Nearly 2 million Californians live within 3 miles of a plant storing methyl methacrylate like GKN in Garden Grove

Nearly 2 million Californians live within 3 miles of a chemical plant using methyl methacrylate (MMA), the compound involved in the Garden Grove tank crisis over Memorial Day weekend, according to the U.S. EPA's Toxics Release Inventory.

A majority of those residents, or 1.6 million, are in Southern California, with roughly 117,000 living within a mile of such a facility in Los Angeles, Orange, and Riverside counties.

The close proximity of the GKN Aerospace plant to homes and schools led to widespread outrage and dozens of lawsuits after residents were displaced for days. First responders rushed to GKN on Thursday, May 21, after a pressurized storage tank containing 7,000 gallons of MMA began careening toward a dangerous leak or explosion.

Evacuation orders forced 50,000 people in Garden Grove and neighboring cities into shelters and hotels through Memorial Day weekend until Tuesday night, when the risk of explosion was averted, thanks in part to a crack in the tank.

Fourteen facilities in California used MMA heavily enough to make the Toxics Release Inventory list, collectively producing 333,518 pounds of MMA waste in 2024. Such plants are predominantly located in communities of color, with an average of 77% of residents within a mile identifying as such.

GKN topped the list, generating 131,779 pounds, nearly double its 2023 output and the largest increase in the plant's more than 30-year history. The company typically sends MMA waste to Arizona to be burned for energy.

GKN did not respond to questions about the increase.

The second highest waste generator, Tesla's Fremont plant, produced 115,136 pounds of MMA waste. About 2,200 people live within a mile of Tesla's facility, about 10 times less than those near GKN.

MMA is a widely used chemical that can self-react to form plastic, producing heat that can be controlled with inhibitors or release valves. Experts said such reactions happen more often than people think, but safety systems usually prevent escalation.

Even when systems fail, some tanks are designed to fail in benign ways, like the crack on GKN's tank.

Multiple investigations are underway. A failure in the tank's cooling system led officials to fear a "boiling liquid expanding vapor explosion" (BLEVE) that could cause massive damage and release a toxic, flammable plume.

Short-term MMA exposure causes respiratory and skin irritation; long-term effects are unknown. Michael Kleinman, an environmental toxicity professor at UC Irvine, said valves to introduce inhibitor or safely bleed MMA were inoperable during the crisis.

Kleinman called the incident a wake-up call for companies to review safety measures. Records from the South Coast Air Quality Management District show some plants have checkered pasts.

GKN was cited in 2014 for failing to submit a hazardous materials business plan, fined $2,550 in 2018 for not maintaining equipment, and paid over $900,000 in 2021 for emission record violations.

Other plants also have violations. Plaskolite West in Compton was cited five times since 2003, including for an MMA leak in March 2022 that caused hundreds of odor complaints.

About 9,000 people live within a mile of Plaskolite. Sechrist Industries in Anaheim had no AQMD violations.

Engineered Polymer Solutions in Commerce, a Sherwin-Williams subsidiary, was accused by the EPA in 2021 of failing to perform daily checks on a chemical tank and having excessive volatile organic compounds; it paid a $306,426 penalty. Interplastic in Hawthorne received eight AQMD violation notices in two decades, including a 2025 notice for operating without a valid permit.

Arkema Coating Resins in Torrance had no AQMD violations; a spokesperson said the company continuously monitors storage and conducts regular emergency drills.

The GKN incident and a separate chemical tank rupture that killed 11 in Washington state sparked renewed calls for stronger regulations. Last year, the EPA proposed repealing a 2024 rule that tightened safeguards against chemical releases, arguing it threatened national security.

Environmental advocates argue the rule protects residents and should be strengthened. MMA is not currently regulated under the Risk Management Plan.

"Every single chemical evacuation or lockdown shows a strong need for EPA to fully implement and build on the Safer Communities Rule," said Emma Cheuse, an environmental attorney with Earth Justice.