University of Cambridge study finds link between high levels of air pollution and deadlier cases of Covid-19
A preliminary study by a team of scientists at the University of Cambridge has found a link between high levels of air pollution and the deadlier cases of Covid-19.
Researchers at the MRC Toxicology Unit in Cambridge have found an association between certain air pollutants and Covid-19 in England.
They analysed the data on total Covid-19 cases and deaths against the levels of three major air pollutants, collected in 2018 and 2019 when no Covid-19 case was reported.
The study used publicly available data from seven regions in England where a minimum of 2,000 infections and 200 deaths were reported between from February to April 8, 2020.
The largest number of Covid-19 deaths in England have occurred across London and the Midlands, which reflects the geographical distribution of the virus, and previous studies had shown that the annual average of nitrogen dioxide concentrations are largest in the two regions.
When the scientists compared the annual average of daily nitrogen oxide and nitrogen dioxide levels to the total number of Covid-19 cases in each region, they found these to be positively correlated – in other words, the higher the pollutant levels, the greater the number of Covid-19 cases and deaths.
Both nitrogen oxide and nitrogen dioxide result from a chemical reaction between nitrogen and oxygen during combustion of fossil fuels, and therefore represent a significant source of air pollution in areas with high traffic.
Marco Travaglio, a PhD student at the MRC Toxicology Unit, said: “Our results provide the first evidence that SARS-CoV-2 case fatality is associated with increased nitrogen oxide and nitrogen dioxide levels in England.
“London, the Midlands and the North West show the largest concentration of these air pollutants, with Southern regions displaying the lowest levels in the country, and the number of Covid-19 deaths follows a similar trend.”
The team found a negative association between ambient ground levels of ozone and the number of Covid-19 cases and deaths in each region – in other words, reduced ozone levels are associated with a greater number of Covid19 cases and deaths.
Ozone is a secondary by-product of traffic-related air pollution and is generated through sunlight-driven reactions between motor-vehicle emissions and volatile organic compounds. The lowest levels of ozone were found in highly-urbanised regions, such London or the Midlands.
This is likely to be due to the highly-reactive nature of ozone, which results in the gas being converted to other chemicals, a phenomenon previously reported for areas of heavy traffic.
The researchers suggest that the detrimental effects of low ozone concentration observed in this study could be linked to increased generation of ozone oxidation products.
Dr Miguel Martins, senior author on the study, said: “Our study adds to growing evidence from Northern Italy and the USA that high levels of air pollution are linked to deadlier cases of Covid-19.
“This is something we saw during the previous SARS outbreak back in 2003, where long-term exposure to air pollutants had a detrimental effect on the prognosis of SARS patients in China.
“This highlights the importance of reducing air pollution for the protection of human health, both in relation to the COVID-19 pandemic and beyond.”
Researchers have published their report on MedRXiv because of the need to share information relating to the coronavirus pandemic, although it has not yet been peer reviewed.
It was added that the findings only show a correlation and that further research is needed to confirm that air pollution makes Covid-19 worse.