The chemical industry has been well aware of the risks of the type of thermal runaway reaction that forced 50,000 people from their homes in Orange County last weekend, reviving years of warnings from researchers about the potential dangers.<\/p>\n
Nearly 15% of incidents in the U.S. involving uncontrolled chemical reactions between 1980 to 2001 were thermal runaway incidents that involved rapid polymerization of a chemical, according to a study<\/a> published in the journal ACS Omega, citing information from the U.S. Chemical Safety and Hazard Investigation Board. <\/p>\n Such incidents have led to deaths globally, but some experts say the industry has struggled to improve safety. <\/p>\n In Orange County, the crisis was sparked by thousands of gallons of a highly toxic chemical in a failing pressurized chemical tank that was heating up at a Garden Grove aerospace firm. There was a potential of fire or flash fire over many city blocks, and there were businesses, dozens of homes and an elementary school in a potential damage blast zone. <\/p>\n The worst-case scenario was averted over the Memorial Day weekend. But serious questions remain over how such a near-disaster could have happened. <\/p>\n Authorities suspect that the cooling system responsible for maintaining the temperature of a tank filled with a hazardous chemical at GKN Aerospace failed, leading to the crisis at the facility that triggered evacuations, Orange County Fire Authority Interim Chief TJ McGovern said Tuesday.<\/p>\n This likely led to a buildup of heat in the pressurized tank filled with 7,000 gallons of a highly reactive liquid chemical called methyl methacrylate, or MMA, which can be used to make items such as Plexiglass as well as household goods. <\/p>\n \u201cWe don\u2019t know why, but it stopped cooling,\u201d McGovern said Tuesday. \u201cSo that\u2019s what started this event, to where the product heated up and it off-gassed through the relief valve, and that\u2019s how this whole response started. We\u2019re just now being able to get to the tanks, so there\u2019s definitely more to come of what caused it.\u201d<\/p>\n Fire officials and experts were faced with a seemingly no-win situation: a \u201cboiling liquid expanding vapor explosion,\u201d or BLEVE, which would have caused widespread damage and released toxic material into the air, or a potential chemical spill that could have fouled up waterways and the ocean. Inhaling MMA can irritate the lungs and, at high levels of exposure, can cause severe respiratory distress and hospitalization; long-term exposure has been linked to serious organ damage. <\/p>\n Although fire officials referenced the off-gassing of \u201cfumes\u201d and said on Friday that the tank was \u201cno longer purging any kind of product,\u201d the county\u2019s health officer, Dr. Regina Chinsio-Kwong, on Monday said<\/a> no fumes or vapors were issued during the incident. The U.S. Environmental Protection Agency said its air monitors had not detected toxic airborne chemicals, but environmental experts were skeptical<\/a> that no toxic substances had been released. <\/p>\n The suspected failure of a cooling system, and the introduction of heat to a pressurized tank with MMA, planted the seeds of a potential catastrophe. <\/p>\n When liquid MMA is exposed to heat or light, it will start a chain reaction, said Elaine Villanueva Bernal, a lecturer at Cal State Long Beach\u2019s department of chemistry and biochemistry.<\/p>\n As MMA solidifies, \u201cit produces heat, and then in producing that heat, it furthers the chain reaction, so it keeps going and going and going,\u201d Bernal said. <\/p>\n If it gets out of control, this leads to a process called a thermal runaway. <\/p>\n MMA is a highly reactive chemical, a monomer that can be used to make polymers of hard, durable, lightweight and transparent plastics. But introducing heat to MMA in a pressurized tank caused the chemical to react, starting its transformation from a liquid to solid state, which produces even more heat. <\/p>\n Eventually, it can result in a BLEVE. <\/p>\n That refers to when a liquid is \u201crapidly depressurized, causing a nearly instantaneous transition from liquid to vapor with a corresponding energy release,\u201d and is \u201coften accompanied by a large aerosol fireball,\u201d according to the American Institute of Chemical Engineers\u2019 Center for Chemical Process Safety. <\/p>\n Chemical leak at GKN Aerospace<\/p>\n The Garden Grove facility neighbors an elementary school and residential neighborhood.<\/p>\n GKN Aerospace, based in Britain, makes landing gears, jet engines and other materials for commercial and military aircraft at its Garden Grove facility. The company did not respond to questions Tuesday, but earlier said that \u201cwe apologize for the ongoing disruption this incident is causing and our priority remains its safe resolution.\u201d <\/p>\n Orange County ended up in a much better position than incidents elsewhere. In India, 12 people died<\/a> and more than 580 were injured after a thermal runaway of styrene and release of styrene vapor occurred at the LG Polymers plant in the port city of Visakhapatnam in 2020. A committee appointed by India\u2019s top environmental court blamed \u201cgross human failure\u201d and a lack of basic safety norms for the disaster, the Associated Press reported<\/a>. <\/p>\n \u201cLessons have not been learned,\u201d the ACS Omega study said, referring specifically to styrene-related runaway incidents. <\/p>\n And in 2012, one person died and 36 were injured in an explosion and chemical fire at a chemical plant in Himeji, Japan. The disaster occurred after the \u201crunaway polymerization of acrylic acid\u201d in an intermediate storage tank, a study<\/a> published in the journal Process Safety and Environmental Protection said, citing information from the factory\u2019s operator, Nippon Shokubai Co.<\/p>\n A study published in 2023 urged more attention to be paid to MMA. <\/p>\n \u201cThe correct choice of operating conditions often constitutes the first line of defense against thermal runaway events,\u201d the study, published<\/a> in the journal Thermochimica Acta, said. Without evaluating potential thermal hazards, implementing safe process designs and strengthening thermal safety, \u201cthe highly exothermic nature of the reaction may pose a severe threat to process safety as well as to industrial-scale equipment and to human lives.\u201d <\/p>\n