Written evidence submitted by L.Miguel Martins, Programme Leader, Toxicology Unit, University of Cambridge (AQU0076)

What does the early evidence from the COVID-19 pandemic say about the impact of poor air quality on health, and health inequalities for disadvantaged communities and other at-risk groups, and possible policy responses?

Thank you for your request and for the opportunity to contribute to this topic. I have written this reply in consultation with my research team. In April, we first deposited our study 1 with the title “Links between air pollution and COVID-19 in England” in the preprint server medRxiv. This was reported widely in the media (link here) and is undergoing peer review. We found a relationship between air quality and numbers of COVID-19 cases and deaths across England.

We used city-level ambient monitoring network data for the year 2019 to map the concentration of several air pollutants against the cumulative number of COVID-19 cases and deaths reported up to and including April 10th, 2020 - thus including the peak period of daily COVID-19 laboratory-confirmed cases in the current outbreak, before lockdown measures were implemented to control the pandemic. In our primary analysis, we found that as region-level concentrations of traffic-related pollutants increased, so did numbers of COVID-related cases, independent of population density in the study areas. In addition, our data highlighted that the largest number of COVID-19 deaths reported by April 10th in England occurred in London and the Midlands, where the annual average concentration (μg/m3) of nitrogen oxides was highest in the year prior to the COVID-19 outbreak. In order to estimate the impact of individual air pollutant species on the cumulative number of COVID-19 deaths and cases in each local authority, we reported the levels of ozone, nitrogen oxide, nitrogen, sulphur dioxide, PM2.5 and PM10 as averages of the 10 values measured nearest the centre of each local authority in England.

We found an association between higher levels of nitrogen and sulphur dioxide with an increase in both COVID-19 cases and deaths, after adjusting for local authority-level differences in age, mean annual earnings and population density. Specifically, our models predicted that a 1 μg/m3 increase in sulphur dioxide concentration was associated with 17.2% more COVID-19 deaths and 31.6% more cases in England. The ecological design of our regional and local authority-level analysis likely led to exposure misclassification - this is common when using ambient monitoring network data. To minimise the potential for ecological bias, we combined air pollution data from available ambient sensors with local, individual-level information from the UK BioBank. This online repository contains detailed medical information for over 500.000 individuals across the UK, providing a powerful resource to analyse risk factors associated with COVID-19 outcome. Our models identified PM2.5 and PM10 as significant predictors of increased SARS-CoV-2 infectivity among the 1.450 UK BioBank participants that were tested for COVID-19 by May 2020, after controlling for the confounding effect of multiple socioeconomic and sociodemographic variables.

Our results are consistent with similar work carried out by teams in the USA 2,3 and Europe 4,5 where links between air pollution and COVID-19 fatalities were also reported. The take-home message from these different teams is that high levels of pollution may be an important contributor to coronavirus-related deaths. The studies mentioned above suggest a powerful link (correlation) between air pollution and the numbers and severity of COVID-19 cases. We must stress that correlation does not always mean causation; factors additional to air pollution may contribute to the spread and severity of the disease. However, our findings raise concern regarding UK air quality, as the pandemic continues.  Our data suggest that continuing to reduce pollution levels may assist strategies for dampening the impact of the virus on human health after we ease the lockdown. As for mechanisms explaining how pollution could affect the propagation and lethality of COVID-19, at the moment we can only speculate. It is plausible that pollution increases susceptibility to life-threatening COVID-19 infection - air pollutants irritate the lungs 6 - and reduce their defences against other causes of pneumonia 7. It is also possible that small pollution particles (called PM2.5) increase the number of ACE2 receptor (the binding site for SARS-CoV-2) in the lungs 8 and act as vehicles to transport the virus into the organ. This hypothesis is further supported by evidence suggesting that aerosols can carry live SARS-CoV-2 virus for several hours 9 from where it may be inhaled deep into the airways and establish infection. However, f it is important to caution that further work is required to determine the exact mechanisms linking air pollution to COVID-19.

With the improvements in air quality that have been recorded during the lockdown, it is possible that concomitant reductions in air pollution levels could attenuate SARS-CoV-2 infectivity and COVID-19 severity in the UK.

We hope this research will be useful in informing the decisions of policymakers. Please do not hesitate to ask any further questions you might have. Also, a video summary of this research is available on YouTube, here.

Yours, sincerely,

Co-signed by Marco Travaglio, Yizhou Yu, Rebeka Popovic, Nuno Leal, Liza Selley

References

1              Travaglio, M., Yu, Y., Popovic, R., Leal, N. S. & Martins, L. M. Links between air pollution and COVID-19 in England. medRxiv, 2020.2004.2016.20067405, doi:10.1101/2020.04.16.20067405 (2020).

2              Liang, D. et al. Urban Air Pollution May Enhance COVID-19 Case-Fatality and Mortality Rates in the United States. medRxiv, 2020.2005.2004.20090746, doi:10.1101/2020.05.04.20090746 (2020).

3              Wu, X., Nethery, R. C., Sabath, B. M., Braun, D. & Dominici, F. Exposure to air pollution and COVID-19 mortality in the United States. medRxiv, 2020.2004.2005.20054502, doi:10.1101/2020.04.05.20054502 (2020).

4              Sasidharan, M., Singh, A., Eskandari Torbaghan, M. & Parlikad, A. K. A vulnerability-based approach to human-mobility reduction for countering COVID-19 transmission in London while considering local air quality. medRxiv, 2020.2004.2013.20060798, doi:10.1101/2020.04.13.20060798 (2020).

5              Conticini, E., Frediani, B. & Caro, D. Can atmospheric pollution be considered a co-factor in extremely high level of SARS-CoV-2 lethality in Northern Italy? Environmental Pollution, 114465, doi:https://doi.org/10.1016/j.envpol.2020.114465 (2020).

6              Kelly, F. J. & Fussell, J. C. Air pollution and airway disease. Clin Exp Allergy 41, 1059-1071, doi:10.1111/j.1365-2222.2011.03776.x (2011).

7              Selley, L. et al. Brake dust exposure exacerbates inflammation and transiently compromises phagocytosis in macrophages. Metallomics 12, 371-386, doi:10.1039/c9mt00253g (2020).

8              Lin, C. I. et al. Instillation of particulate matter 2.5 induced acute lung injury and attenuated the injury recovery in ACE2 knockout mice. Int J Biol Sci 14, 253-265, doi:10.7150/ijbs.23489 (2018).

9              van Doremalen, N. et al. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. N Engl J Med 382, 1564-1567, doi:10.1056/NEJMc2004973 (2020).