Where is the dirtiest air in the world now?

In three major cities in the United States, shrouded in smoke from massive wildfires, air quality is now worse than anywhere else on the planet.

Portland, Seattle and San Francisco have the worst air quality of any major city in the world, according to IQAir, a group that monitors the world’s air quality. The air in Seattle and San Francisco is so smoky that it is at hazardous levels according to the Air Quality Index. “Everyone can begin to experience some adverse health effects, and those in the most sensitive groups can experience more serious problems,” experts say.

In Portland, Oregon, things are much worse. The air here is now such that anyone who breathes it “could experience serious health effects.” Therefore, all residents have to stay indoors and reduce their activity level.