- (B) Cities in China have the highest air pollution concentrations in the
world. The World Health Organization (WHO) upper safety level of PM 10 is
20 μg per m^3 . The city with the highest average PM 10 concentration in the
world is Ahvaz, Iran, with a concentration of 372 μg per m^3.
marvins-underground-k-12
(Marvins-Underground-K-12)
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