WorldA growing crisis at an aerospace plant in southern California involving a storage tank at risk of exploding has many wondering what exactly the hazardous chemical inside the tank is.Side-effects from exposure to liquid's vapour range from skin and eye irritation to respiratory issuesCBC News · Posted: May 23, 2026 5:18 PM EDT | Last Updated: 1 hour agoListen to this articleEstimated 2 minutesThe audio version of this article is generated by AI-based technology. Mispronunciations can occur. We are working with our partners to continually review and improve the results.Water is sprayed during a chemical incident involving a leaking tank of methyl methacrylate, a flammable liquid used in the aerospace industry, forcing an evacuation in the surrounding area, in Garden Grove, Calif. on May 23, 2026. (David Swanson/Reuters)A growing crisis at an aerospace plant in southern California involving a storage tank at risk of exploding has many wondering what exactly the hazardous chemical inside the tank is. The storage tank holding between 22,700 and 26,500 litres of methyl methacrylate overheated on Thursday and began venting vapours into the air at an aerospace plastics facility in Garden Grove, a city in Orange County, the county's fire authority said.Methyl methacrylate is used to make resins and plastics. The U.S. Environmental Protection Agency says the chemical, which usually appears as a clear liquid, is highly flammable.If it heats up, it can release a vapour that is harmful to people's health, said Orange County health officer Dr. Regina Chinsio-Kwong. California governor declares state of emergency due to overheating chemical tank40,000 people under evacuation orders in California amid chemical tank leakPotential side-effects from being exposed range from irritation to the skin and eyes to more serious respiratory and neurological issues, according to the U.S. Environmental Protection Agency (EPA). Respiratory symptoms can include chest tightness, shortness of breath, coughing and wheezing. Inhalation has also been shown to cause headaches, lethargy and lightheadedness.Long-term exposure has been linked to cardiovascular disorders, though the chemical hasn't been proven to cause cancer in humans, the EPA says. As of Saturday afternoon, emergency crews were still trying to cool the tank down to prevent it from either cracking and leaking, or exploding. The incident has led to evacuation orders for tens of thousands of people in southern California.With files from The Associated Press