The Centre for Science and Environment (CSE) in New Delhi stated that over 3 tonnes of styrene gas leaked into the air from one of the storage tanks at the LG Polymers factory in Visakhapatnam and quickly spread into nearby areas on Thursday. The think-tank issued a fact sheet after assessing the gas leak tragedy, which has left at least 11 persons dead and scores hospitalised.
CSE stated that while oxygen needs to be given as immediate treatment to those affected by the toxic gas, residents living near the plant need to be evacuated as long-term exposure can be detrimental to their health.
“Also, as styrene reacts to form styrene dioxide, the air could remain contaminated for some time. However, the winds blowing from the sea could also help to disperse the gas,” the report said.
Detailing how the disaster happened, CSE said that there was a temporary partial shutdown at the chemical plant due to the lockdown with only maintenance work taking place.
“Styrene monomer was being used at the manufacturing plant to produce expandable plastics. The storage requirement of styrene monomer says that it should be stored strictly at a temperature below 17oC,” it said.
However, CSE noted that the styrene gas was not being stored at the appropriate temperature.
“This caused pressure to build up in the storage chamber and led the valve to break, resulting in the gas leakage,” reads the fact sheet. CSE also observed other issues including that the container used to store styrene gas was old and not properly maintained. “This non-maintenance of the facility resulted in the leakage of 3 tonnes of styrene into the surrounding areas,” it stated.
While styrene is a likely carcinogenic substance, CSE explained that when it reacts with oxygen in the air, it mutates into styrene dioxide which is more lethal. The gas which can stay in the air for weeks, can cause symptoms including eye irritation, breathing difficulties, nervous system symptoms such as headaches, weakness, depression, CNS dysfunction. Individuals can also experience hearing loss and numbness or tingling in hands and feet. Large amounts of styrene exposure can also cause people to fall into a coma.
Dr Thava Palanisami, professor, Global Centre for Environmental Remediation (GCER) & CRC for Contamination Assessment and Remediation of the Environment (CRC CARE), University of Newcastle, Australia, “Styrene can stay in the air for weeks. It is highly reactive, it can combine with oxygen to form styrene dioxide which is more lethal. The presence of other pollutants can also affect the reactivity. On a sudden note operating one reactor in full load can also lead to such disasters.”
CSE concluded its fact sheet with an advisory: “This shows us that there are ticking bombs out there as the lockdown ends and industries start resuming activities. Therefore, an immediate directive must go to all units to ensure safety while resuming operations -- in case the lockdown continues, these safety precautions must not be negated,”
LG Polymers issues statement
Meanwhile, Mohan Rao, the Managing Director of LG Polymers, issued clarification about what caused the gas leak.
“There needs to be continuous movement in the styrene tank which has to be maintained at a specific temperature. We have refrigeration and monitoring systems for this purpose. At least 15 individuals, including security and operating managers, are present each shift who keep a watch over this. There are two tanks, with the capacity to hold 5000 tons, it was one of the tanks which had the issue,” he said to media personnel adding that the tanks must be maintained at a temperature of 20 degrees centigrade.
He further explained that in addition to styrene there are hydrocarbons in the storage tanks, which normally do not mix with the gas, and are present in a separate layer above the gas in the tank.
“The vapours from the hydrocarbons have polymerized on the roof of the tank and then fallen back into the tank. This occurred due to lack of movement in the tank combined with the UV light which fell over the tank during the lockdown period,” he says.
Polymerisation is a process by which small molecules react together to form a bigger chain of molecules, called a polymer. In this particular incident, photopolymerisation occurred, which means that the UV light (from the sun) caused the reaction.
“Typically there are certain chemical inhibitors added to control this reaction, however there was stagnation of the substances inside the tank due to the lockdown which caused this reaction to occur,” he said, “We weren’t able to enter the tank in the morning, even when I came, no one could go inside. Now after the inhibitors have been added continuously for 5 hours, we are able to go near the tank. All our people are also inside trying to handle this issue.”
He further added that clearance would be given once officials were confident that there were no more vapours being released from the tank. Following this the people who were evacuated from nearby villages would be allowed to return to their homes.
“The tank capacity is 2400 tons, but now there is only 1800 tons of substance inside the tank,” he said, “There has never been any residual material [causing photopolymerization] in the tank all these days, this is the first time this has happened because there has been stagnation due to the lockdown.”