ELAPSE (Effects of Low-Level Air Pollution: A Study in Europe) is a Europe-wide collaboration in a research project Mortality and morbidity effects of long-term exposure to low-level PM2.5, Black Carbon, NO₂ and O₃: an analysis of European cohorts. The Project is funded by Health Effects Institute under the RFA 14-3: Assessing Health Effects of Long-term Exposure to Low Levels of Ambient Air Pollution and runs from mid-2016 to mid-2019.

The Project addresses the issue of health effects at low air pollution levels by performing targeted analyses of all-cause and cause-specific mortality and morbidity endpoints within selected cohorts of the ESCAPE study with detailed individual data (~380,000 subjects) and in seven very large European administrative cohorts (> 35 million subjects). The analysis focuses on the pollutants PM2.5 (fine particles with an aerodynamic diameter of less than 2.5 μm), nitrogen dioxide (NO₂), and ozone (O₃), but also exploits the rich monitoring data of black carbon (BC) available from the ESCAPE study with high spatial resolution. Exposure assessment characterizes fine-scale intra-urban as well as between-urban air pollution contrasts using novel combinations of land use regression and dispersion models, routine monitoring data, and satellite observations.

Epidemiological cohort studies have consistently found associations between long-term exposure to outdoor air pollution and a range of morbidity and mortality endpoints. Recent evaluations by the World Health Organization and the Global Burden of Disease study have suggested that these associations may be non-linear, and persist at very low concentrations. However, uncertainty about the shape of the concentration-response function exists especially for the low and high ends of the concentration distribution, which is partly related to the scarcity of observations, particularly in the low range. In this study we focus on analyses contributing to knowledge about health effects of spatially resolved air pollution concentrations at low concentrations, defined as less than current EU, EPA, and WHO Limit Values or guidelines for PM2.5, NO₂, and O₃. Studies have focused especially on PM2.5, but increasingly associations with O₃ and NO₂ are reported, for NO₂ particularly in studies that accounted for its fine spatial scale variation. Very few studies have evaluated long-term morbidity and mortality effects of O₃.