On 31 December 2019, a cluster of unexplained pneumonia cases in Wuhan, Hubei, China was reported to the World Health Organization (WHO) ( WHO, 2020 a Wu et al., 2020). The lockdown period demonstrated that the expected future reductions in NO 2 in European urban areas are likely to lead to widespread increases in urban O 3 pollution unless additional mitigation measures are introduced. Despite NO 2 concentrations decreasing by approximately a third, total oxidant ( O x) changed little, suggesting that the reductions in NO 2 were substituted by increases in O 3. To put the 2020 changes into context, average NO 2 trends since 2010 were calculated, and the changes experienced across European urban areas in 2020 was equivalent to 7.6 years of average NO 2 reduction (or concentrations which might be anticipated in 2028). Across Europe, we estimate that NO 2 concentrations were 34 % and 32 % lower than expected for respective traffic and urban background locations, whereas O 3 was 30 % and 21 % higher (in the same respective environments) at the point of maximum restriction on mobility. Counterfactual, business-as-usual air quality time series are created using machine-learning models to account for natural weather variability. To investigate these changes, we analyse data from 246 ambient air pollution monitoring sites in 102 urban areas and 34 countries in Europe between February and July 2020. The aggressive curtailing of the European economy had widespread impacts on the atmospheric composition, particularly for nitrogen dioxide ( NO 2) and ozone ( O 3). I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.In March 2020, non-pharmaceutical intervention measures in the form of lockdowns were applied across Europe to urgently reduce the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus which causes the COVID-19 disease. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as. Author DeclarationsĪll relevant ethical guidelines have been followed any necessary IRB and/or ethics committee approvals have been obtained and details of the IRB/oversight body are included in the manuscript.Īll necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. The authors have declared no competing interest. We also show that neighboring countries applying less restrictive social distancing measures (as opposed to police-enforced home containment) experience a very similar time evolution of the epidemic. Extrapolating pre-lockdown growth rate trends, we provide estimates of the death toll in the absence of any lockdown policies, and show that these strategies might not have saved any life in western Europe. Comparing the trajectory of the epidemic before and after the lockdown, we find no evidence of any discontinuity in the growth rate, doubling time, and reproduction number trends. This phenomenological study assesses the impacts of full lockdown strategies applied in Italy, France, Spain and United Kingdom, on the slowdown of the 2020 COVID-19 outbreak.
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