Dust and soot in the air contribute to between 20 and 200 early deaths a day across 20 of the largest cities in the U.S., according to a new study by researchers at Johns Hopkins University published in the New England Journal of Medicine. The new report, the largest coast-to-coast study of the problem, found health problems occur even in cities that meet national air quality standards. The Clinton administration set a tighter standard for particulates in 1997, but industry groups are challenging the rule in the Supreme Court, saying it was based on weak science. The new report seems to strengthen the administration’s argument, although it will have no bearing on the case.