IN RECENT YEARS tobacco companies, concerned about the growing movement to restrict smoking in public places, have directed an increasing share of their advertising budgets to the nonsmoker. The companies propose in ads that the whole controversy be treated as a question of manners rather than one of cancer, emphysema and heart disease. If we are all just tolerant of our neighbor's right to smoke, the message goes, then smokers might be persuaded to forgo the habit during expensive meals, small closed-room conferences and tours of firecracker factories.

The latest series of advertisements, now appearing in full-page spreads across the country, seeks to allay the fears of abstainers -- two-thirds of the adult population -- who are justifiably concerned that the smokothers generate is harming them. Even the Tobacco Institute's own surveys show that a majority favors segregating smokers in trains, airplanes, theaters, restaurants, work places, offices and the like. And that majority has begun to speak up loud and clear. To counter this campaign the tobacco companies question the scientific basis for the fear, as they had for years disputed the surgeon general's findings on the dangers to smokers themselves. The complaints of nonsmokers, they imply, are unreasonable. It is, in fact, these "fears and phobias (that) can lead to ill health," we are told, so we should stop making "a medical problem out of a social one."

What do the scientists say? Surgeon General C. Everett Koop presented some persuasive testimony at a recent Senate hearing. In the last three years, he said, 15 published studies examined the link between passive smoking and cancer; only three did not show a statistically significant positive correlation between the two. While nonsmokers naturallyabsorb fewer carcinogens than smokers, there is evidence that those exposed only in the work place -- not at all at home -- suffer the same impairment of some breathing functions as light smokers. Abstaining spouses of smokers have had higher rates of lung cancer than similar spouses of nonsmokers. The surgeon general warns that more recent studies indicate that nonsmokers may also be at risk for developing heart disease from secondhand smoke.

Nonsmokers who want to breathe clean air are not finicky cranks, intolerant of the rights of others, as the tobacco company ads would lead you to believe. Their objections are well-founded, as the increasing weight of scientific evidence demonstrates. Believing industry claims that secondhand smoke is nothing to worry about could be dangerous to your health.