Tom Spears, Canwest News Service
It has been a busy winter for bisphenol A, a component in some plastics that kept a low profile for 60 years, until studies began suggesting it may be harming people by leaking out of plastic containers. Harming babies and fetuses especially.
The chemical, widely known as BPA, is common in the epoxy resin that lines metal food and drink cans. It is also found in plastic food containers, some brands of baby bottles, and the large reusable water bottles favoured by athletes and hikers.
BPA is the main ingredient in polycarbonate, a tough, flexible plastic that resists food odours and stains.
But it’s under attack from many directions, following suggestions that it makes lab rats prone to prostate and breast cancer, diabetes and obesity. Industries that use polycarbonate – and some government health agencies – insist the material is safe.
Bisphenol A is present in most of our bodies, having “migrated” from soup and soft drink cans or water bottles. In tiny amounts, BPA acts like a female sex hormone. In the first major study of the chemical in 2003-04, the U.S. Centers for Disease Control and Prevention found it in 93% of Americans. It’s not yet known whether the level is rising or falling.
It is found at the highest levels in children (including teenagers) and fetuses; some animal studies suggest it can prevent organs from forming properly.
All at once:
– Health Canada is studying BPA as one of 200 chemicals “of interest to Canadians” where there’s some evidence of toxicity. It expects to report in May on how much of the chemical leaches out of polycarbonate baby bottles and infant formula cans.
– The U.S. National Toxicology Program is reviewing possible human health effects of BPA exposure from polycarbonate containers. It’s due to report this summer.
– A U.S. congressional committee sent letters to baby formula manufacturers, including Nestlé and Mead Johnson, asking if they use BPA in packaging and test for it in infant food.
The committee is also asking if the Food and Drug Administration was wrong to conclude the chemical is safe for such uses.
– After a parents’ rally on Queen’s Park, Premier Dalton McGuinty said Ontario could become the first jurisdiction in Canada to place restrictions on bisphenol A.
– Mountain Equipment Co-op removed polycarbonate plastic Nalgene bottles from its stores last year. Lululemon did the same. Both companies said the decision was a precautionary measure. MEC still sells Nalgene brand bottles and food containers made of other plastics.
– Two weeks ago, a University of Cincinnati study found that running boiling water into a polycarbonate container – regardless of its age – made BPA leach out up to 55 times faster. Microwaving the plastic has a similar effect, said the published study by scientist Scott Belcher.
– And on Thursday, an activist group called Environmental Defence reported on lab tests it commissioned, which found that BPA leaches out of polycarbonate baby bottles made by Gerber, Playtex and Avent.
This year, the world will use between 1.5 billion and 2.8 billion kilograms of BPA.
Now, prompted by a flurry of studies on rats, scientists are wondering: What if it’s dangerous?
In order to answer this question, they must first answer another: What’s the proper way to poison a rat? More precisely, how does feeding a rat industrial chemicals for a few weeks accurately forecast the health effects on humans who get much smaller doses spread over a lifetime?
The BPA story began 60 years ago, and its origins had nothing to do with plastic.
In the 1940s, scientists trying to reduce the number of miscarriages wondered if a synthetic estrogen drug would help women carry fetuses safely to term.
They settled on a chemical called diethylstilbestrol, better known today as DES. It did unexpected but horrible damage; the women who took it were mostly unharmed, but their children suffered health problems, particularly reproductive tract cancers at a very young age in “DES daughters.”
But while drug companies experimented with DES, they were also testing an alternative called bisphenol A, or BPA for short. It was a chemical first discovered in 1891 by a chemist who had no use for it at the time. Like DES, it is a synthetic version of estrogen, the group of hormones that regulate most of the female reproductive system. But it didn’t perform as well in drug tests: BPA didn’t dissolve easily in water or stay in the body for long. Unlike DES, it needed to be injected to work.
Bisphenol A was discarded as a drug for pregnant women, but in 1952 the plastics industry found another use. It worked really, really well as a plastic.
In hardened form, it’s called polycarbonate and forms a clear, durable plastic (which can also be coloured). We see it every day in CDs, in automotive parts, in the resin lining applied to the insides of food and soft drink cans, in toys.
For years, athletes and hikers have used colourful BPA bottles for water. They’re strong; they can hold boiling liquids; they don’t crack in cold weather or in hot dishwashers. Environmentalists like them, too: They’re reusable for many years.
Baby formula bottles are often (not always) made of BPA, too. The material doesn’t shatter, and parents find them easy to heat in the microwave.
