THURSDAY, Jan. 12, 2012 (HealthDay News) -- For several years, researchers have studied a possible link between substances called parabens -- widely used as a germ-fighting preservative in cosmetics such as deodorant/antiperspirants -- and breast cancer.
Investigators have learned that parabens, also found in some drugs and food products, can mimic weakly the action of the female hormone estrogen -- an established risk factor for breast cancer. And the fact that a disproportionate number of breast tumors occur nearer the underarm also had scientists wondering.
But now, British researchers who examined breast tissue samples from 40 women who had mastectomies have found that traces of parabens are widespread in tissues, even in the seven women who said they'd never used underarm products.
"The implication is that in these seven nonusers, the paraben measured must have come from another product or products," said Dr. Philippa Darbre, a cancer researcher at the University of Reading who has long studied the issue.
In the study, published online in January in the Journal of Applied Toxicology, Darbre and her colleagues report that one or more kinds of parabens were found in 158 of the 160 samples taken from the tissue collected from the 40 women. They found 96 samples contained all five of the most common paraben esters (forms).
The levels of paraben found were higher, by about four times, than Darbre found when she did a similar but smaller study in 2004. "Since 2004, many manufacturers (although not all) have been removing parabens from the underarm deodorant/antiperspirant products and so I was rather surprised when we found higher levels of parabens in these breast tissues (sourced after 2004)," Darbre said.
Higher levels of one form of paraben were found in the region of the breast closest to the armpit, she said, and the women had a disproportionate incidence of breast cancer in that area.
However, Darbre cautioned that the research cannot be taken to imply cause and effect.
"Although estrogen is an acknowledged component in the development of breast cancer, it remains to be established as to whether environmental chemicals with estrogenic [estrogen-like] properties contribute a functional component to the disease process," she said.
"I remain as ambivalent as ever about hounding any one chemical," she added. "I feel sure the issue is bigger than one chemical." Darbre believes the parabens found in breast tissue come from a wider range of products than underarm cosmetic products.
More research is needed, Darbre noted. Meanwhile, she suggests women cut down or cut out the use of cosmetic products as much as possible. "We simply use too much in the modern world -- too much for our body systems and too much for the wider environment," she said.
For its part, the American Cancer Society finds no clear link between deodorant/antiperspirants and breast cancer. In a posting on its Web page, it notes that, "There are no strong epidemiological studies in the medical literature that link breast cancer risk and antiperspirant use, and very little scientific evidence to support this claim."
Dr. Michael J. Thun, vice president emeritus of epidemiology and surveillance research for the American Cancer Society, reviewed the new study findings. The fact that the preservatives were found in the majority of the breast tissue samples cannot be taken to imply they actually caused the breast cancer, he said, reiterating a point the authors also emphasized.
"Rather," Thun said, "the study merely confirms earlier, smaller studies which detected parabens in breast tissue of women with cancer. It shows that parabens can be absorbed (probably from personal care products) and the underarm deodorant is not the only source."
Other studies have found that parabens, also found in lotions, makeup and sunscreen products, can be absorbed through the skin, according to the American Cancer Society. However, the society says more and larger studies are needed to find out what effect, if any, the parabens might have on breast cancer risk.
To learn more, visit the American Cancer Society .