Short-term effects of ultrafine particles on mortality

International audienceParticulate matter (PM) was estimated to cause 4.2 million deaths worldwide in 2019; however, evidence on which components are responsible for its effects on mortality remains inconsistent. Ultrafine particles (UFP, 10nm) and N25 (>25 nm) are associated with significant increases in relative risk (RR) of natural and cardiovascular disease mortality, at lags 0 to 3. For example, an interquartile range increase in UFP (IQR: 3804 particles/cm3) was associated with a 0.8% [95% confidence interval: 0.2%, 1.5%] increase in natural mortality and 1% (95% confidence interval: 0.2%, 1.8%) in cardiovascular mortality. A significant risk of cardiovascular mortality was also observed 4-6 days after exposure to most particle size modes. We did not find significant associations between particle modes and respiratory mortality.The Nucleation, Aitken, UFP and Ntotal (>10 nm) modes showed similar results, indicating that both UFP and Ntotal (>10 nm) could potentially be used as indicators for the health effects of the smallest aerosol size fractions, dominant in number. The health effects of the UFP mode remained statistically significant for natural mortality after adjusting for PM2.5. Similarly, the effects of the UFP mode remained significant for natural and cardiovascular mortality after individually adjusting for PM10 and NO2.Our preliminary results suggest that the smallest aerosol particle size fractions (e.g., UFP) may independently impact health