pollution levels in some national parks concentration in micrograms per cubic meter park sulfates* ozone** grand canyon -lrb- rim -rrb- 1.4 na shenandoah 11.1 291 acadia 4.9 345 yosemite 1.7 245 mesa verde 1.4 na crater lake 0.8 na great smoky mountains 10.4 228 mount rainier 2.8 97 u.s. health standard 0.2*** 235 # * 1989 summer average concentration ** 1988 highest hourly concentration ***natural background level established for eastern u.s. # national ambient air quality standard source : national park service