SEOUL -- A group of American physicians has urged the South Korean government to permit research into the medical effects of tear gas, saying that its "massive" use by police in June and July may have harmed many Koreans.

The doctors, from the Boston-based Physicians for Human Rights, conducted what appeared to be the first assessment by health professionals of the consequences of tear gas used liberally here to control demonstrations. They said the tear gas caused "widespread suffering" among many innocent civilians.

"Serious and painful acute illnesses have been caused, sometimes with permanent impairment of health," Dr. Jonathan E. Fine, executive director of the group, said Saturday after a one-week visit here. "Long term chronic illness may result in some cases."

The physicians' group campaigns against torture and what it considers other cases of human rights abuses around the world.

The group documented a handful of cases of permanent injury caused by the tear gas, mostly eye damage and wounds caused by shrapnel from exploding tear-gas grenades. One student was fatally injured when he was struck in the head by a tear-gas canister.

The doctors said many others may have been permanently affected. It is possible that the gas may aggravate, or even cause, long-term lung disease and other serious conditions in some victims, they said.

The government has refused to identify the chemical agents it uses and has not permitted Korean health professionals to study the effects of the gas, Fine said.

"This society will never be able to assess the damage done until it does proper studies," he said, adding that several doctors here had proposed such studies but were discouraged from undertaking them by the government. "There's an awful lot that isn't known when such huge quantities are used."

Police have said they set off more than 351,000 canisters and grenades of tear gas during antigovernment demonstrations between June 10 and 27, or more than 20,000 per day. Much of the gas was dispersed in downtown areas, where it wafted into stores, hotels and subway stations, affecting many bystanders.

The government has said that tear gas, while unpleasant, is a more humane way to control crowds than the more lethal weapons used by police forces in other nations. During the violent June demonstrations, three people died: the student whose head was injured, a policeman run over by a bus and a bystander who fell off a bridge.

"In developed countries, the police use not only tear gas but also billy clubs and even firearms," President Chun Doo Hwan said during a June conversation with Cardinal Kim Sou Hwan. "We abolished the billy club a long time ago, and the police are trying to use defensive methods to put down demonstrations."

{After returning to the United States, Fine on Wednesday released recommendations made by the group. "We consider the use of these agents (tear gases) as tantamount to chemical warfare against civilians," he said, adding that they "should be banned from use against human populations everywhere."}

When asked what alternative form of crowd control his group would propose, Fine said, "We are physicians, we're not policemen . . . . We feel there have to be more imaginative and peaceful ways to resolve conflicts."

The group was able to obtain one compound used by police and send it to the United States for analysis. It turned out to be CS gas, a common tear-gas compound.

The analysis did not confirm common rumors here that the South Korean government has developed its own unusually strong brand of gas. However, the sample was pure CS gas, not the diluted substance that is sometimes used, and the doctors said other compounds may also have been used.

"It's really a misnomer to call this tear gas," said Bailus Walker Jr., former Massachusetts commissioner of public health and another member of the team. "It's really a poisonous substance, because the effects are far more harmful than just tearing."

Symptoms include burning and blistering of the skin, headache, tightness of the chest and a feeling of inability to breathe as well as painful burning of eyes, nose and throat, the doctors said. The gas drifted into hospitals where some asthma patients were especially affected, they said.

Even policemen were affected, although they wore helmets, gas masks and protective clothing, Dr. Howard Hu of the Harvard School of Public Health said. He said medical students reported treating riot policemen with skin burns around the edges of their masks and in underarm and groin areas.

Residents of affected neighborhoods said several children suffered cold-like symptoms for weeks.

"This really is an area calling for further study as to whether these people will develop chronic illness," said Dr. Paul Epstein of Harvard Medical School.

The survey trip was cosponsored by the American College of Physicians and the American Medical Student Association. Those groups had not read or endorsed the findings when the doctors were interviewed.