The debate about BPA is much like disputes over other environmental chemicals, from dioxin to manure from factory farms. Force-feed the stuff to rats and they get sick. But what about humans in the real world? There’s no way to say.
When testing drugs, scientists give real drugs to one group and a placebo to another. Afterward, they compare their health.
But they can’t do this with pollutants, obviously, since they could poison people. So instead they test rats. Today there are well more than 100 studies on the effects of BPA on rats, all stemming from the fact that early research found rats injected with the chemical were more prone to obesity, cancer and insulin resistance.
Among existing studies, however, there is a nasty split, all based on how each scientist chose to give BPA to the rats.
Last spring, a trade journal of the American Chemical Society, called Chemical and Engineering News, surveyed the studies published to date. Its finding: “There is growing concern that the chemical may cause similar adverse effects in humans, particularly in babies and young children. But there are vast discrepancies in the findings of government-funded and industry experiments that have explored the health effects of BPA.”
“Among government-funded experiments on lab animals and tissues, 153 found adverse effects and 14 did not,” wrote senior editor Bette Hileman. In contrast, “the majority of those that reported no harm were funded by chemical corporations.”
The defects, in studies that found them, included a tendency to develop diabetes and obesity, enlarged prostate, changes in the breast tissue that suggest being prone to breast cancer, and a cluster of slight deformities in the male reproductive tract that scientists call “feminization.” These deformities are seen to occur in animals exposed to so-called endocrine disruptors, or environmental chemicals that mimic hormones such as estrogen and may upset the normal development of reproductive systems.
Ms. Hileman’s survey reported “a number of potential sources of bias behind these inconsistent study outcomes, including the use of strains of rats that are insensitive to estrogen and choosing batches of animal feed that vary widely in their estrogenic activities.”
In other words, Ms. Hileman charges that some experiments were designed to keep the rats healthy to demonstrate that the chemical is harmless in small amounts.
The U.S. National Institute of Environmental Health Sciences decided to sort out the confusion. It is now reviewing and hopes by next summer or fall to release public information on whether there’s health danger, and if so, how much.
Its early draft reveals only mild worry. There is “some concern” that exposure to BPA in the womb causes neural and behavioural changes, but only “minimal” or “negligible” concern about other possible health damage.
But already, the panel conducting the review is under attack from the anti-BPA side made up of academic researchers such as Frederick vom Saal at the University of Missouri-Columbia, and Scott Belcher (University of Cincinnati). That’s because it discarded many studies that indicated danger from the chemical, but accepted most of the industry-sponsored studies that showed no potential for harm.
They explained that the studies that found BPA harmful used the wrong method to deliver the chemical to lab rats. (Industry studies generally fed BPA to the rats by mouth.) Injecting the chemical into the rat’s blood does not mimic the type of exposure that people have. We don’t inject BPA, noted the panel of government reviewers, we swallow little bits of it as molecules detach from the plastic in food and drink containers.
The “pathway” of exposure makes a difference. When we eat it, our metabolism breaks down and excretes a lot of it. That doesn’t happen as readily if the chemical is shot directly into the bloodstream.
Last month, anti-BPA forces launched a counter-attack. They published a new study in a science journal called Reproductive Toxicity, showing that rat fetuses and babies process the chemical in a different way than adult rats do.
The University of Missouri study gave high and low doses of BPA to three-day-old female mice. Half got the chemical by mouth and half by injection. Afterward, the mice with injections had the same blood levels as the mice with oral doses.
“It shows that for the baby animals, it doesn’t matter whether they get the dose orally or they get the dose through the blood,” Hileman explains. “They can’t really metabolize it the way adults can. So they seemed to be harmed (equally) by injection and by oral exposures.”
The implication: “If you’re pregnant, then it might be much more harmful to your baby and might not even bother you. The liver (in the fetus and baby) doesn’t break it down. If you’re in the womb, you’re not eating and your system is different. Even in the first year (after birth), your system is not the same as an adult’s. So if you’re getting it in your formula or your breast milk, it might be more harmful to you than it would be to your mother or father.
“The only thing you can look at is that exposures to the animals at extremely low levels now seem to cause harm, to those animals.
“We can’t do those experiments on us, but we do know, (or) have a good idea, how much babies are exposed to in the womb. And that’s as much as the animals that get harmed” in the lab.
The National Toxicology Program’s panel released a letter after this news became public, promising to consider all views about different methods of exposure in making its decision.
