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 a new study published in Environmental Health Perspectives.
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.
Studies have linked exposure to estradiol and related estrogens with an increased risk of breast cancer, as well as reproductive problems. As a result, the use of parabens in consumer products increasingly has become a public health concern. How much parabens might contribute to breast cancer risk is unclear.
Existing chemical safety tests, which measure the effects of chemicals on human cells, look only at parabens in isolation and fail to take into account that parabens could interact with other types of signaling molecules in the cells to increase breast cancer risk.
The researchers activated the HER2 receptors in breast cancer cells with a growth factor called heregulin that is naturally made in breast cells, while exposing the cells to parabens. Not only did the parabens trigger the estrogen receptors by turning on genes that caused the cells to proliferate, the effect was significant: The parabens in the HER2-activated cells were able to stimulate breast cancer cell growth at concentrations 100 times lower than in cells that were deprived of heregulin.
The study demonstrates that parabens may be more potent at lower doses than previous studies have suggested, which may spur scientists and regulators to rethink the potential impacts of parabens on the development of breast cancer, particularly on HER2 and estrogen receptor positive breast cells.