A survey of Massachusetts women has found a potential link between the use of household cleaners and air fresheners and breast cancer.
The study included interviews with 787 women who had breast cancer and 721 who did not. Researchers asked all the women about pesticide use but found little association.
But when about 400 women in each group were asked about cleaning products, researchers found a potential connection.
In fact, breast-cancer risk was highest among women who reported the most use of cleaning products and air fresheners; it was double the risk for those who reported low use of the products. Most study participants were white and middle-aged and were part of the Cape Cod Breast Cancer and Environment Study, which had financial support from the state of Massachusetts.
The results are published in the journal Environmental Health.
The connection was drawn mostly between mold and mildew cleaners and air fresheners. Surface and oven cleaners were not associated with increased risk. Chemicals of concern include synthetic musks, phthalates, 1,4-dichlorobenzene, terpenes, benzene and styrene and some antimicrobial agents, said Julia Brody, the lead researcher and executive director of the Silent Spring Institute.
Studies of this nature come with an inherent weakness, called recall bias. The researchers acknowledged that women who have cancer and believe in an association with cleaners might be more likely to report high use of them.
That said, the study adds weight to previous animal research showing that the same chemicals cause mammary-gland cancer in animals and disrupt the endocrine system, contributing to tumor growth, Brody said.
Much about the causes of breast cancer remains unknown. Many patients believe in environmental links, but they are notoriously difficult to prove.
"Although there seems to be an association between cleaning products and cancer, that's a long way from saying, 'Cleaning products cause breast cancer,'" said Dr. Charles Shapiro, director of breast medical oncology at the Ohio State University Comprehensive Cancer Center.
"I wouldn't take too much from it," Shapiro said, noting that the study was relatively small and that it's impossible to draw definitive conclusions about cause and effect. He also cautioned that what is found in the laboratory in animal models doesn't necessarily play out among humans.
"The take-home, if any, is if you're worried about it, try to avoid those products," he said.
Sandra Steingraber, a New York ecologist, cancer survivor and author of Living Downstream, said she'd advise everyone to stop using chemical cleaners. She uses vinegar and baking soda to clean her house.
"I just see this as such an easy problem compared to a lot of things," said Steingraber, who is on the faculty at Ithaca College.
The new research, she said, "points to the really vexing problems of trying to make correlations between past exposures and present disease rates."
Steingraber said: "Clearly, the conversation is shifting now. We can't just sort of look at the murky evidence on cancer and the environment and sort of set it aside because it's too inscrutable."