These days the baby aisle shelves are lined with products proudly announcing: “BPA-free.” As a mom and a consumer, this is reassuring. BPA (bisphenol A), a chemical used in the production of plastics and many other products, has been linked to a variety of health problems such as reproductive disorders, diabetes and cardiovascular disease. A 2003-2004 national health survey by the Centers for Disease Control and Prevention found BPA in more than 93 percent of 2,517 urine samples from people age 6 and older.
In 2008, the Food and Drug Administration stated that BPA was safe for use in food-related materials such as plastic food containers and the linings of food and beverage cans, including containers for liquid infant formula. Last year, the FDA ruled that BPA could no longer be used in the manufacturing of baby bottles and sippy cups; this action came after the chemical industry and major manufacturers had abandoned the use of BPA in those products.
But the chemical is found in many other common items: medical devices, dental sealants and compact discs, to name a few. Even paper receipts from the grocery store and ATM machines often contain BPA. In short, it’s pretty hard to avoid the chemical.
In the past few years, the FDA has expressed greater concern about BPA. In 2009, the National Institutes of Health launched a $30 million, five-year program in collaboration with the FDA and the CDC to examine long-term health outcomes associated with developmental exposure to BPA. Research from this effort will be pouring out over the next few years. But the studies already emerging continue to add to the evidence that the safety of BPA is highly uncertain.
These and many other studies have converged on a central message: Even at low levels and particularly during prenatal development and early childhood, exposure to BPA — known to mimic the hormone estrogen — can have subtle but detrimental effects.
When chemicals such as BPA mimic hormones, it leads to what’s called endocrine disruption. “The effect is not necessarily toxic in the traditional sense,” says Sarah Vogel, director of the health program at the Environmental Defense Fund and author of “Is it Safe? BPA and the Struggle to Define the Safety of Chemicals,” but it is a disruption.
Hormonal signals work the way a lock and key work. We have receptors (the locks) that receive signals from hormones (the keys). “[BPA] is almost like a little master key because it can fit into many of these little locks that are in your body and in your cells,” says Emilie Rissman, a behavioral neuroendocrinologist at the University of Virginia.
Rissman and other researchers are finding that when humans and other animals are exposed to BPA during critical developmental windows such as in the womb and in infancy, the chemical can scramble cellular signals and leave lasting biological effects.
For instance, a 2012 study found that when female rhesus monkeys were exposed to low doses of BPA during their second or third trimesters of pregnancy, the chemical caused defects in egg formation in the offspring. In other studies of the same rhesus monkeys, researchers found abnormalities in the development of other organ systems including the brain, lungs and reproductive tract following prenatal BPA exposure.
Researchers have also found that newborn rats that were exposed to low doses of BPA for a short period had a significantly higher risk of prostate cancer (an estrogen-induced cancer) later in life. “It’s as if early life exposure [to BPA] programmed a memory in the prostate gland,” says Gail Prins, a physiologist at the University of Illinois in Chicago who led that research. In soon-to-be published studies, Prins’s group has found nearly identical results with human prostates created from stem cells and exposed to BPA during development.
Prins’s work and that of others is finding that BPA is causing alterations at the level of the epigenome — the modifications, or tags, that tell genes when to turn on and off. For instance, a study published this year found that BPA disturbs the epigenetic programming of gene expression in the brains of mice.
Most concerning, recent studies suggest that these epigenetic changes may be heritable between generations. Rissman and her colleagues have found that low-level exposure to BPA in pregnant mice suppresses gene expression of two proteins that are important in regulating social behavior — oxytocin and vasopressin — and alters social behaviors in the fourth generation (the great-great grandchildren) of the exposed mice. The implications of Rissman’s work are “profoundly disturbing,” says Pete Myers, chief scientist at Environmental Health Sciences, a nonprofit research organization in Charlottesville. The levels of BPA that Rissman is experimenting with, he notes, are in the same range as those found in most people.
We can reduce our BPA exposure by making choices such as opting for electronic receipts, using fresh and frozen vegetables rather than canned, choosing glass and stainless steel containers and not microwaving food in polycarbonate plastic containers. (The heat in a microwave can cause plastic to break down, allowing BPA to leach into food or liquids.) Still, the chemical is all around us, and there is controversy around whether current replacements are any safer.