Women who are exposed to smoke are at three times higher risk for breast cancer than non-smoking women not exposed to passive smoking, according to a new study.
"Everyone should avoid secondhand smoke," said Lizbeth Lopez-Carrillo, professor of epidemiology, at the National Institute for Public Health, Mexico City, Mexico.
"Tobacco smoking produces both mainstream smoke, which is drawn through the tobacco column and exits through the mouthpiece during puffing, and environmental, side-stream smoke, which is emitted from the smoldering tobacco between puffs," she said.
Lopez-Carrillo and colleagues examined 504 women with confirmed breast cancer and compared them with 504 healthy women of similar age.
Compared with women who had never smoked and had no passive smoking exposure, women with passive smoking exposure had a threefold higher risk for breast cancer.
Among women who actively smoked, the researchers found an increased breast cancer risk; however, this association was only significant if women began smoking between puberty and the birth of their first child.
"Active and passive smoke exposure is a modifiable risk factor for breast cancer. Reducing not only active smoking, but also passive smoking, will prevent new breast cancer cases in this population," said Lopez-Carrillo.