London, Jun 21 (IANS): Exposure to air pollution, even at low levels, meant an average of around four extra days in hospital for Covid-19 patients, further increasing the burden on health care systems, according to two studies.

The first study, published in the European Respiratory Journal, showed that 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 the second study, also published in the same journal, researchers found that long-term exposure to pollution at levels well below current limits increased the risk of contracting Covid-19, being hospitalised and dying of the disease.

The first study led by a team from the Hasselt University in Belgium included 328 patients who were hospitalised for Covid between May 2020 and March 2021.

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. They also measured the amount of soot in the patients' blood.

Their findings showed that 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.A

Researchers found that higher levels of soot in the patients' blood increased the likelihood of needing intensive care treatment by 36 per cent.

"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," said Professor Tim S. Nawrot from Hasselt University.

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 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.

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

"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. Cleaner air would make populations more resilient to respiratory infections, seasonal epidemics, and major pandemics in future,"Andersen said.