The relationship between long-term exposure to air pollution and Covid-19

The UK Prime Minister’s recent backtracking on the country’s commitment to several key environmental schemes has brought the topic of green policies back to the top of the news agenda. Much of the focus has been on climate change and the effects of increased temperatures and more extreme weather on the habitability of our planet in the long-term, but it is important to also consider the shorter-term impacts that air pollution can have on human health.

Earlier this year, public health researchers in Belgium and Denmark published separate studies which showed that long-term exposure to air pollution contributed to an increased risk of serious or severe health outcomes in Covid-19 patients. The results of these studies were reported in the Guardian, as well as some more industry-specific websites such as E&T and Eos.

Reporting on the associations and causal effects between pollution and health can be incredibly challenging, but all three articles did a good job of clearly outlining what was actually found within the studies, without any attempt to sensationalise the outcomes. In all cases, a clear effort was made to incorporate aspects of the results in the authors’ own words, which vastly reduces the risk of anything being misinterpreted.

The Guardian article did an excellent job of explaining the wider context around these papers, and in particular provided a nice explanation about the distinction between longitudinal (long-term) studies, which track groups of individual patients, and ecological studies which use data averaged from the whole population. Previous studies on this topic had fallen into the latter category, while the two published here were both longitudinal, and the author did a good job of outlining why these represent more significant and more powerful results. It can be challenging to explain these concepts in a national newspaper, and I felt their explanation was clear and concise without oversimplification or losing any detail.

My only small criticism of this article was the reference to pollution having “aged” patients, something which was included both in the headline and the opening paragraphs. The interpretation behind this statement was not entirely unreasonable, it was based on a finding in the Belgian article that patients who had been exposed to air pollution spent a similar length of time in hospital with Covid-19, as people 10 years older – “These effect sizes…were equivalent to the effect of a 10-year increase in age on hospitalisation duration”. It is perhaps understandable that this line was used in order to give the reader some useful context, but I think the word “aged” could confuse readers about the actual effects of pollution – neither study makes any claim about pollution actually physically aging our bodies.

The other two articles were clearer in their explanation of this part of the results – the E&T author wrote “the size of the effect of air pollution on time spent in hospital was equivalent to the effect of a ten-year increase in age”, while the Eos article quoted an author “To put it very simply, a 40-year-old with high air pollution [exposure] and a 50-year-old with low air pollution [exposure] are at about the same risk”. Both of these approaches are more true to what was actually reported in the journal article.

All three articles did a good job of outlining the potential implications of these findings – and although both articles were based on Covid-19 hospitalisations and deaths, similar effects are likely for other respiratory illnesses including seasonal flu. Both the Guardian and E&T directly quoted an author “Reduction of air pollution should be at the heart of preventive measures for current and future pandemics, as well as a strategy for dealing with seasonal influenza pandemics”, while Eos used a similar quote which stressed the importance of governments acting on emissions.

These were three great examples of high-quality scientific writing, in each case they summarised the results clearly, leaned on the original papers whilst adding useful and relevant context for readers, amplified the voices of the actual authors of the work, and provided insight into the wider implications of the research. Educating the public on the impacts of pollution and climate change has never been more important, and articles of this quality play a crucial part in doing so.