With air pollution a distant memory outside some pockets in the United States (or during wildfires), the U.S. EPA oddly embraced one paper, which they had not seen any data for(1), claiming that particles so small they could only be detected with an electron microscope, 2.5 microns in size, were killing people.Data didn't show it, but it doesn't matter and that is the great thing about modern epidemiology. In this decade, epidemiologists only need to show a statistical correlation and then they get media coverage and hand it off to scientists and tell them to prove it. It's sort of like theoretical physicists claiming they can show time travel or a multiverse and the incompetent noobs in experimental physics need to drop everything and prove them right.