The harder we look, the more we find

Fine particulate matter (PM) of diameter less than 2.5 microns (PM2.5) is ubiquitous, emanating especially from transport and combustion sources. Since a seminal 1993 study showing a clear association between airborne PM2.5 and mortality rates in six cities in the United States,1 many attempts have been made to quantify the global annual burden of mortality due to PM2.5—0.8 million in 2005,2 3.15 million in 2015,34 and almost 9 million in 2018.5 This increase reflects not a 10-fold rise in PM2.5 exposure, but improved modelling of PM2.5 concentrations, and use of real world exposure-response associations incorporating new data from developing nations, which has led to conclusions with increased reliability and, unfortunately, of increased mortality.

Photograph © Andrew Dunn [CC BY-SA 2.0 (], via Wikimedia Commons

Read more at BMJ…