Smoking & Cancer (Contd.)

Ever since Dr. Ernest L. Wynder championed the view that heavy cigarette smoking is a major cause of lung cancer, he has been challenged to produce the substances in tobacco smoke (or tar) that do the damage. Last week the American Association for Cancer Research, meeting in Atlantic City, took Wynder's word for it that he has now run the number of tobacco-tar fractions capable of causing cancer up to eight, with the end not yet in sight.

Working with Dr. Dietrich Hoffmann at Manhattan's Sloan-Kettering Institute, said Dr. Wynder, he has found in the tar no fewer than 17 hydrogen-carbon compounds of the polycyclic group (i.e., with several carbon rings in the molecule). Nine have been exonerated, but to the six already known to produce cancer on the backs of mice the Wynder-Hoffmann team has added two more--3.4-benzfluoranthene and 10.11-benzfluoranthene. But these chemicals occur only in minute quantities in cigarette tar.

These amounts, Dr. Wynder conceded, are not enough to explain the recent startling increase in lung cancer. So, he argued, either there are other cancer-causing substances still undetected, or there is something that may seem innocent by itself but increases the effect of these cancer-stimulating factors. Laboratory research is now aimed at reducing the tar's content of polycyclic hydrocarbons, either by achieving more complete combustion or by adding a catalyst to the tobacco.

No smoker himself, Dr. Wynder despairs of persuading 55 million Americans to quit the habit. But to make it safer, he urges manufacturers to use low-tar tobaccos and the most potent filters they can find. For smokers themselves he recommends: try to cut down, inhale less, never smoke down to the butt--not more than half of a king-size cigarette--because 60% of the tar is in the last half.

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