The health-scare headline of the week: "Americans found to have twice as much bisphenol A in their bodies as Canadians."
BPA, as it is known, is a widely-used chemical found in baby bottles, containers, CDs, car dashboards and even in dental sealants. A new survey finds that Canadians on average have about 1 part per billion of BPA in their urine, while Americans have twice that amount.
"That's bad news for Americans," observes Mother Nature Network News. "Scientists are worried about BPA," writes the Toronto Globe and Mail.
But most scientists are not worried and do not see this survey as bad news. In fact, it's not news at all. Almost without exception, the hundreds of media outlets that have run with this story have failed to mention that regulatory scientists throughout the world have uniformly concluded that these levels of BPA are so miniscule as to be basically harmless.
"Finding a measurable amount of bisphenol A in the urine does not mean that [it] causes an adverse health effect," the Centers for Disease Control and Prevention reported recently, noting that it is found in more than 90 percent of Americans but is "excreted in the urine within 24 hours with no evidence of accumulation."
Exposure vs. Effect
When it comes to stories on so-called toxic substances, the public discourse seems infected by a malady worse than microscopic residues: chemophobia. Webster's defines chemophobia as the irrational belief that "chemicals" are bad and "natural" things are good. Labeling a chemical "toxic" or a "contaminant" is meaningless. Toxicity is a question of degree; exposure is different from effect.
It's critical to examine the consequences of banning a particular chemical. Among its myriad uses, BPA can be found in can liners that increase the shelf life of food and prevent botulism, which is a genuine health threat. There are no effective substitutes. Ban BPA and people are likely to die.
Many activists claim that dental sealants made with BPA can act as a "hormone disruptor." The science says otherwise. According to a 2010 Harvard study, the one-time exposure to BPA that occurs when sealants are put in is only one-fifth to one-half the exposure a child faces daily from environmental sources. "We believe the high preventive benefits of sealants far outweigh the risk," concludes pediatric endocrinologist Abby Fleisch.
"Based on current research, the [American Dental Association] agrees with the authoritative government agencies that the low-level of BPA exposure that may result from dental sealants and composites poses no known health threat."
The FDA, under President Obama, has rejected calls to restrict the use of BPA, noting that its benefits outweigh its risks. When asked last year whether it was harmful to pregnant women or children, deputy commissioner Dr. Joshua Sharfstein didn't mince words: "If we thought it was unsafe, we would be taking strong regulatory action." Sharfstein's view is in line with international regulators. Not one science-based agency in the world has called for a ban of BPA. (It was restricted for some uses in Canada -- when bureaucrats overruled Health Canada's science advisory board, which concluded that there was not sufficient evidence to justify a ban.)
But not Cranor. He argues that "molecules are harmful." The problem with this attractively simplistic thesis is that everything is made of molecules and chemicals. Apples, bananas, basil, broccoli, cabbage, citrus fruits, mushrooms, turnips, and many more foods contain naturally occurring chemicals that are toxic -- they cause cancer at large lifelong doses in laboratory rodents. Tofu is more estrogenic than BPA.
Outbreak of Chemophobia
This distressingly familiar chemophobic narrative derives from the precautionary principle --the notion, popular in Europe, that a substance can be banned even absent hard data and a cause-effect relationship if it is perceived as potentially harmful. The precautionary notion is not a scientific standard. It is an attitude rather than the kind of clear-cut rule that generally forms the basis for regulation. In its most extreme applications, tradeoffs are not considered, such as the harm that might be caused from restricting a particular technology or the potential danger of substituting an untested substance for a thoroughly evaluated one.
More than anything, this precautionary notion gives legislators and politically-appointed regulators -- some with a limited scientific IQ -- the freedom to pick and choose which substances to restrict. And it threatens to replace the risk standard long used in the U.S. and in most of the world.
Risk describes the probability of genuine danger. The key is setting an appropriate threshold. Until now, regulators have been ultra-cautious, especially in America -- establishing limits hundreds to thousands of times more restrictive than those suggested by studies on sensitive laboratory animals. Under long standing international protocol, as long as a substance doesn't violate a data-defined threshold with a cushion in the tens or hundreds of thousands, it has been allowed onto the market.
But with recent advances in bioanalysis, scientists are now able to isolate a thimbleful of a liquid poured into Lake Erie. Our technology is so advanced that parts per trillion can often be identified in pure water used for liquid chromatography. Exploiting unscientific fears of trace levels of chemicals, activists are putting pressure on regulators to set thresholds of what can be measured not on what is potentially dangerous -- without evidence that current standards are inadequate.
The FDA, EPA and USDA have to evaluate hazard and risk when making decisions on what to restrict and at what level of usage. Recently, the EPA announced it is reviewing the limits on perchlorate. The chemical is valuable when used as a key component in rocket fuel or to treat thyroid disorders, but can have health impacts at very high levels of exposure -- which is rare. In other words, it offers benefits and risks. Weighing them is what sensible regulation is all about. (Let's hope the government's recommendations are based on the evidence and not on fears.) But 'sensible balance' is not what some health and environmental campaigners advocate.
