We’ve known for quite some time that BPA (bisphenol A) is an endocrine disruptor. We’ve known since at least 2002 that BPA may change behavior in female rodents making them less attentive mothers. Exposed mothers spend less time with their offspring, and may be less likely to retrieve them back to the nest if they stray. Or are displaced by a researcher. That is one of the ways by which researchers test rodent parenting skills. In many rodent species, only the female is involved in parental care. But others are more like us, where both partners are involved in caring for offspring. A new study (2015) shows that male behavior may also be altered by BPA. Investigators used a species of mouse where both parents are involved in infant care. The newer study with males is important because because only female behavior had been studied before.
How can a chemical like BPA change behavior?
Chemicals that happen to resemble the normal molecules that control development can change the way the brain develops. BPA resembles estrogen. It resembles estrogen enough that it can interact with estrogen receptors or block them. There are different kinds of estrogen receptors. BPA can either block them or activate them depending on what kind of receptor it hits. This is particularly important during fetal development because any abnormalities that develop are likely to persist. An adult with the occasional too much estrogen here or there will probably be fine. I explained this to my ex once, but he continued to recoil from BPA in sales receipts like a teenage girl offered a spider. An adult human male is at much less risk than an infant, but, to be fair, no one has tested them yet. Teenagers, it should be noted, may be more vulnerable to estrogen-like chemicals (such as BPA) than adults (see Blaustein et al. 2015) because their brains are undergoing so many changes.
Estrogen is important in brain development and influences later typical male and female behavior. BPA-exposed males were less likely to mark their territories when another male was around. Researchers suggest this is important because they may be less likely to engage in other male-mouse behaviors like protecting their mates from other males that could reduce their reproductive success. While BPA does seem to influence how males dosed with BPA during development behave as adults, the effects are stronger in females. BPA appeared to influence how males were “viewed” by females. Females seemed to be less invested in the care of infants produced by BPA-dosed males. Why is unknown. Did BPA make the fathers dorkier? Was their less masculine behavior enough to make the mother mice value their own offspring less? Did males exposed to BPA produce offspring less able to evoke nurturing behavior in their mothers? There have been a few headlines “BPA turns Parents into Deadbeats” etc. That is a bit of a jump, but interesting to think about in terms of what studies might be designed to evaluate humans: “BPA-exposed men express less interest in football” or “BPA-exposed men are more likely to share the remote during couple-based TV activities.”
What makes a woman a good mother anyway? What makes her value her mate? Surely a lot of social factors are involved, but there are complex hormonal and neurological factors that are likely important as well. The two are probably intertwined. Too much to discuss here. What is important is that there is so much we do not understand about ourselves and and so much we don’t understand about what determines who we become. Why add BPA to the mix?
Conclusion for BPA
Early exposure to BPA may alter behavior in adulthood. We don’t know enough about BPA or about development to know if the levels at which people are exposed are completely without impact. Until we know more, be conservative, especially if you are pregnant or might become pregnant. Use a glass bottle or a non-plastic cup. Plastic is bad for the environment anyway.
Blaustein JD, Ismail N, & Holder MK (2015). Review: Puberty as a time of remodeling the adult response to ovarian hormones. The Journal of steroid biochemistry and molecular biology PMID: 26004504
Palanza PL, Howdeshell KL, Parmigiani S, & vom Saal FS (2002). Exposure to a low dose of bisphenol A during fetal life or in adulthood alters maternal behavior in mice. Environmental health perspectives, 110 Suppl 3, 415-22 PMID: 12060838
Williams SA, Jasarevic E, Vandas GM, Warzak DA, Geary DC, Ellersieck MR, Roberts RM, & Rosenfeld CS (2013). Effects of developmental bisphenol A exposure on reproductive-related behaviors in California mice (Peromyscus californicus): a monogamous animal model. PloS one, 8 (2) PMID: 23405200
Rosenfeld CS (2015). Bisphenol A and phthalate endocrine disruption of parental and social behaviors. Frontiers in neuroscience, 9 PMID: 25784850