DATA: OTHERS' SMOKE WORSE THAN FEARED.

Byline: Denise Grady The New York Times

Secondhand cigarette smoke is more dangerous than previously thought, Harvard researchers are reporting today in a study with broad implications for public health policy and probable direct impact on at least one major lawsuit.

The 10-year study, which tracked more than 32,000 healthy women who never smoked, has found that regular exposure to other people's smoking at home or work almost doubled the risk of heart disease.

Many earlier studies have linked secondhand smoke to heart disease, but the new findings show the biggest increase in risk ever reported, and the researchers say it applies equally to men and women.

The women in the study, who ranged in age from 36 to 61 when the study began, suffered 152 heart attacks, 25 of them fatal. The results mean that ``there may be up to 50,000 Americans dying of heart attacks from passive smoking each year,'' said Dr. Ichiro Kawachi, an assistant professor of health and social behavior at the Harvard School of Public Health and the lead author of the study, which was published in the journal Circulation.

By contrast, lung cancer deaths from passive smoking are estimated to be far fewer, at 3,000 to 4,000 a year. Because heart disease is much more common than lung cancer, even a small increase in risk can cause many deaths.

Before this study, it was known that passive smoking caused increased risk for several ailments, including asthma and bronchitis, as well as middle-ear infections in young children. But the increased risk for heart disease had been estimated at about 30 percent.

``This is a very important study,'' said Dr. Stanton Glantz, a professor of medicine at the University of California at San Francisco, who has done extensive research on passive smoking but who was not involved in the Harvard study. ``It's exceptionally strong and from a very solid group.'' Glantz also praised the Harvard team for what he called its careful analysis of workplace exposure to smoke, which had rarely been done before.

``That's important because of the effort to create laws controlling smoking in the workplace,'' he said.

Although the federal Occupational Safety and Health Administration has proposed nationwide workplace rules, they are not yet in effect. Regulations vary by state or city.

``This study will be of enormous help to legislative bodies, statewide and locally, who are trying to get limits on smoking, especially in controversial areas like restaurants and bars, where the tobacco industry has worked closely with restaurant associations to block legislation to make these places go smoke free,'' said Edward Sweda, a senior lawyer with the Tobacco Control Resource Center at Northeastern University in Boston.

The study may be particularly pertinent for one lawsuit.

``From our standpoint, that's a wonderful study,'' said Stanley Rosenblatt, a Miami lawyer representing flight attendants in a class-action suit against tobacco companies that will go to trial June 2.

That suit is the first class-action suit based on the effects of secondhand smoke. The case ultimately could involve 60,000 former and current flight attendants, who will be seeking billions in damages, Rosenblatt said. The attendants contend they were harmed by smoke in airplane cabins when smoking was legal on most flights. Most of the plaintiffs have had lung cancer or respiratory ailments.

The Philip Morris Cos., which is named in the flight attendants' suit, declined to comment on the study. The Tobacco Institute, an industry group, said it could not comment on the study because it had not seen a copy of it.

The data being reported today are from the Nurses' Health Study, a project that began in 1976 with 121,700 female nurses filling out detailed surveys every two years about their health and habits. To measure the effects of passive smoking, the researchers asked the women in 1982 about their exposure, and then monitored new cases of heart disease for the next decade. The analysis did not include all the study participants, but only the 32,046 who had never smoked and who at the outset did not have heart disease or cancer.

The women who reported being exposed regularly to cigarette smoke at home or work had a 91 percent higher risk of heart attack than those with no exposure. Even though the women worked in hospitals, some were exposed to smoke on the job because at the time of the study many hospitals allowed smoking in certain areas. The study was set up to make sure that other risk factors like diabetes and high blood pressure did not account for the difference between the two groups.

Laboratory studies of the effects of passive smoke on the body support the survey findings, Glantz said.

In studies of both people and animals, Glantz and other researchers have identified several ways in which the chemicals in secondhand smoke can contribute to heart disease. Besides reducing a person's oxygen supply, the substances damage arteries, lower levels of the beneficial form of cholesterol known as HDL and increase the tendency of blood platelets to stick to one another and form clots that can trigger a heart attack.