Calif., national groups split on secondhand smoke

By John Ritter

SACRAMENTO — California regulators, the first to brand secondhand smoke an air pollutant, are convinced it causes breast cancer in younger women. But they're butting heads — at least for now — with conventional wisdom in the cancer research establishment.

Major national groups — the American Cancer Society, the National Cancer Institute, the Centers for Disease Control and Prevention — won't endorse the California Environmental Protection Agency's unprecedented finding, adopted last week by the state's Air Resources Board. (Related: California links passive smoke, breast cancer)

Though a secondhand smoke link to breast cancer is "certainly possible," says Michael Thun, the cancer society's vice president of epidemiology, "at this point, there is not broad scientific consensus."

According to Jonathan Samet of Johns Hopkins University, senior scientific editor of a U.S. surgeon general's report on secondhand smoke due this year, "The scientific community is still watching for the evidence to evolve."

Other researchers say these organizations are too cautious and should consider newer, more rigorous studies that did a better job of measuring women's exposure to secondhand smoke.

"The authors of this report explain why the previous studies have been inconsistent and really make a compelling case," says Andrew Hyland, a researcher at Roswell Park Cancer Institute in Buffalo.

'Warning to young women'

Nancy Evans, health science consultant for the Breast Cancer Fund in San Francisco, and other advocates for breast cancer research say young women shouldn't be denied information about these risks. It's accepted that secondhand smoke causes lung cancer and heart disease, but women under 50 can think of them as diseases of old age.

"There's enough awareness about breast cancer that this would be a real strong warning to young women," Evans says. CalEPA's report found that waitresses have the most workplace exposure to secondhand smoke. Breast cancer kills 40,000 U.S. women a year.

The Air Resources Board has a history on the cutting edge. Its directives since the 1960s to cut tailpipe pollution forced automakers to make cleaner vehicles. Automakers have sued the board over a 2004 decision to require greenhouse gas reductions. The board was the first agency, before the surgeon general, to identify secondhand smoke as a cause of heart disease.

"That was treated with similar skepticism," says Cheryl Healton, president of the anti-smoking American Legacy Foundation.

The board won't decide whether to adopt tougher restrictions on secondhand smoke until a study of costs and consequences is done. Lawyers are researching whether the board has the authority to ban smoking in cars when children are present. A 1999 law requires the board to pay special attention to children's heath risks.

Some skeptics of CalEPA's findings point out that if tobacco smoke causes breast cancer, the risk for active smokers should be much higher than for women exposed to secondhand smoke. It isn't.

The cancer society's Thun, in his comments on the CalEPA report filed with the air board, said "lack of an association with active smoking weighs heavily against the possibility" that secondhand smoke could raise breast cancer risk.

One theory on the apparent discrepancy is that smoking damages ovaries and cuts estrogen production, but secondhand smoke exposure doesn't, says Melanie Marty, the CalEPA scientist who supervised the report. Lower estrogen levels have been shown to reduce breast cancer risk.

Newer studies that kept women exposed to secondhand smoke out of control groups did find elevated breast cancer risk among active smokers, the report noted.

It also seems counterintuitive that younger women would be more at risk than older women, who presumably have been exposed to secondhand smoke longer. Risk was elevated as much as 120% for younger women but hardly at all for women past menopause, the CalEPA analysis found.

It's not clear why. What's known is that a woman's greatest susceptibility to carcinogens is between puberty and her first baby. In addition, there's evidence genes and family history play a role: women who are more likely to develop cancer get it at a younger age, says Laura Esserman, a researcher at the University of California-San Francisco who studies breast cancer biology.

More advanced studies

Twenty years ago, the surgeon general found that secondhand smoke causes lung cancer. Evidence today that it causes breast cancer is even stronger, says Stanton Glantz, a professor of medicine at the University of California-San Francisco and a member of the scientific panel that reviewed CalEPA's report.

"There are more studies, the risk estimates are more consistently elevated, and they're higher than they were for lung cancer," Glantz says. "Plus, there's all these toxicology studies and molecular biology they didn't have back then."

Public health groups' reluctance to embrace CalEPA's findings shows "very serious bias against new information," Glantz says. "It's a ridiculously conservative position."

Findings in a forthcoming surgeon general's secondhand smoke report aren't public. But "an active line of research" is whether younger women have a higher risk of breast cancer, says Terry Pechacek, associate director for science in the CDC's office on smoking and health. He wouldn't comment on CalEPA's report because he said that might reveal some of those findings.

"There's no need to be cautious," Esserman says. "Get the information about risk out there and let women be the judge of whether it's important or not. For goodness sake, there's about 10 other good reasons to avoid secondhand smoke anyway, right?"