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Several studies have already explored individual and environmental risk factors for COVID-19 morality, however most study populations consisted of the overall population and mainly from China or the US. Our study focused on COVID-19 mortality in the elderly in seven European cities. Long-term exposure to air pollution was estimated through annual pollutant concentrations at the residential address averaged over the last two years of the study period between February and May 2020. We focused on the main outdoor air pollutants PM10, PM2.5, NO2 and O3. Short-term variations in air pollutants and weather parameters (e.g. temperature, UV, relative humidity) were also examined through a 20-day period before the confirmed PCR diagnostic of COVID-19. Individual risk factors such as smoking status, sex, body mass index (BMI), ischemic heart disease, diabetes, hypertension, chronic renal failure, history of cancer, COPD, and lung fibrosis, were taken into account. We found positive associations for diabetes and COVID-19 mortality (OR 2.2 CI 95% :1.1, 4.4). Using a multivariate logistic regression model adjusted for all patient characteristics and city, we fail to reject the null hypothesis of no association between COVID-19 mortality and long-term and short-term increase in PM2.5, PM10, NO2 and O3. Our study suffers from the fact that patient profiles strongly differ between high-polluted and less-polluted cities. Strong differences in COVID-19 mortalities were observed between cities, which could be due to differences in COVID-19 management and treatment, such as accessibility to reanimation and intensive units between cities. Overall, our study highlights the need to improve estimation of individual exposure to air pollution. Indeed, even with the high-efficiency modelisation systems used in our study, we were unable to estimate the effect of air pollution within each city, because variations in air pollution exposure were too small. Individual markers of air pollution exposure such as recently demonstrated with urinary black carbon or passive individual samplers, would be most suitable for future explorations. Concerning weather parameters, although previous studies concluded that increase in temperature and UV index could decrease COVID-19 morality, our data did not allow us to reject the null hypotheses.

Local environmental organizations and media have recently expressed concerns over air pollution induced by maritime traffic and its potential adverse health effects on the population of Mediterranean port cities. We explore this issue with unique high-frequency data from Marseille, France’s largest port for cruise ships, over the 2008- 2018 period. Using a new pair-matching algorithm designed for time series data, we create hypothetical randomized experiments and estimate the variation in air pollutant concentrations caused by a short-term increase in cruise vessel traffic. We carry out a randomization-based approach to compute 95% Fisherian intervals (FI) for constant treatment effects consistent with the matched data and the hypothetical intervention. At the hourly level, cruise vessels’ arrivals increase concentrations of nitrogen dioxide (NO2) by 4.7 μg/m³ (95% FI: [1.4, 8.0]), of sulfur dioxide (SO2) by 1.2 μg/m³ (95% FI: [-0.1, 2.5]), and of particulate matter (PM10) by 4.6 μg/m³ (95% FI: [0.9, 8.3]). At the daily level, cruise traffic increases concentrations of NO2 by 1.2 μg/m³ (95% FI: [-0.5, 3.0]) and of PM10 by 1.3 μg/m³ (95% FI: [-0.3, 3.0]). Our results suggest that well-designed hypothetical randomized experiments provide a principled approach to better understand the negative externalities of maritime traffic.

Because the elderly account for 80% of deaths from COVID-19 and they may be more vulnerable to air pollution, in this retrospective study we aimed to explore individual and environmental risk factors for COVID-19 mortality in the geriatric departments of seven European University hospitals, between T. Bourdrel, L. Zabrocki et al.