The Garden Grove Chemical Leak: What Is Methyl Methacrylate and What To Do If You Are Exposed?

GARDEN GROVE, CALIFORNIA - MAY 23: An aerial view of water being sprayed onto an overheated 34,000-gallon tank at GKN Aerospace on May 23, 2026 in Garden Grove, California. A malfunctioning tank at an aerospace plant has the potential of a chemical leak or explosion. An incident at GKN Aerospace, a manufacturer of components for commercial and military aircraft, triggered the facility's automatic sprinkler system. Investigators are expected to examine the cause of the hazardous leak once the site has been fully stabilized. (Credit: Photo by Apu Gomes/Getty Images)

GARDEN GROVE, Calif. — When firefighters arrived at the GKN Aerospace facility on Western Avenue last Thursday afternoon, they found a 34,000-gallon storage tank overheating with no clear way to stop it. Inside: approximately 7,000 gallons of methyl methacrylate, a highly toxic, flammable, and volatile industrial chemical used to manufacture acrylic glass and aircraft components.

Five days later, more than 50,000 Orange County residents remain under mandatory evacuation orders. A state of emergency has been declared. The federal government has stepped in. And the crisis — on one of the most consequential holiday weekends of the year — is not over.