Consider the case of nuts. Many natural fungi produce mycotoxins that affect up to 25 percent of the world's nut supply. One of these, aflatoxin, can be a significant factor in causing cancer, and infects up to 15% of California's almond crop. The most effective and efficient containment strategy is to use insecticides to control insect crop pests, which would otherwise injure the nuts, seeds or grains, thus providing points of entry for the fungal pathogens to infect the mature or harvested crop and produce the toxins. Yet environmental campaigners adamantly oppose that method of control, in effect ignoring a natural toxic chemical while taking an inflexible stand against a synthetic protective chemical. Such trade-offs mean very real risks to consumers, which can result in injury and even serious illness, and some people may die.
They also have launched zealous campaigns against weed killers that are necessary for crops to flourish. For example, the common triazine herbicides, such as simazine and atrazine, have become central targets of anti-chemical campaigners. Yet, as one example, published studies show that legal limit on atrazine exposure has an extraordinary safety cushion -- up to 1,000 times or more what advanced scientific studies has determined is safe for humans. But many environmental campaigners, citing controversial and contested studies on amphibians, lobby for a ban of triazines, atrazine in particular.
What do the frog studies show? Lab experiments by one prominent researcher who exposed clawed frogs to lower doses of atrazine produced males with ambiguous genitalia and squeaky, soprano-like croaks -- hermaphrodites. University of California endocrinologist Tyrone Hayes labeled atrazine an "endocrine disruptor" -- a term now used by chemical critics to stigmatize many chemicals not found to be carcinogenic.
Critics of atrazine have long contended that atrazine disrupts both the fertility and the normal sexual development of amphibians, which suggests potential danger to humans, particularly pregnant women or young children. But no studies actually show or even suggest that. Many plastics, as well as many natural substances such as clover, many fruits, and soy --together called phytoestrogens -- subtly alter the way our hormones work. They key issue is: at what level of exposure.
Moreover, the EPA and the various independent scientists from around the world have doggedly tried to replicate Hayes's findings to no avail. Biologist Werner Kloas of Humboldt University in Berlin, who believes that chemicals should be banned for precautionary reasons if the evidence is ambiguous, found no impact on clawed frogs at concentrations comparable to those investigated by Hayes.
Most recently, David Skelly, professor of ecology at the Yale School of Forestry & Environmental Studies, who is a firm proponent of the "atrazine retards frogs" school, was flabbergasted to discover that the deformities he found in field studies were actually lowest in farmlands, where atrazine is often used, as compared to cities and suburbs -- a direct challenge to the activist hypothesis.
"[W]e found that in those kinds of landscapes where corn is being grown, the great majority of the ponds we sampled didn't have any deformities at all."
Skelly's findings underscore one of the fundamental truths of science: data and context are more important than ideology, however well motivated. Branding any chemical as a toxic "endocrine disruptor" is about as useful as describing a car as "fast." Terms such as "neurotoxic" or "endocrine disruptor" sound alarming, but they say nothing about how much of a substance might be problematic. Relative to what? Under what conditions in the real world? The question for regulators remains: What level of exposure to a substance causes a deleterious effect? As Paracelsus, the father of toxicology, observed, "All things are poison and nothing is without poison, only the dose permits something not to be poisonous."
Scientists at the World Health Organization, whose mandate is to protect the vulnerable, last year rejected calls by activists to ban atrazine. Recognizing its invaluable role in modern agriculture -- atrazine significantly increases crop yields and lowers overall use of pesticides -- and basing its decision on new health studies, the WHO actually softened its limits to 100 parts per billion in groundwater. Its new precautionary standard is now 33 times higher than the 3ppb in the U.S.
The WHO was wise to consider the tradeoffs, because banning effective chemicals always has consequences. Agricultural chemicals are among the most scrutinized and regulated of all technologies. In Europe, which is already more restrictive than the U.S., governments are phasing in precautionary criteria that could blacklist 22 chemicals-- about 15 percent of the E.U. pesticide market. Some environmentalists are pressuring U.S. regulators to abandon a risk-based approach for this more politicized European standard. That would be a mistake.
The bottom line is that in order to maintain healthy crops, farmers fight a constant battle against insects, fungi and plant diseases, as well as weeds (which compete with crops for water, nutrients, and light). Advanced chemical technologies have helped to prevent infectious diseases and to enhance crop yields. These are the drivers of the Green Revolution, which has dramatically cut world hunger over the past 60 years.
Chemicals often get a bad rap. In the case of BPA, atrazine and other chemical with demonstrable societal benefits, are we prepared to trade off the certainty that banning them will damage health against the long-shot possibility, based on contradictory studies on rodents or frogs, that a chemical might be harmful over a lifetime of exposure? That said, scientists must remain open to new evidence. We are developing sophisticated tools to evaluate exposure to chemicals, including examining their impacts on genes and hormonal system. If the weight of evidence shifts, we have to be prepared to tighten regulations.
But acting precipitously based on public anxiety is a dangerous precedent. Bans make sense only if we gain identifiable health or environmental benefits in exchange. It's becoming increasingly difficult for the public to distinguish genuine risks from chemophobia. Advocacy groups and their enablers in the breathless media often compound the confusion. With the stakes so high, scientific literacy is no longer a luxury.
Jon Entine, editor of Crop Chemophobia: Will Precaution Kill the Green Revolution? (AEI Press, 2011), is senior fellow and director of the Genetic Literacy Project at the Statistical Assessment Service (STATS) at George Mason University.
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