10 worst in the United States and Canada
PM2.5 annual mean, micrograms per cubic metre
amount
control
Visalia-Porterville California 18
Hanford-Corcoran California 16
Portola California 16
Fresno California 15
Elkhart-Goshen Indiana 15
Regina Canada 14
Madera California 14
Lancaster Pennsylvania 13
Lebanon Pennsylvania 13
Lemhi Idaho 13
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