What is methyl methacrylate? Chemical inside Garden Grove tank and its effects on humans, animals

GARDEN GROVE, Calif. (KABC) -- The toxic chemical leaking from a large storage tank in Garden Grove is methyl methacrylate, or MMA - a highly hazardous substance that can pose significant health and safety risks depending on exposure, officials said.

Methyl methacrylate is used to produce shatter-resistant acrylic glass, paints, adhesives, resins and plastics. Authorities describe it as both highly toxic and highly flammable, with the potential to become explosive under certain conditions.

Orange County fire officials said the incident involves a large volume of the chemical, with estimates of up to 7,000 gallons spilling from the tank. The Orange County Fire Authority noted that incidents involving this type of chemical are rare, with limited case studies available to guide response efforts.

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"It's a respiratory irritant, so it can start off very mild, but it can progress to a point where, yes, you would probably require hospitalization, if not more," said Division Chief Nick Freeman of the Orange County Fire Authority.

Health experts say exposure can occur through inhalation or direct contact. Short-term exposure may irritate the skin, eyes and respiratory system, while higher concentrations can cause more severe effects.

"At very high levels, it can really cause severe respiratory distress and hospitalization, and this is where we really need everybody to heed all the evacuation orders," said Orange County Deputy Health Officer Dr. Regina Chinsio-Kwong.

Officials emphasized that MMA vapor is heavier than air, meaning it can settle closer to the ground if released, increasing the risk in surrounding areas.

First responders are also monitoring for the possibility of a hazardous airborne plume, though its size and concentration remain uncertain.

"We don't know, we don't know in terms if there was a plume, how heavy of a plume and concentration of the substance would be in that plume," Chinsio-Kwong said. "If that were to happen, we want everybody to be away from the zone that we have created to safeguard everybody's health."

Doctors said the chemical's impact depends largely on the level and duration of exposure. In addition to lung and skin irritation, abrupt contact can potentially affect multiple organs, while prolonged or slow leaks could lead to longer-term health effects.

People who work with methyl methacrylate are typically required to wear protective equipment such as goggles and respirators due to its hazardous nature.

While research into long-term health effects remains limited, officials say methyl methacrylate is not currently considered carcinogenic.

The substance can also affect animals, including birds, though impacts may vary by species.
As of early Friday afternoon, officials said air quality levels were within normal limits, but monitoring is ongoing.

No injuries or deaths have been reported.

Authorities continue to stress the importance of following evacuation orders as crews work to contain the leak and prevent ignition, citing the chemical's flammability and the limited experience responders have with incidents of this scale.