Air quality in the San Francisco Bay Area in the United States reached 'unhealthy' levels on Wednesday, Sept. 20, officials warned, after smoke from multiple wildfires from Northern California and Oregon drifted into the region.

The air quality deteriorated to a point that the Bay Area Air Quality Management District upgraded its air quality advisory to a Spare the Air Alert. The alert bans "burning wood, manufactured fire logs or any other solid fuel, both indoors and outdoors."

The district said that the air quality is ‘unhealthy for sensitive groups’ and ‘unhealthy’ overall and that the smoke now contains a fine particulate matter known by the particles’ size as PM2.5, which can have a major impact on people’s health.

"After evaluating the current observations, also taking into account that the forecast model, we realized that we need to also alert the public and also just up the forecast a bit to the current conditions, which is actually unhealthy air that folks are breathing right now. That is expected to last through today and also into Thursday," said Duc Nguyen, the district's principal air quality meteorologist.

The origin of the smoke stems from the Pearch Fire, Blue Creek and Marlow fires, Bluff 1 and Mosquito fires, and Smith River Complex fire in California and the Anvil Fire in Oregon, Nguyen said.

The brunt of the impact on the Bay Area currently is south of the Golden Gate Bridge, Nguyen said.

(Production: Nathan Frandino)