Authorities were scrambling to find a safe resolution as a damaged tank at a Southern California aerospace facility containing a hazardous chemical used to make plastic parts prompted an evacuation order affecting thousands of residents.The storage tank at GKN Aerospace with 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 over the weekend the tank could leak all the chemical or even explode if it overheats.No injuries have been reported, but more than 50,000 residents were under an evacuation order over the Memorial Day weekend. Firefighters were constantly spraying the tank with water in an effort to cool the chemicals heating up inside and prevent an explosion. Why is this chemical dangerous?Methyl methacrylate is a flammable, colorless liquid used in the production of resins, plastics and plastic dentures and is a hazardous substance regulated by the federal government. The substance can irritate the lungs, eyes and skin and in high doses can cause reduced lung function, along with dizziness and memory problems, according to the Environmental Protection Agency. Air monitoring tests have so far found that air pollution around the evacuation zone is within normal limits.