A new study has reported that prenatal exposure to low levels of bisphenol A results in precancerous changes in the mammary glands of female offspring in a mouse model of breast cancer. Bisphenol A is one of the highest-volume chemicals produced worldwide; it can be detected in the body fluids of over 90% of the human population. Originally created as an estrogenic compound, it is now used to manufacture food and beverage containers, thereby resulting in uptake with food and drinks. There is concern that even low-dose exposure to bisphenol A could have developmental effects on hormone-responsive organs, including the breast.

In the study, the authors sought to answer the question as to whether perinatal exposure to a range of low doses of bisphenol A is sufficient to alter breast tissue hormone response later in life, with a possible impact on risk of breast cancer. The authors used a mouse model to mimic human exposure, adding bisphenol A to the drinking water of mouse breeding pairs.

The mammary glands of the female offspring of these pairs were analyzed at puberty. The analysis demonstrated that estrogen-dependent transcriptional events were modified and the number of terminal end buds (estrogen-induced proliferative structures which are considered to be targets of malignant transformation) was increased in a dose-dependent manner. In fact, adult female offspring had an increase in mammary cell numbers comparable to that seen in females exposed to diethylbestrol (DES). DES exposure has been linked to increased breast cancer risk. In addition, two key mediators of hormone function that have been implicated in the control of mammary stem cell proliferation and carcinogenesis were shown to have increased induction by progesterone in the mammary glands of bisphenol A-exposed mice. The authors conclude that perinatal exposure to environmentally relevant doses of bisphenol A alters long-term hormone response that may increase the propensity to develop breast cancer.

Comments regarding the study

Bisphenol A, phthalates, and styrene can leach into food when certain plastics are heated, microwaved, put under pressure or simply scuffed and worn. Plastics that may leach these substances include (1) polyvinyl chloride (PVC), which may be found in cling wrap, some plastic squeeze bottles, and cooking oil bottles; (2) polystyrene, which may be found in styrofoam food containers and disposable cups and bowls; and (3) polycarbonates, which may be found in plastic baby bottles, water bottles, and clear plastic sippy cups (bisphenol A is used in making polycarbonates). Children and adults alike should avoid all but temporary, low temperature uses of these products. Plastic containers may be marked with a number in a triangle-like icon. Plastics marked 1, 2, 4 or 5 use less toxic additives in their manufacture. Products that use polyvinyl chloride should be marked with 3, polystyrene with a 6, and polycarbonate with a 7 these are the ones to avoid.

Please see our article on how to protect our daughters from breast cancer for more information.