Cut particulate air pollution, save lives

At a population level, reducing ambient fine particulate matter air pollution improves mean survival. This is a bold statement as it implies a causal effect for an exposure that is ubiquitous, involuntary, and cannot be randomly allocated to study participants. Nonetheless, the linked study by Chen and colleagues (doi:10.1136/bmj.n2368) adds to a now compelling body of evidence, and could serve as the coup de grâce that ends criticism of this statement.1

Fine particulate matter (PM_2.5) consists of airborne solid and liquid particles of less than 2.5 µm diameter that arise from both natural and anthropogenic sources.2 The small size of PM_2.5—a fraction of the width of a human hair and much smaller than mould and pollen—enables it to deposit deep within the lungs.3 From there, PM_2.5 can promote the release of proinflammatory mediators or vasculoactive molecules from lung cells, disrupt the autonomic nervous system’s regulation of the heart, and potentially translocate directly into the systemic circulation.4

More than two decades of observational evidence suggests that raised …