Question: Mary Ochsenhirt Amdur studied the effects of which historic air inversion that killed 20 people?
Sentence (from "1948 Donora smog"): The 1948 Donora smog was a historic air inversion that resulted in a wall of smog that killed 20 people and sickened 7,000 more in Donora, Pennsylvania, a mill town on the Monongahela River, 24 mi southeast of Pittsburgh.
Relevant evidence: Yes