by Edi Lau and Dorsey Griffith
March 10, 2005
The findings, which go further in establishing the link between cigarettes and breast cancer than any before, are sure to be debated for months. But the draft study already has spurred discussion in the nation about regulating tobacco use in private venues such as cars.
"It's another indictment of tobacco and the health effects of secondhand smoke on healthy people, especially children," said Paul Knepprath, vice president for government relations with the American Lung Association of California.
"It provides an opportunity for California to continue its leadership in reducing exposure to the public."
The analysis was conducted by scientists at the Office of Environmental Health Hazard Assessment, a respected research arm of the California Environmental Protection Agency. The team considered the results of about 1,000 studies to come up with its conclusions.
The newest, most attention-getting finding is that exposure to secondhand smoke may increase a woman's risk of breast cancer nearly twofold. Though several earlier studies found no such link, the researchers said that recent and better-controlled studies consistently identified elevated risk, particularly in younger women.
"What this really does say is that tobacco smoke is a risk factor for breast cancer," said Melanie Marty, who led the team.
Oddly enough, smoking itself is not thought to elevate breast cancer risk. Marty said that may be because active smoking reduces levels of estrogen, a hormone in the body that fuels tumor growth.
"We think that partially mitigates the risk and confuses the picture," she said.
Inhaling smoke secondhand, however, may not significantly dampen estrogen levels.
Evidence of a link between breast cancer and tobacco was strongest among younger, pre-menopausal women. Dr. Scott Christensen, associate clinical professor of oncology at the University of California, Davis Medical Center, was not surprised. He said that during a woman's menstrual cycle, hormones cause cells to grow and divide, making their DNA more susceptible to cancer-causing damage.
Making associations between environmental toxicants and cancer is extremely difficult, Christensen added, because studies must involve large numbers of people and many years to be conclusive. "It's gratifying the work is being done," he said.
On average, women in the United States have a one in eight chance of developing breast cancer. "It's a complex disease, with lots of factors," Marty said. "This is just one of the factors."
Joel London, a spokesman for the U.S. Centers for Disease Control and Prevention, said the federal government would like to see more research into the possible link. "It will stimulate continued and accelerated scientific evaluation of the smoking and breast cancer issue," he said.
In addition to identifying an elevated risk for breast cancer, state scientists found that exposure to secondhand smoke raises by 50 percent to 80 percent the risk of premature birth.
Marty said scientists previously had associated passive smoking with low-birthweight babies, but the finding about premature birth is new.
The study was requested by the California Air Resources Board, which is considering whether to define environmental tobacco smoke as a toxic air contaminant.
If it does, the board known for its trend-setting regulations on motor vehicles could extend its reach to cigarette fumes.
At Philip Morris USA in Richmond, Va., spokeswoman Jennifer Golisch would not discuss the study.
She said the tobacco company has not decided whether to file a comment on the report.