TEXAS CITY, Tex. – After 4,000 people were evacuated as a result of a leak of hydrofluoric acid from a refinery, questions are still being asked about potential hazards here and in other cities where the same chemical is used.

Those questions center both on the long-term effects on those exposed to the Oct. 30 leak from the Marathon Petroleum Company here and on the degree of risk faced by workers and residents living near 68 plants around the country where the potentially lethal chemical is used. More than 1,000 residents were treated for eye and respiratory problems after a pipeline ruptured here, sending a cloud of gas into nearby residential neighborhoods.

Much of the concern here stems from charges by an environmental group that officials here and in other communities have not adequately alerted people to dangers posed by the chemical, which is used as a catalyst in refining. At news conferences here and in Washington, the Environmental Policy Institute compared the leak’s potential peril to the accident at Bhopal, India, where more than 2,500 people were killed after a 1984 gas leak. Fred Millar, a spokesman for the group, said that if the accident had released hydrofluoric acid in its more concentrated liquid form instead of as a gas, the accident could have killed thousands. The institute said the evacuation here was inadequate given the risks involved.

Comparison Is Disputed

Marathon officials said a release of hydrofluoric acid had never resulted in a fatality and that the comparison with Bhopal was overblown and inappropriate. ”It’s obvious this was an entirely different situaton than Bhopal,” said a Marathon spokesman, Ira Winsten. ”I question the motives of anyone who would try to make that comparison.”

But fears have spread in a community largely dependent on the refineries that make up the town’s economic base. ”We want to be prepared next time,” said Cathy Burd of the new group Keep Citizen Safe. ”We’ve always been afraid, but now it’s getting so bad I won’t let them alone.”

Doctors Are Optimistic

Marathon tried to allay fear by presenting its own physician, a local doctor and a Mexican doctor who said there was little chance that residents exposed to the accident would suffer any long-term effects.

Dr. Miguel Trevino of Matamoros, Mexico, said he had studied workers affected by far more severe exposure in a 1980 accident and found no lasting effects.

”Taking into consideration the lesser severity of the signs and symptoms observed in the Texas City patients, there is no reason to assume that any long-term effects will occur,” he said.

But local health officials said that, in the absence of published scientific studies of exposure to similar leaks, a study of local residents was needed.

”My own feeling is that we know painfully little about the long-term effects of exposure,” said Dr. Marvin S. Legator, director of the division of environmental toxicology at the University of Texas Medical Branch at Galveston. He said the biggest questions concerned effects on children.

Liquid Is Called Peril

More worrisome here and elsewhere is the question of risks posed by a liquid leak of hydrofluoric acid. Mr. Millar, citing a 1986 research study on toxic gases, said the dangers of a liquid leak are far greater than was originally believed. He said that 6 million to 12 million Americans in cities such as Houston, Los Angeles, Chicago and Philadelphia could be endangered by such a leak.

Dr. Ronald Koopman, program leader for liquified gaseous fuels at the Lawrence Livermore National Laboratory, who conducted the tests in the 1986 study for the Amoco Corporation, said the results were alarming and should be considered by industry and regulatory officials. He shied away from a Bhopal comparison but said the Texas City accident could have been worse, with considerable loss of life. Marathon officials said they were reviewing engineering controls but said there had been no risk of a liquid spill.

Officials in Texas City, scene of America’s worst industrial accident, the 1947 explosion that killed 576 people, said the town’s emergency response system had been ranked among the nation’s best and that living with dangerous chemicals was a way of life there.

”This thing got blown out of proportion by people coming in here and saying, ‘What if,’ ” said Texas City’s emergency management coordinator, George Stapleton. ”This is not a resort town. This is industry.”

Dr. J. W. O’Bryant, a local physician who treated victims of the leak, agreed that the people may have overreacted. But when asked whether people should be living as close as they are to the local refineries, he paused and said, ”That’s a good question.”