The health effects of fine particulate air pollution

Fine particulate matter (PM) of diameter less than 2.5 microns (PM_2.5) is ubiquitous, emanating especially from transport and combustion sources. Since a seminal 1993 study showing a clear association between airborne PM_2.5 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 PM_2.5—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 PM_2.5 exposure, but improved modelling of PM_2.5 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.

PM_2.5 has been associated with diseases of the respiratory and cardiovascular systems, with cardiovascular disease likely occurring through systemic inflammation and possibly translocation of particulate matter into the circulation.6 Indeed, ultrafine particles (<100 nanometres in diameter) have been found in the brain and heart.78 These mechanisms indicate that effects are not limited to respiratory and cardiovascular systems, but uncovering new …