Prolonged air pollution exposure is known to raise risk of several health conditions from respiratory to cardiovascular diseases.

But, a new study showed that hospitalised Covid-19 patients who had been chronically exposed in their neighbourhoods to higher particulate matter - such as smoke, soot, and dirt -- had increased risks for admission to the intensive care unit (ICU) and death compared to those without such exposure.

The findings, reported in the American Journal of Respiratory and Critical Care Medicine, showed that chronic exposure to particulate matter, even at levels below current regulatory thresholds, was associated with an 11 per cent higher risk of mortality and 13 per cent higher risk of admission to the ICU.

Exploratory analyses suggested that younger people of colour may be particularly susceptible, said Mount Sinai-led researchers.

The researchers noted that chronic air pollution exposure can alter the pulmonary immune system, may increase systemic inflammation, and can be associated with increased risk for cardiovascular disease and metabolic syndrome.

"The Covid-19 pandemic has brought to the forefront the critical role of the environment on health disparities. These data suggest that long-term exposure to air pollution is associated with higher Covid-19 morbidity and mortality amongst hospitalised patients," said Alison Lee, Assistant Professor of Medicine and Pediatrics, at the Icahn School of Medicine at Mount Sinai.

"Critically, air pollution is a modifiable risk factor. Policies to reduce air pollution must be considered a necessary public health measure, especially in communities that are disproportionately susceptible to air pollution's deleterious effects," Lee added.

A team of researchers conducted a retrospective analysis of more than 6,500 Covid-19 patients admitted to seven New York City hospitals with ethnically diverse patient populations amid the first peak of the pandemic from March to August 2020.

The researchers estimated exposure levels to pollutants including particulate matter, nitrogen dioxide, and black carbon at the residential addresses of the patients at the time of admission.

The team then assessed patient outcomes including mortality, ICU admission, and intubation.

"Being able to better understand what and how environmental factors play a role in health and Covid-19-associated risks not only allow us to better treat patients in the long-term, but also give us the opportunity to advocate for broader changes that can help prevent serious illness in the future," said co-author Stanley Pierre, Director of the Clinical Centres of Excellence Development Programme.