t is hard to believe there is anything new to be learned about the evils of tobacco. But a depressing new analysis by a team assembled by the World Health Organization has found that tobacco is a lot more dangerous than anyone previously realized, whether one smokes it directly or inhales the fumes expelled by someone else.

The panel of 29 experts from a dozen countries was formed by the International Agency for Research on Cancer, the W.H.O. unit charged with assessing cancer risks. The analysis is billed as the most comprehensive assessment of smoking hazards ever and will be published shortly. It examined more than 3,000 studies conducted since 1986, the last time the W.H.O. group carried out a systematic review. In the interim, lifetime smokers in the industrialized world have had plenty of time to contract new cancers and a huge volume of studies has added to the accumulating knowledge of tobacco's toxicity.

One disturbing finding was that tobacco smoke causes cancer in many more parts of the body than previously demonstrated. We've long known that smoking causes cancers of the lung, oral cavity, bladder and certain other organs. Now it has been shown to trigger leukemia and cancers of the stomach, liver, cervix and kidney as well.

Equally troublesome is a firm conclusion, based on more than 50 studies, that secondhand smoke put into the air by smokers can harm even innocent bystanders who have never smoked a cigarette in their lives. Such passive smoking boosts their risk of lung cancer by about 20 percent, especially if they have experienced prolonged exposure from working or living with smokers. The experts could not yet determine whether children exposed to secondhand smoke in the womb or after birth face an increased risk of cancer as adults, but parents are on notice that their poisonous exhalations are potentially dangerous.

This bleaker-than-ever view of tobacco's harmful impact makes it imperative that campaigns be accelerated to curb smoking not only in the industrialized world, where death rates are high, but also in the developing world, where the tobacco industry has increasingly focused its marketing might. The new analysis provides added reason to ban smoking from public places and workplaces around the world. Continued exposure to the fumes is both obnoxious and potentially hazardous.