WASHINGTON — Federal officials probing last month's gas leak at a Union Carbide plant in Institute, W. Va., said Wednesday that they are testing to determine whether methyl isocyanate, the chemical linked to last December's disaster in Bhopal, India, was present in the storage tank in which the Institute accident occurred.
Environmental Protection Agency officials, who termed the tests "routine," said they do not currently dispute Union Carbide's finding that no methyl isocyanate was in the Institute pesticide factory's reactor tank when it overheated on Aug. 11, spewing toxic gases. A total of 135 persons was sent to local hospitals as a result of the chemical leak.
'Derivatives' of Gas
However, they acknowledged, Union Carbide's own analysis of the Institute accident indicates that at least 225 pounds of the 3,800-pound leak were "derivatives" of methyl isocyanate--molecules of the substance glued together by heat or reaction with other chemicals.
Union Carbide contends that those derivatives were among 300 pounds of "general crud" lodged in plant equipment from past processes, EPA investigators said.
Among other matters, the federal tests could help determine whether the derivatives were the manufacturing leftovers that the company contends they were or, instead, were evidence that liquid methyl isocyanate was part of the chemical soup in the tank at the time of the accident.
"At this point, our labs are still trying to figure out what was there," James Makris, deputy director of the EPA's hazardous response division, said. "We're testing for anything that could possibly be" in the tank.
OSHA Analyzing Residues
Makris said the Occupational Safety and Health Administration also is analyzing gas leak residues for methyl isocyanate and other chemicals.
The two searches for methyl isocyanate "shouldn't raise any eyebrows," the EPA said, because the tank in which the accident occurred apparently was once used to manufacture pesticides based on methyl isocyanate.
Union Carbide's explanation of the Institute leak has wavered from initial suggestions that the gas released was mostly aldicarb oxime, an "irritant," to later admissions that the largest component was methylene chloride, an irritating solvent and a possible carcinogen. Throughout, however, the firm has maintained that none of the leak involved methyl isocyanate, the gas that killed more than 2,000 persons near Union Carbide's Bhopal factory.
In an Aug. 23 analysis of the Institute leak, the company said that about 300 pounds of the chemical release consisted of "residue that had been attached to the inside of the vent pipe header," part of the complex's piping system.
Carbide did not identify the nature of those chemicals. However, Makris said that at least two substances that Union Carbide termed residue--150 pounds of trimethyl isocyanurate and 75 pounds of 1,3,5-trimethylbiuret--are in fact methyl isocyanate "triamers," or molecules of methyl isocyanate bound together in triplets.
EPA experts said that the methyl isocyanate triamers could have been solids that did not drift far when blown out of the Institute tank and pipes, and that Union Carbide's explanation that they were residues is plausible.
But Ellen Silbergeld, a molecular biologist with the Environmental Defense Fund in Washington, said the presence of triamers could equally suggest that methyl isocyanate was in the tank and changed its chemical structure when the tank was accidentally heated for a week, as Union Carbide spokesmen say occurred.
Carbide Blamed Citizens
Separately, Union Carbide Chairman Warren M. Anderson suggested Wednesday that his firm is not solely to blame for apparent safety shortcomings cited in the wake of the Institute accident.
In remarks to New York securities analysts, he said that Union Carbide has conducted fire drills at the site to prepare residents for emergency evacuations but that "nobody came."
"There's been a total lack on the part of the community about helping themselves," he said. "They don't have their act together."
He added: "Nobody's ever been killed in the Kanawha Valley (in West Virginia) because of our products."
Times Staff Writer Paul Richter, in New York, contributed to this story.