This time last year, most of us had never heard of bisphenol A (BPA), but by spring it had become public enemy number one of environmental hazards. In April, Health Canada declared that BPA was “toxic to human health” and Minister of Health Tony Clement announced that polycarbonate baby bottles, which contain BPA, would be banned.
But even before then, retailers had been pulling polycarbonate baby and water bottles off shelves. Parents had been searching stores and the Internet for glass bottles and other BPA-free baby bottles, and trying to figure out if they should discard sippy cups, Tupperware containers and even plastic lunch boxes. All of this was reported with high drama, fuelled by media.
Actually, Health Canada’s scientific report makes BPA seem less scary than other chemicals like the PCBs, dioxins and pesticides we’ve been hearing about for years. A Health Canada fact sheet states that “bisphenol A does not pose a risk to the general population.”
So why the big fuss? Three reasons. One is that BPA is remarkably omnipresent in our lives, so if it is causing harm to humans or the environment, we’d best find out. Second, teeny amounts have been detected in various human fluids and tissues. We don’t know how long it hangs around or whether it’s connected to any diseases in humans. Finally, and perhaps most important, compared to other environmental chemicals, BPA is relatively unregulated and unscrutinized. Less than 10 years ago, the prevailing view was that BPA was not an environmental threat. That, as we have seen, is beginning to change.
In pure form, bisphenol A is a white crystalline powder that looks something like table salt. Invented over a hundred years ago, BPA came into widespread use in the 1950s when scientists discovered it could be used to make a high-test plastic called polycarbonate. Like glass, polycarbonate is see-through, but it’s much lighter and almost shatterproof.
BPA became a foundational ingredient in products found in all Canadian homes: food containers, eyeglasses, sports and bicycle helmets, computer housings, CDs and DVDs, some water bottles, sippy cups and baby bottles. It is also used to make the epoxy resin linings that make food cans resistant to corrosion, thus increasing the shelf life of canned foods, including infant formula.
So, we’re talking about a pretty handy and ubiquitous chemical, which just happens to be an endocrine disruptor: a chemical that can act like a hormone or interfere with hormonal activity in the body, says Laura Vandenberg, a developmental biologist and research associate at Harvard Medical School. “Specifically BPA is an artificial estrogen, one of many we are exposed to. Others include certain chemicals used in some insecticides, detergents, household cleaners and sunscreens, as well as plant estrogens found in food — soy products, for example,” says Vandenberg.
“The human organism wasn’t meant to be exposed to chronic amounts of synthetic estrogens, particularly during fetal development and babyhood,” explains Vandenberg. “Artificial estrogens have been shown to cause changes in animals, early in life, which can contribute to the development of reproductive problems such as low sperm count and reproductive cancers like breast, uterus and prostate in adulthood.”
How does BPA compare to other environmental toxins?
Unlike PCBs and other persistent organic pollutants, BPA breaks down quickly. Even so, while it’s around, it can cause harm to wildlife. In fact, one of the strongest statements in the Health Canada report, was that it’s “acutely toxic to aquatic organisms.”
BPA does not build up in the human body the way many other pollutants do. Most of it passes through adult bodies within hours. Gary Ginsberg, a Connecticut-based toxicologist specializing in risks to children and author of What’s Toxic, What’s Not, says, “The potential risks to infants would be greater, however, because they are likely to clear BPA more slowly than adults.”
No studies have definitely documented harm to humans that can be attributed to BPA alone. And the problems possibly attributable to BPA could be caused by other factors, in some cases other artificial estrogens, according to Vandenberg. “One of the problems with assessing the damage done by BPA is that human beings are exposed to so many different man-made estrogens, anti-estrogens and other endocrine disruptors,” she says. “However, I’m concerned because the levels of exposure estimated for humans are analogous to the levels shown to cause effects in mice and rats and that is the usual threshold for concern in the science of risk.”
As with many chemicals, the biggest concern may prove to be BPA’s effects on the developing fetus. It has been detected in amniotic fluid and placental tissue. Ottawa family physician Kapil Khatter, a consultant with Environmental Defence, the Toronto-based advocacy group which has led the charge against BPA, comments, “We have focused on bottles, formula and food cans, but exposure to pregnant women may prove to be the bigger issue.”
How much BPA is getting into us?
