Martinez Refining Company released toxic dust into nearby communities early Tuesday, Contra Costa County health officials said.
Officials identified the substance as “coke dust" or petroleum coke, a byproduct of refining, and said it was visible on the ground in neighborhoods near the refinery.
Petroleum coke can “can affect the heart and lungs and cause serious health effects” if inhaled, according to the Environmental Protection Agency.
Residents are advised to avoid breathing or close contact with the toxic substance, but there is "no immediate respiratory health risk" presented by the coke dust, as the dust has settled and is not made airborne easily unless it is “seriously disturbed,” according to a Contra Costa Health Department spokesperson.
The health department said they have not received any reports of illness in connection with the toxic dust release as of Tuesday afternoon, and that the dust release began around 8:30 a.m., lasting roughly one minute.
Martinez Refining Company refines diesel, gasoline and jet fuel, according to its LinkedIn page.
The refining company had notified the nearby residents via the Community Warning System early Tuesday.
The Bay Area Air Quality District is monitoring the dust release and investigating complaints. It advised residents to follow instructions from local health officials.
Contra Costa County health officials recently launched a cleanup operation of several streets and a train station after mercury spilled from a city cleaning crew truck. Officials believe the mercury was dumped in a trash can on May 8.