A newspapers vendor wears a surgical mask in smog-covered Mexico City on May 3, 2016 Mexico City officials issued a new air pollution alert yesterday, meaning that 40 percent of vehicles will be banned on Tuesday, while industries will be required to cut emissions. The alarm was raised after ozone levels reached 161 points, above the 150 level. The threshold was lowered from 190 to 150 last month. / AFP / YURI CORTEZ (Photo credit should read YURI CORTEZ/AFP/Getty Images)