Humans have been exposed to BPA for more than 50 years in increasing amounts. If you’re wondering whether it’s in your kids’ bodies, assume yes. The Atlanta-based US Centers for Disease Control tested 2,517 people aged seven and older and found that 93 percent had detectable levels of BPA.
There’s no data on babies and toddlers, but most estimates, including Health Canada’s assessment of scientific evidence, say that the younger you are, the more BPA you’re exposed to, especially if you are a baby fed on concentrated or ready-to-eat liquid formula.
Very important point here: Health Canada’s estimates for formula-fed babies are all based on canned concentrated liquid formula mixed with room temperature water. Less is known about powdered formula because it has not been tested as extensively, but the US-based Environmental Working Group believes, for a number of reasons, that it would contain only one-eighth as much BPA as liquid concentrate.
How are we getting it?
A careful reading of Health Canada’s report suggests that panic about polycarbonate bottles may be misplaced. The fact that got little attention in last spring’s BPA media frenzy is that 90 percent of our exposure to BPA is thought to come from eating canned food.
In fact, less than 10 percent comes from polycarbonate bottles — as long as you don’t leave boiling water in them for prolonged periods.
Health Canada estimates a formula-fed baby’s exposure would quadruple if boiling water were put into the bottle, left there to cool and then (that same water) is used to make the formula.
Still, phasing out polycarbonate bottles makes some sense. Alternatives exist and, once they flood the marketplace, as they surely will, making the switch won’t be that hard.
But if the government really wanted to reduce human exposure to BPA, they’d set targets for getting it out of the linings of food cans. Japan did this 10 years ago, switching to a polyester compound (though it still contains a bit of BPA). However, at this point, Health Canada says exposure from canned food “is not a concern for most Canadians.” Minister of Health Tony Clement has said only that government will “work with industry to reduce the use of BPA in cans containing infant formula.”
The thing about BPA...
Here’s where we get to the nub of the discussion. Although you will hear much talk of “safe levels” in the BPA debate, the cardinal toxicology rule, the larger the dose, the worse the damage, may not exactly apply. Fred vom Saal, a biology professor at the University of Missouri, says that with hormones, effects are caused by small amounts rather than large amounts. “All hormones have their normal working levels; with estrogens, amounts as low as one part per trillion can stimulate a cell — and once you get above the working level, the effect may shut off, but offer effects may occur.”
So the question is, do the minute levels of BPA that we don’t pee out hang around long enough to eventually cause harm?
That we can’t answer. A 2002 report by the World Health Organization described the science of low-dose effects of endocrine disruptors (including synthetic estrogens) as “highly controversial” with no firm evidence of human effects.
Further, in the world of front-page environmental chemicals, BPA is the new kid on the block. One reason environmentalists and some scientists pushed so hard on the BPA file this past winter is that they saw a chance to get it added to the list of chemicals slated for regulation and further study. “We’ve restricted and, in a few cases, banned a number of synthetic estrogens,” says Ginsberg. “But bisphenol A is a significant source of synthetic estrogen that has not yet been controlled.”
In sum, based on what we know right now, BPA does not appear to be the most dangerous chemical of the many we are exposed to. It doesn’t make sense to panic, but it does make sense to reduce exposure, particularly when the change itself isn’t risky. Don’t, for example, switch a six-month-old baby to cow’s milk to avoid BPA in formula or breastmilk.
It’s clear that BPA needs more study and should be more regulated because the possibility of harm to humans cannot be ruled out. But if BPA does prove to be a big concern, a ban on polycarbonate baby bottles addresses a small portion of the problem.
How do I know if it’s got BPA in it?
Usually it will be hard, see-through plastic with a number 7 on the bottom and the letters PC beside the recycling symbol. In other words, non-see-through and soft plastics, such as yogurt containers and soft-drink or water bottles, do not contain BPA.
Other plastics contain chemicals, some of which we know little about. Many soft, flexible plastics (and products including vinyl flooring) contain phthalates, a class of chemical that leaches out of products more easily than BPA and about which there is more direct evidence of human health risks.
Health Canada's estimated average daily BPA intake at various ages
Age mcg/kg* 1 month, formula-fed 0.50 1 month, breastfed 0.29 8–12 months, formula-fed 0.25 1–4 years 0.27 5–11 years 0.17 Adults 0.08 *in micrograms (millionths of a gram) per kilogram of body weight