When MEC pulled polycarbamate water bottles and food containers, Nalgene responded that it, like government agencies, still feels the material is safe. It adds, “several scientific panels including the European Union’s Scientific Committee on Food, the National Toxicology Program and the Harvard Center for Risk Analysis have concluded that the weight of scientific evidence does not support the hypothesis that low doses of BPA adversely affects human health. None of the large studies conducted has substantiated the claims made by those performing some of the smaller studies frequently cited.”
“They (BPA-based plastics) have been used in the industry for over 60 years,” said Gail Wood, spokeswoman for Mead Johnson Nutritionals, a baby formula manufacturer and a division of Bristol-Myers Squibb Company. “They’re very important because they are the absolute best in keeping product fresh and keeping contaminants out of whatever food product is canned . . . using those liners.
“It has been proven time and time again by leading government testing authorities to be safe. So it’s sort of like: Don’t fix it if it’s not broken.
“It is a very important resin for the industry. If there were something better . . .
“We trust that industry and all the governments of Japan, Europe and the U.S. to be on the lookout for enhancements and betterment. But to date there hasn’t been any,” she said.
“There are substitutes (other epoxies), but know this, too: Every alternative has its inherent risks and benefits. So because the risks are so low in epoxy resins, and their efficacy is so high, they are by far the best possible packaging component to use for a myriad of applications.”
Why not use unlined metal?
“Oh, my gosh! There is a significant leaching problem with those metals and alloys,” Ms. Wood said. Traces of nickel, aluminum or other toxic metals could leach out of the can, contaminating the food.
Resin linings also seal out bacteria, moisture and oxygen (which spoil food).
“I wish people who were scaring consumers would present more of a balanced story.”
The BPA-based resins are also flexible, so the lining stays intact if something dents the can.
“The key take-away (message) is that there probably are alternatives – not as good – and every alternative is going to have its inherent risks and benefits.”
The North American Metal Packaging Alliance, representing steel and aluminum can makers, says BPA-based epoxy is “unsurpassed” in staying intact through the high sterilizing temperatures used in food canning.
“This sterilization process guarantees that the packed food is safe from microbiological contamination (‘food poisoning’) making the canned food the safest for consumers,” it says in a statement on BPA.
In the meantime, testing a chemical that gives off only a weak hormonal signal is not simple.
“It’s very difficult because these sorts of compounds don’t work like your normal toxins,” the University of Cincinnati’s Belcher says. “Part of the difficulty is that when you talk about hormone systems, they’re very sensitive to very small changes. And often what happens – and BPA is a good case – is that it’s lower doses that have the bigger effects, which is very different for toxicology and risk assessment the way we do it.”
The body’s hormone receptors ignore a big dose, because hormones don’t arrive in big doses. But if they see a small dose, they say: That’s a hormonal signal.
In the continuing battle over public opinion, it’s easy to be fooled. The Toronto Star was duped last month: It published a 10-part article listing various health scares that it said were “unfounded.”
The Star was actually reprinting material written by the American Council on Science and Health. This group is paid by the U.S. chemical industry and advances its views aggressively .
Its article, reprinted as health news in the Star, told readers: “The Bottom Line: The United States Environmental Protection Agency concluded BPA is safe and set a maximum acceptable dose of 0.05 milligrams per kilogram of body weight. Only workers exposed to BPA on the job have shown any significant effects, experiencing irritation of the eyes, respiratory tract and skin. These symptoms resulted from inhaling BPA, not from ingesting it through foods and beverages.”
That’s true as far as it goes, though it doesn’t mention the continuing reviews.
On the other side, 38 BPA researchers – not industry reps – who gathered in North Carolina for a workshop last August drew up a list of known, suspected and uncertain aspects of the chemical, known now as the “Chapel Hill Consensus Statement.” It says the following statements are “likely, but require confirmation:
” . . . Exposure during sensitive periods in organogenesis (that is, when organs are forming in the fetus) may increase susceptibility to development of cancers in some organs, such as the prostate and mammary glands.
“Early life exposure to environmentally relevant BPA doses may result in persistent adverse effects in humans.
“The function of the immune system can be altered following adult exposure to BPA.”
And the exact effect on humans in the real world? They put that down as uncertain:
“There is a need for epidemiological studies relating health outcomes to BPA exposure particularly during sensitive periods in development,” they concluded.
Truth and rumours muddy plastics debate
Tom Spears, Canwest News Service