Summary

In 2021, the World Health Organisation (WHO) published revised recommendations for ambient air quality (WHO 2021). To support this update, WHO published a review paper in 2020 evaluating the best available evidence on the effects of long-term exposure to particulate matter (PM) (Chen & Hoek 2020). Specifically, the research published updated quantified risk ratios for exposure to PM on premature mortality (people dying earlier than they otherwise would have). They also qualitatively assessed how these risks changed at high and low exposure levels