Low levels of BPA raise breast cancer risk in rat offspring.

Feb 16, 2009

Jenkins, S, N Raghuraman, I Eltoum, M Carpenter, J Russo and C Lamartiniere. 2009. Oral exposure to bisphenol A increases dimethylbenzanthracene- induced mammary cancer in rats. Environmental Health Perspectives doi:10.1289/ehp.11751.


For the first time, scientists have shown that low levels of bisphenol A, even below levels considered safe by the EPA, increase breast cancer risk in rats exposed through their mother’s breast milk.

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A first of its kind study shows that low dose exposure to bisphenol A (BPA) during lactation increases the chance of breast cancer in rats.

Early developmental exposures can have long lasting and adverse health effects. This is the first study to show that a mother rat’s exposure to BPA during lactation increases her daughter’s chances of breast tumors.

Rats were used in this study because of the similarity in mammary (breast) gland development with that of humans.

If this study could be extended to humans, it suggests that current safety standards fail to adequately protect the public. Current standards -- which are being reevaluated -- do not take into account recent findings that pertain to health effects from very low level exposures of BPA and related endocrine disruptors.

Bisphenol A, or BPA, is a widely-used compound found in polycarbonate plastics and resins that line food and drink containers. Plastic baby bottles, teething toys and cans that contain formula can have BPA.

At least 95 percent of adults -- and at least that many children -- had detectable levels of BPA in their urine, according to monitoring studies.

BPA is a known endocrine disruptor. The chemical can interfere with processes that are normally controlled by hormones, such as estrogen and testosterone.

Although considered harmless for a very long time, recent research findings challenge this assumption. One sticky point pertains to the amount of BPA necessary to cause harm.

A large number of animal studies consistently find that extremely minute amounts of BPA can adversely affect the reproductive and nervous systems. This is particularly evident if the exposures occur in the very young that are actively developing.

In this study, mother rats were fed BPA so their nursing young would be exposed through their breast milk. The concentrations of BPA used -- 25 and 250 micrograms BPA per kilogram of body weight/day -- are similar to that of estimated BPA exposure of preschool children.

The lower dose is less than the US Environmental Protection Agency's "safe" reference dose of 50 micrograms BPA per kilogram/body weight.

As adults, the offspring were exposed to another chemical that spontaneously induces mammary tumors. The authors then evaluated tumor development in breast tissue of the daughters.

The rats that were exposed to BPA through their mother’s breast milk developed more mammary tumors more rapidly than the nonexposed rats.