Lotion ingredient 'cancerous' even in lower doses

A new study has linked low doses of a chemical found in shampoos and cosmetic products to breast cancer.

Estrogen-mimicking chemicals called parabens, which are commonly found in an array of personal care products, may be more dangerous at lower doses than previously thought, according to the University California, Berkeley study.

The findings could have implications for the development of breast cancer and other diseases that are influenced by estrogens. The study also raises questions about current safety testing methods that may not predict the true potency of parabens and their effects on human health.

Parabens are a class of preservatives widely-used in consumer products like shampoos, cosmetics, body lotions, and sunscreens. The chemicals are considered estrogenic because they activate the same estrogen receptor as the natural hormone estradiol.

How much parabens might contribute to breast cancer risk is unclear. "Although parabens are known to mimic the growth effects of estrogens on breast cancer cells, some consider their effect too weak to cause harm, but this might not be true when parabens are combined with other agents that regulate cell growth," says lead investigator Dale Leitman.

While this study focused on parabens, it's also possible that the potency of other estrogen mimics have been underestimated by current testing approaches, says co-author Chris Vulpe.

In particular, one area of increasing concern is how exposure to multiple chemicals during critical periods of development including puberty and pregnancy increases a person's susceptibility to breast cancer later in life.

The study appears in Environmental Health Perspectives.