When the Scale Runs Out
The U.S. Environmental Protection Agency's Air Quality Index has five categories. The worst is "Hazardous," which begins at 301. At that level, the EPA's own guidance states: "Everyone is likely to be affected."
The U.S. Environmental Protection Agency's Air Quality Index has five categories. The worst is "Hazardous," which begins at 301. At that level, the EPA's own guidance states: "Everyone is likely to be affected."