Making Cigarettes Safe?

Although the major cancer-causing substance in cigarette tar has not yet been identified, so much is now known about it that smoking could be rendered relatively harmless--without waiting for the substance to be isolated. This reassurance came last week from the man who, since his student days, has been busy amassing proof that heavy, long-continued cigarette smoking is the main cause of the recent dramatic increase in lung cancer: Dr. Ernest L. Wynder, 34, of Manhattan's Sloan-Kettering Institute.

Dr. Wynder told the American Association for Cancer Research, meeting in Chicago, that the villain is not present in tobacco leaves in their natural, unburned state. His research team proved this by extracting tar from cigarette tobacco without burning it: the resulting substance produced virtually no cancers when painted on the backs of mice. But batches of the same tobacco were burned at varying temperatures, and the tars extracted. Tar from the lower-temperature-burning ranges (560DEG to 720DEG C.) produced few or no cancers. From 800DEG to 880DEG C. the number of cancers increased sharply. Conclusion: evidently, the cancer-causing agent is the result of high-temperature combustion.

Tentative Conclusion. Could the original substance from which the cancer agent is formed be pinned down and removed from the tobacco? Wynder & Co. closed in on a natural waxy substance that is known to coat the tobacco leaf. In the wax are "aliphatic hydrocarbons.'' which, burned at high temperatures, produce "polycyclic hydrocarbons," and these in turn can cause cancer.

Working with the University of Toronto's Chemist George Wright, the researchers washed tobacco in hot hexane, which dissolves the wax. They extracted the wax and burned it alone. The resulting tar proved to be at least ten times as cancer-potent as ordinary tar from whole tobacco: in five months all mice painted with a 5% solution from tests at 880DEG had papillomas (precursors of cancer), and 27% had full-blown cancer. The tar from the wax contained all the cancer agents now known to exist in small amounts in cigarette tar, but Dr. Wynder doubts that these substances are the only cause of the lung-cancer increase, suspects there are others in the tar. One tentative conclusion: dewax the tobacco to make it less harmful. Dr. Wynder did not say what cigarettes would taste like if made from dewaxed tobacco. (He has tried them, but being a nonsmoker, he is a poor judge.)

Other Possibilities. Wynder also saw hope for making the cigarette safer along several other lines. One is to reduce the temperature at which a cigarette burns, now in the 800DEG-880DEG C. range, to a heat now shown to be relatively harmless--around 767.DEG the average temperature at which tobacco burns in a pipe. (This might be done either by adding a chemical to the tobacco, or--more likely--by changing the cut to resemble that of pipe tobacco.)

Another way would be to develop a filter that would remove at least 40% of the tar. Present filters, said Dr. Wynder. remove too little of the tar--and they let the cancer agent pass as freely as the rest of the smoke. Dr. Wynder's willingness to settle for a 40% filter is based on statistics: among two-pack-a-day smokers the incidence of lung cancer every year is 278 per 100,000; for men who smoke only half a pack to a pack for the same 20 years or more, the incidence is only 61. A 40% filter would bring most men's tar intake down to the equivalent of well under a pack a day.

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