"Most polluted census tracts in 1981 remained the most polluted in 2016 despite nationwide reductions in pollution, study says".
"Wealthy white Americans are still getting to breathe cleaner air than lower-income communities of color, despite significant nationwide reductions in pollution since the 1980s, according to a new study.
Fine particle pollution – which is 2.5 micrometers or smaller – has fallen an average of about 70% since 1981. But air pollution is not equally distributed around America.
In general, the gap between communities with the cleanest and dirtiest air has narrowed. Still, the already disadvantaged parts of the US continue to have the worst air."