The study, which was published in the Proceedings of the National Academy of Sciences, found that if vehicles had been emitting 2008 levels of air pollutions during this time period, the death total in 2017 would have been 2.4 times higher than it was (48,200, or a 74% increase, rather than 19,800). The study emphasized that decades of air pollution regulation have contributed to many benefits here in the US, but noted that vehicle emissions are still a climate and public health issue.
The study used a combination of counterfactual scenarios, the latest epidemiological evidence, and detailed spatial resolution to analyze recent health benefits related to changes in fine particulate matter (PM2.5) and climate benefits of on-road emission reductions during this time period.