Already known for having some of the worst air quality in the U.S., people in Southern California are now also at risk of inhaling smoke.

Los Angeles is now a week removed from the day that multiple devastating wildfires erupted to torch tens of thousands of acres. But still, the question remains if people should wear masks to limit their exposure to toxins in the air.

Ash from the recent LA County fires and burn scars formed by other wildfires in the fall can be dispersed by strong winds. See an air quality map.

Calculating air pollution from wildfires and other events has become more complicated. That doesn’t mean it’s necessarily more accurate.

Smoke from the raging Southern California wildfires is filling city skylines, causing officials to warn residents of poor air quality.

Los Angeles officials on Thursday told most evacuees from the wildfires to stay away from their homes at least another week. This is as emergency responders remove toxic waste from incinerated neighborhoods and cut off electricity and gas lines posing a hazard amid the ruins.