Do We Really Need Another Time-Series Study of the PM2.5-Mortality Association?

The link between particulate pollution and mortality was originally recognized in the context of severe episodes of poor air quality in the 20th century, such as the London Fog of 1952.(1) These episodes showed clear evidence that the number of deaths increased in association with high levels of particulate matter (PM). The policy response to the increasing evidence of the effects of air pollution on public health was for governments to develop air-quality regulations. In the United States, the Clean Air Act of 1970 mandated that the Environmental Protection Agency (EPA) develop national ambient air-quality standards (NAAQS) to protect even . . .