Claims that smoking a cigarette is twice as dangerous for a woman as a man are backed up by experiments on lung tissue, says a UK expert. But other researchers say the evidence is inconclusive.

Diane Stover of the Sloan-Ketting Cancer Center in New York presented a large-scale review of data on sex, smoking and lung cancer to delegates at the American Thoracic Society conference in San Francisco on Monday. "A cigarette smoked by a woman had double the carcinogenic effect as a cigarette smoked by a man," she concluded. David Phillips, a lung cancer expert at the Institute of Cancer Research in London, says: "I would agree with that. The idea that women are at greater risk of lung cancer from smoking is not universally accepted. But it's a plausible picture, and we've done experimental studies that back this up." However, Clive Bates of the London-based campaign group Action on Smoking and Health disagrees. "This is interesting, but the evidence is inconclusive. The conclusion of most epidemiologists is that if women smoke like men, they die like men." DNA damage Phillips' team studied lung tissue from men and women. They found that women who had smoked the same number of cigarettes as men showed twice the amount of DNA damage to their lungs. The reason is unclear. But women have higher levels than men of a key enzyme that metabolises certain carcinogens in the lungs and converts them into a more dangerous form, Phillips says. It is possible that levels of the enzyme, cytochrome P4501A1, are affected by female hormones such as oestrogen, he adds. However, not all cancer researchers accept the idea. "So far, the studies have been quite small. Some researchers think they need more replication," says Phillips. Correspondence about this story should be directed to latestnews@newscientist.com

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