A plastic additive has attracted activist wrath. But science says it is safe
The US Food and Drug Administration’s recent decision not to reverse the policy of the Bush administration and ban bisphenol A (BPA) came as a huge shock for environmental activists campaigning for a change in government policy.
You may never have heard of BPA but it is one of the most ubiquitous chemicals in the world. When added to plastic it makes it stronger – hard enough to replace steel and transparent enough to replace glass. It can withstand high heat and has high electrical resistance. It can be found in electronics, DVDs, the dashboards of cars, dental applications, even Tupperware. It is the key ingredient in epoxy resins and the plastic coating used to line food tins.
Pressure mounts
For months there were sensational stories designed to embarrass the FDA into abandoning its 2008 finding that the chemical is not dangerous.
My favourite headline was “BPA Wrecks Sex, Fouls Food – And Probably Worse” atop a Huffington Post piece last November written by the Environmental Working Group.
The Milwaukee Sentinel has run no fewer than 50 reports, and won a bushel of awards, excoriating the government for not restricting BPA’s use. And last December, Consumer Reports weighed in, linking BPA to “reproductive abnormalities, heightened risk of breast and prostate cancers, diabetes and heart disease”, echoing concerns that microscopic particles of the chemical could migrate from sippy-cups into babies’ milk or juice.
It all sounds frightening. And considering the Bush administration’s history of manipulating science data to support its political agenda on everything from climate research to over-the-counter contraceptives, it’s right to take concerns about potential environmental hazards seriously.
That’s why campaigners were so taken aback when the FDA refused to issue a ban, declaring that BPA posed “negligible” or “minimal” concern for most adults. Under heavy political pressure to do something to placate the campaigners, the FDA expressed “some” concern for developing foetuses, infants and children.
But when asked directly if they faced any real health dangers, the FDA minced no words. “If we thought it was unsafe, we would be taking strong regulatory action,” says Dr Joshua Sharfstein, the principal deputy commissioner of the agency.
If the FDA had taken stronger action, it would have come as a shock to regulators in the rest of the world. In the past few years, BPA has undergone comprehensive reviews and has been certified as safe in at least 10 industrialised countries. Most critically, it was declared safe by the European Union in 2006, which is striking because the EU evaluates chemicals using the “precautionary principle” – the controversial notion that environmental policy should be based on the suspected risk of causing harm rather than proof that a substance actually causes harm.
Either there is a massive conspiracy by health and safety officials around the world to cover up the true story of “killer BPA” or maybe, just maybe, there is a backstory here.
The ‘novel’ hypothesis
For years, ban proponents have challenged established scientific thinking about what dose levels of toxic substances are likely to affect humans. It is called the “new paradigm”, and it grew out of a conference led by the zoologist Theo Colborn, held in Wingspread, Wisconsin, in 1991. This like-minded group of scientists and activists believed that chemicals – not just BPA – were causing harm in humans that were not picked up by traditional tests. They claimed that while many chemicals such as BPA may not harm people at high doses they might at extremely low doses.
This counter-intuitive claim became known as the “low dose hypothesis”. This novel notion has been embraced and even promoted by public health campaigners the Environmental Working Group, and many activists and some journalists who ascribe to the “precautionary principle”. But most scientists and regulators remain dubious. According to the FDA report, “studies employing standardised toxicity tests used globally for regulatory decision making thus far have supported the safety of current low levels of human exposure to BPA”.
The FDA acknowledged, limply, that this “novel” idea does “describe BPA effects” in “laboratory animals”, but said the devil is in the details, and the novel experiments are rife with problems. Again and again, classic tests used by scientists show no harm at normal usage levels. Only a fraction of studies on BPA indicate toxic or hormonal effects, but at levels at least 500,000 times higher than humans consume. Most tests have been on rats.
Animal tests are considered an important first step in evaluating a chemical but by themselves are of “limited usefulness to human health”, as noted by the British Medical Journal recently. This is because of significant differences in biochemistry and immune systems, and so on.
Many initial animal tests by scientists embracing the low-dose notion that showed some potential harm have not been replicated when classic testing protocol was used. Even more problematically, the novel low-dose hypothesis is based almost entirely on administering BPA to rats by injection, when more than 99% of BPA is ingested orally in humans.
That raises two issues. Regulatory agencies do not put much stock in tests in which a substance is delivered in a different way from how humans experience it.
The European Food Safety Authority, which uses the “precautionary principle” in its deliberations, along with the FDA, the National Toxicology Program, Health Canada and, in fact, every national authority that has systematically looked at BPA, either rejects studies of injected BPA outright or gives primacy to oral studies.
