About 23,000 pounds of a flammable, foul-smelling toxic gas leaked from the DuPont chemical plant in La Porte where four workers died earlier this month, the company said Saturday.
That’s significantly more than the 100 pounds of methyl mercaptan that DuPont estimated had escaped the plant in its initial report, and was enough to asphyxiate the four workers and hospitalize another.
Companies are required to report all releases of at least 100 pounds of the gas to the Texas Commission on Environmental Quality. DuPont said it revised its initial estimate after determining how much gas was in the plant’s pipes and vessels before and after the tragedy.
“The release occurred inside a process building at the site’s Crop Protection unit and dissipated from openings in that structure over time,” the company said in a statement.
The U.S. Chemical Safety and Hazard Investigation Board is still investigating the incident.
Methyl mercaptan can cause nausea, vomiting and fluid buildup in the lungs. Its rotten-egg smell wafted over La Porte for at least 24 hours after the accident, but county health officials said the leak posed little risk to the community because the gas rapidly degrades once released into the air. Even trace amounts carry the smell.
The plant, about 30 miles southeast of Houston, makes products like alcohol resins and a popular insecticide called Lannate.
In the past five years, the TCEQ has cited it at least two dozen times for violating state law. The plant has failed to perform routine safety inspections, keep equipment in proper working order and prevent unauthorized pollution leaks, according to violation notices issued by the agency. In a few instances, the agency demanded fines of a few thousand dollars from DuPont for more serious lapses.
But the unauthorized leaks of toxic chemicals are common in Texas. Thousands — and even millions — of pounds of toxic chemicals beyond what permits allow have spewed from the state's facilities, as The Texas Tribune has reported. Though many of those events were close calls that prompted evacuations at worst, some triggered deadly explosions that, in turn, caused even more gas to be released.
Since 2009, Texas chemical manufacturers have reported at least 19 other unauthorized releases of methyl mercaptan, according to state data. DuPont’s was the only methyl mercaptan release that killed or injured workers during that period.