A study published in Nature has found that levels of fine particulate matter (PM 2.5) in the US dropped by around 70% over the 35 years between 1981 and 2016, from a combination of less polluting power plants and cleaner vehicles, spurred by more stringent regulations and the shift, mostly from financial considerations, from coal to natural gas firing. Perhaps unsurprisingly, however, the areas that were most polluted in 1981 continued to tend to be the most polluted across the study period, and these tended to be areas of lower income. The study will strengthen the case for the benefits of environmental regulation, but is also broadly heartening news.