Second – and perhaps this is the arrow to the heart of the ban proponents’ argument – when BPA is ingested orally, as is almost always the real-world case, it rapidly detoxifies, first in the gastrointestinal tract and then in the liver. Enzymes add a sugar molecule. That transforms it into a water-soluble substance known as BPA-glucuronide, which repeated studies have shown is innocuous, with a half-life of six hours. It’s easily excreted in urine.
In that light, a recent study trying to make hay over the fact that BPA is found in 90% of the population creates a false impression that the mere presence of it in humans is necessarily something to be worried about. This was widely circulated by ban proponents and reported without context or qualification by the media – including the New York Times.
A question of dosage
The question of whether BPA is harmful ultimately revolves around the murky issue of toxicity. As Paracelsus, the father of toxicology, observed: “All things are poison and nothing is without poison, only the dose permits something not be poisonous.” The world is awash in chemicals, natural and human-made. Many substances found in our foods are toxic, including essential vitamins and minerals, if consumed in large quantities. The important question is whether a particular substance is harmful at the level it is metabolised.
With that in mind, scientists use what is called risk-risk analysis to evaluate chemicals. They consider two key questions: at what levels could a substance cause harm and what would be the possible consequences if a useful chemical were pulled off the market?
Some chemicals are both ubiquitous and effective at what they do. BPA falls into that category. It’s been around for more than 100 years. More than 2.7m tonnes of it are produced globally each year, and the market is growing because the need for it is growing. There are no viable alternatives for many of its uses, such as to prevent bacterial contamination, such as botulism, in canned goods.
Consumer concerns, however unproven, about harm from possible leakage into children’s containers have prompted manufacturers to reformulate their infant containers, taking that issue mostly off the table. The only justification for banning BPA would be if it could be shown, using empirical science and tests on humans, that the hazards and costs outweigh its clear benefits.
Firm future
For those men reading this, who have been anxiously waiting to find out whether they face the prospect of erectile droop, as the EWG, the Los Angeles Times, and other news outlets have alleged, there is good news. The cited study focused on Chinese workers who handled the chemical in bulk, not with BPA in foods. The BPA levels these men were exposed to were 50 times higher than that experienced by the average American man. The National Toxicology Program, in 2008, reported “negligible concern” that men exposed at non-occupational capacities – in other words men who use plastic containers or consume canned foods – will experience reproductive problems.
Unable so far to prevail on the science in the US debate over BPA, campaigners are already shifting gears from the laboratory to politics. In January, Minnesota became the first US state to ban the chemical in baby bottles, basing that decision on the “precautionary principle”, citing fears of harm.
That same argument prevailed in Canada. In 2008, Health Canada firmly rejected claims that BPA was unsafe. “The current research tells us the general public need not be concerned,” Health Canada declared after reviewing hundreds of studies. “In general, most Canadians are exposed to very low levels of bisphenol A. Therefore, it does not pose a health risk.”
But the “precautionary principle” is embodied in Canadian (and EU, but not US) law, which forced Health Canada to ban BPA in baby products even without convincing scientific evidence. “Even though scientific information may be inconclusive,” it wrote, “decisions have to be made to meet society’s expectations that risks be addressed and living standards maintained.”
And so, in April 2008, Health Canada, citing the “precautionary principle”, banned BPA for use in products for infants and children. It was the first (and is still the only) restriction on BPA at a national level. Activists next set their sights on Europe, France in particular, which has even stricter precautionary standards.
But in a stunning turn of events, French health authorities rejected the opportunity to follow in Canada’s footsteps. “Canadian authorities banned BPA under public pressure and without any serious scientific study,” said health minister Roselyne Bachelot during an inquiry at the French national assembly in March 2009.
“The precautionary principle is a principle of reason and under no circumstances a principle of emotion,” she said, adding: “It applies when there are no reliable studies. Here, there are reliable studies, which conclude, with current scientific data, that baby bottles containing this chemical compound are innocuous.”
No one is or should be suggesting that BPA is entirely environmentally benign. Science should interrogate all novel theories that might point to new ways to evaluate chemical toxicity – whether it’s BPA or vitamin C. Like other useful chemicals, BPA is so widely used that regulators should continue to vigorously explore whether its effects on children are serious enough to warrant modifications in policy. But that does not mean acting precipitously based on undocumented fears.
To navigate the complexities of modern society, we need standards and established systems – objective science – to guide us in weighing the benefits and potential hazards of chemicals, drugs, whatever. But the moment we abandon standards for fashion or under political pressure, no matter how superficially attractive that may seem, we place in danger the entire system of checks and balances. We upset that at our own peril.