Covid-19 patients with high air pollution exposure spent longer in hospital

According to researchers from Hasselt University in Belgium, the effect of pollution on patients’ time in hospital was equivalent to being a decade older. Conversely, the effect of reducing exposure to pollution was 40 to 80 per cent as effective in reducing patients’ time in hospital as some of the best available treatments.

In a second study, the researchers used data on all 3.7 million Danish people aged 30 or older to establish the impact of air pollution on Covid-19. They found that long-term exposure to pollution at levels well below current EU limits increased the risk of contracting Covid-19, being hospitalised and dying of the disease.

The research team used data on levels of three pollutants – nitrogen dioxide, soot and fine particles (PM2.5) – at the patients’ home addresses before they were hospitalised with Covid-19. They also measured the amount of soot in the patients’ blood.

The researchers compared this data with clinical outcomes, such as how long patients had to remain in hospital before they were well enough to go home and whether they were treated in intensive care. They also took account of other factors that are known to affect Covid-19 infection, such as age, sex and body-mass index.

People exposed to higher levels of fine particles and nitrogen dioxide in the week before they were hospitalised had to stay in hospital for more than four extra days on average.

Despite the fact that all levels of exposure were below the EU threshold, 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. The results also suggested that average exposure to higher levels of nitrogen dioxide and soot over the previous four years meant Covid-19 patients stayed longer in hospital on average.

Study leader, professor Tim S. Nawrot, said: “Our findings indicate that people who were exposed to air pollution, even at relatively low levels, were sicker and needed more time in hospital to recover. The pandemic placed an enormous strain on doctors, nurses and other healthcare workers. Our research suggests that air pollution made that burden even greater.”

Researchers in the second study used data from the Danish National Covid-19 Surveillance System from the first 14 months of the pandemic combined with detailed information on the levels of air pollution at people’s home addresses over the previous 20 years.

They found that increases in long-term exposure to nitrogen dioxide and fine particles, even at levels well below current EU limits, increased the risk of contracting Covid-19, being hospitalised and dying of the disease.

People living with certain medical conditions, such as heart disease, asthma, diabetes and dementia, and those from more deprived backgrounds were even more susceptible to the combined effects of air pollution and Covid-19.

Study author Dr Zorana Jovanovic Andersen from the University of Copenhagen, Denmark said: “These results show how air pollution can compromise our immune system and leave us vulnerable to Covid-19 and other respiratory infections.

“Reduction of air pollution should be in the heart of preventive measures for current and future pandemics, as well as a strategy for dealing with seasonal influenza pandemics. Cleaner air would make populations more resilient to respiratory infections, seasonal epidemics and major pandemics in future.”

A study last week found that humans inhale up to a credit card’s worth of microplastic every week, depending on where they live.