Background Ambient air pollution is a major environmental cause of morbidity and mortality worldwide. Cities are generally hotspots for air pollution and disease. However, the exact extent of the health effects of air pollution at the city level is still largely unknown. We aimed to estimate the proportion of annual preventable deaths due to air pollution in almost 1000 cities in Europe.Methods We did a quantitative health impact assessment for the year 2015 to estimate the effect of air pollution exposure (PM 2•5 and NO 2 ) on natural-cause mortality for adult residents (aged ≥20 years) in 969 cities and 47 greater cities in Europe. We retrieved the cities and greater cities from the Urban Audit 2018 dataset and did the analysis at a 250 m grid cell level for 2015 data based on the global human settlement layer residential population. We estimated the annual premature mortality burden preventable if the WHO recommended values (ie, 10 µg/m³ for PM 2•5 and 40 µg/m³ for NO 2 ) were achieved and if air pollution concentrations were reduced to the lowest values measured in 2015 in European cities (ie, 3•7 µg/m³ for PM 2•5 and 3•5 µg/m³ for NO 2 ). We clustered and ranked the cities on the basis of population and age-standardised mortality burden associated with air pollution exposure. In addition, we did several uncertainty and sensitivity analyses to test the robustness of our estimates. FindingsCompliance with WHO air pollution guidelines could prevent 51 213 (95% CI 34 036-68 682) deaths per year for PM 2•5 exposure and 900 (0-2476) deaths per year for NO 2 exposure. The reduction of air pollution to the lowest measured concentrations could prevent 124 729 (83 332-166 535) deaths per year for PM 2•5 exposure and 79 435 (0-215 165) deaths per year for NO 2 exposure. A great variability in the preventable mortality burden was observed by city, ranging from 0 to 202 deaths per 100 000 population for PM 2•5 and from 0 to 73 deaths for NO 2 per 100 000 population when the lowest measured concentrations were considered. The highest PM 2•5 mortality burden was estimated for cities in the Po Valley (northern Italy), Poland, and Czech Republic. The highest NO 2 mortality burden was estimated for large cities and capital cities in western and southern Europe. Sensitivity analyses showed that the results were particularly sensitive to the choice of the exposure response function, but less so to the choice of baseline mortality values and exposure assessment method.Interpretation A considerable proportion of premature deaths in European cities could be avoided annually by lowering air pollution concentrations, particularly below WHO guidelines. The mortality burden varied considerably between European cities, indicating where policy actions are more urgently needed to reduce air pollution and achieve sustainable, liveable, and healthy communities. Current guidelines should be revised and air pollution concentrations should be reduced further to achieve greater protection of health in cities.

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Background Natural outdoor environments including green spaces play an important role in preserving population health and wellbeing in cities, but the number of deaths that could be prevented by increasing green space in European cities is not known. We aimed to estimate the number of natural-cause deaths among adult residents that could be prevented in cities in 31 European countries, if the WHO recommendation for universal access to green space was achieved. MethodsIn this health impact assessment study we focused on adult residents (aged ≥20 years; n=169 134 322) in 978 cities and 49 greater cities, in 31 European countries. We used two green space proxies: normalised difference vegetation index (NDVI), and percentage of green area (%GA). The exposure was estimated at a fine grid-cell level (250 m × 250 m) and the preventable mortality burden for 2015 was estimated at the local city-level.Findings For 2015 we found that meeting the WHO recommendation of access to green space could prevent 42 968 (95% CI 32 296-64 177) deaths annually using the NDVI proxy (ie, 20% [95% CI 15-30] of deaths per 100 000 inhabitants-year), which represents 2•3% (95% CI 1•7-3•4) of the total natural-cause mortality and 245 (95% CI 184-366) years of life lost per 100 000 inhabitants-year. For the %GA proxy 17 947 (95%CI 0-35 747) deaths could be prevented annually. For %GA the number of attributable deaths were half of that of the NDVI and results were non-significant due to the exposure response function considered. The distribution of NDVI and %GA varied between cities and was not equally distributed within cities. Among European capitals, Athens, Brussels, Budapest, Copenhagen, and Riga showed some of the highest mortality burdens due to the lack of green space. The main source of uncertainty for our results was the choice of the agestructures of the population for the NDVI analysis, and exposure-response function for the %GA analysis.Interpretation A large number of premature deaths in European cities could be prevented by increasing exposure to green space, while contributing to sustainable, liveable and healthy cities.