects. No clear associations were found for cardiovascular or natural mortality. UFP effects were independent of PM2.5 in two-pollutant models. Conclusions: The authors found delayed effects for respiratory mortality within 1 week after exposure to UFPs and PNCs but no associations for natural or cardiovascular mortality.