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 all the available evidence on the effects of short-term exposure to particulate matter (PM) and nitrogen dioxide (NO2) (Orellano et al. 2020). Specifically, the research published updated quantified risk ratios for exposure to PM, NO2 and O3 on premature mortality (people dying earlier than they otherwise would have). They also assessed how this risk changed at different levels of exposure.