Dangers from damaged California chemical tank persist. Here’s what to know

Authorities scrambled to find a safe solution when a damaged tank at a Southern California aerospace facility containing a dangerous chemical used to make plastic parts triggered an evacuation order affecting thousands of residents.

GKN Aerospace’s storage tank containing about 6,000 to 7,000 gallons (22,713 to 26,498 liters) of methyl methacrylate overheated last week and began leaking vapors into the air around Garden Grove, a city in Orange County. Officials said this weekend that the tank could leak all of the chemical or even explode if it overheats.

No injuries were reported, but more than 50,000 residents were under evacuation orders over Memorial Day weekend. Firefighters doused the tank with water to try to cool the chemicals heating up inside.

Methyl methacrylate is a colorless, flammable liquid used in the production of resins, plastics, and plastic dentures and is a federally regulated hazardous substance. According to the Environmental Protection Agency, it can irritate the lungs, eyes and skin and, in high doses, cause decreased lung function, as well as dizziness and memory problems. Tests have revealed that air pollution in the evacuation zone is within normal limits.

The reservoir’s drainage valves are not working, officials said, adding that without action there could be either a large chemical spill or an explosion.

Firefighters focused on keeping the tank temperature below 85 degrees F (29.4 degrees C) to relieve pressure. On Sunday, EPA chief Lee Zeldin said the most likely scenario was a “low volume release” of the tank’s contents, so authorities could “monitor, neutralize and contain the threat.”

If the temperature inside the tank increases, the pressure will increase as the methyl methacrylate changes from a liquid to a gas, increasing the risk of an explosion, which could ignite other tanks on site.

An explosion that releases the chemical would send it into a wider area and could create vapors that are dangerous to inhale, according to Orange County’s top health official, Dr. Regina Chinsio-Kwong.

Chinsio-Kwong said if people inhale the vapor, it could cause irritation to the eyes, nose and lungs and cause a sore throat, burning eyes and even dizziness. She said the chemical had a fruity odor, but smelling it did not mean a person would have health effects.

In prolonged cases, exposure to methyl methacrylate can cause serious breathing problems or render a person unconscious. The evacuation zone is west of Anaheim, home to the two Disneyland theme parks, which were not under evacuation orders. Chinsio-Kwong said people outside the evacuation zone do not need to worry about health impacts.

Authorities said Sunday that the tank had a crack, which could reduce the risk of an explosion. Capt. Wayhowe Huang of the Orange County Fire Department said the tank did not appear to be releasing toxic chemicals into the atmosphere.

Elias Picazo, a chemistry professor at the University of Southern California, said that a “strategic leak allows more time for the liquid in the tank to solidify” and that a leak could be used “to direct unreacted liquid out of the tank in a controlled manner.”

Zeldin said a controlled, low-volume release of the chemical would allow authorities to relieve pressure on the reservoir. GKN Aerospace said on Sunday it was continuing to work with local authorities.