COVID-19 cases, deaths increase with air pollution - study finds

Researchers have found "compelling" evidence that air pollution significantly increases coronavirus infections and deaths.

The University of Birmingham has released a new study analysing the transmission of COVID-19 in the Netherlands where air pollution is worse in many rural areas than cities.

The research indicates that a small increase in people's long-term exposure to pollution particles raises infections and hospital admissions by around 10 percent and deaths by 15 percent.

"Our analysis used COVID-19 data up to June 5, 2020, capturing almost the entire known course of the Dutch epidemic," the study's authors wrote for The Conversation UK

"Our results provide compelling evidence of a statistically significant positive relationship between air pollution and COVID-19 cases, hospital admissions and deaths."

They said the relationship continues after taking into account contributing factors including age, health, income, and population density.

"What I was struck by was this really was a strong relationship," researcher Prof Matthew Cole told The Guardian. 

Cole said the study is more detailed and comprehensive than previous studies, including one by Harvard University researchers.

"We used data at much finer resolution, with the average size of the 355 Dutch municipalities being 95 square km compared to the 3,130 square km for a US county," he said.

"This means we can more precisely capture each region's characteristics, including pollution exposure."

Experts have lauded the study as "the best to date".

"As analyses of a possible link between air pollution and COVID-19 progress we are beginning to see much better studies emerge," said Prof Frank Kelly, at Imperial College London told The Guardian.

Prof Francesca Dominici, who led the Harvard Study, also praised the work as "very good", saying the research is important as each country's data has its own strengths and weaknesses. 

"Air pollution is not yet getting enough attention because of the slow peer-review process [for academic studies]," she said. 

"But hopefully as this and other studies are published, the topic will get more attention and most importantly will affect policy."

However the researchers said region-level data can only get them so far and more analysis is needed.

Pollution levels can vary from place to place making it difficult to be precise about the relationship between COVID-19 and air pollution, they said.

"Until detailed individual-level data is available providing information on COVID-19 and a wide range of other individual characteristics the statistical evidence will remain suggestive, perhaps strongly suggestive, but not conclusive."