A preliminary study has found the first evidence of a link between higher levels of air pollution and deaths from Covid-19 in England.
The analysis showed London, the Midlands and the north-west had the highest levels of nitrogen oxides and higher numbers of coronavirus deaths.
The research has not yet been peer-reviewed and shows only a correlation. The scientists behind the study said more research was needed to confirm a causal link and rule out other possible factors such as income levels and any difference in age profiles in the regions.
But they said there was an urgent need to share information about the pandemic. Previous research showed air pollution increased deaths during the Sars outbreak in 2003, and long-term exposure to dirty air is well known to damage lung health.
“Our study adds to growing evidence from northern Italy and the US that high levels of air pollution are linked to deadlier cases of Covid-19,” said Miguel Martins, of the University of Cambridge, who led the new analysis.
“This is something we saw during the Sars outbreak back in 2003, where long-term exposure to air pollutants had a detrimental effect on the prognosis of 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.”
Research published on Monday found that the five most polluted regions among 66 analysed in Italy, Spain, France and Germany accounted for 78% of all Covid-19 deaths in the 66 regions. Another recent study looked at fine particle pollution in the US and found that even small increases in levels in the years before the pandemic were associated with far higher Covid-19 death rates.
Experts say the idea that air pollution may increase susceptibility to Covid-19 is plausible, but they warn that early studies must be treated very carefully.
“As epidemiologists we are very cautious about interpreting studies, as we have learned even in high-quality studies about hidden biases and simple random variability,” said Prof Mark Goldberg, of McGill University in Canada. “When we try to assess causality, especially in non-randomised studies, we need about 20-30 really good studies.”
People over the age of 60 or with underlying health conditions such as cardiovascular disease, diabetes and chronic respiratory disease are thought to be at the highest risk of severe symptoms or death from Covid-19.
In the new study, the scientists write: “Long-term exposure to air pollutants, including nitrogen oxides from car exhaust fumes or burning fossil fuels, is a known risk factor for these health conditions.”
The analysis showed a correlation between air pollution levels recorded in 2018 and 2019 and data on deaths reported in England up to 8 April. “Future and more detailed studies may further elucidate these observations by addressing potential confounders, including socioeconomic status, comorbidities, age, race and differences between regional health regulations and their intensive care unit capacities,” the scientists said.
The study also notes that the severity of another lung infection, called respiratory syncytial virus, is known to be directly linked to variations in nitrogen oxide levels.
Prof Jonathan Grigg, of Queen Mary University of London, said it was important to note that the study was not peer-reviewed. “But these provisional results are compatible with recently published studies and confirm what we already know – that air pollution has many adverse effects on human health. We must therefore now plan to prevent a bounceback in traffic emissions after the lockdown has ended.”
Widespread lockdowns around the world have led to reduced vehicle traffic and air pollution. However, long-term exposure to dirty air before the pandemic may be more important than current levels of pollution.