Fine pollution particles (PM2.5) may be responsible for 1.5 million additional premature deaths around the globe each year, according to a study which found that low levels of air pollution are more dangerous than previously thought.

The World Health Organisation's most recent estimates are that over 4.2 million people die prematurely each year due to long-term exposure to fine particulate outdoor air pollution referred to as PM2.5.

The latest study, published in the journal Science Advances, suggests that the annual global death toll from outdoor PM2.5 may be significantly higher than previously thought.