We thought that everyone could agree that the year-round availability of low-cost, appetizing and healthful fruits and vegetables to school-kids is a good thing. We were naive.
According to a study published in September in an obscure journal, schools are exposing kids to potentially dangerous levels of toxic chemicals from food packaging because of "schools' efforts to streamline food preparation and meet federal nutrition standards while keeping costs low."
The study, published in the Journal of Exposure Science and Environmental Epidemiology, was performed by Jennifer Hartle, a Stanford University postdoctoral research fellow, and her colleagues from the Johns Hopkins University Bloomberg School of Public Health. The study design was simply to visit school kitchens and interview food service staff. Not surprisingly, they found that kids were eating fruits and vegetables that had been packaged in cans and plastic, and that small amounts of the chemical bisphenol A (BPA) migrated from the packaging into the food.
Then the investigators "modeled" the exposures: "Exposure scenarios were based on United States school nutrition guidelines and included meals with varying levels of exposure potential from canned and packaged food."
So what's the worry? The researchers claim that "even small amounts" of the chemical BPA in food packaging can be harmful by causing "hormone disruption." However, the FDA (which regulates such substances as "indirect food additives") and food safety agencies around the world have thoroughly investigated the issue—and come to starkly different conclusions.
The agency's webpage (most recently updated in June) dedicated to the issue states, "FDA acknowledges the interest that many consumers have in the safe use of Bisphenol A (BPA) in food packaging. FDA has performed extensive research and reviewed hundreds of studies about BPA's safety. We reassure consumers that current approved uses of BPA in food containers and packaging are safe."
Did Hartle's article allege that schools expose kids to levels that exceed the already extremely conservative federal standards? No.
Did it show that that exposure is sufficiently high to have an effect? Again, no.
But sloppy reporting from gullible writers and bloggers might cause one to believe otherwise. Consider this from the Baltimore Sun: "students could be getting anywhere from a negligible amount of BPA up to 1.19 micrograms per kilogram of body weight." But in even this modeled estimate of the most-exposed child, the higher exposure is still "negligible." According to the EPA, 50 micrograms per kilo of body weight is a safe intake level. Thus, a more accurate statement would be, "students could be getting anywhere from a barely detectable amount of BPA up to a still-negligible 1.19 micrograms per kilogram of body weight–less than one-twenty-fifth of the amount felt to be safe."
The concept that dose is critical to whether toxicity is observed is not rocket science. Large amounts of nutmeg or licorice are notoriously toxic, but the amounts ordinarily consumed are perfectly safe.
So if kids aren't exposed to levels of BPA that exceed federal (or even hyper-cautionary European) standards, what's the problem? In a Stanford press release, lead author Jennifer Hartle concedes that, "While most students would not consume the maximum amount, those who do would take in more than half of the dose shown to be toxic in animal studies in just one meal." She–and certainly her more senior coauthors–should know that it is tenuous to extrapolate laboratory animal studies to dose limits in humans if the animal studies are inconsistent with what we know about how effectively humans metabolize BPA in the real world.
But it seems that to Hartle, scientific rigor isn't really the issue, as evidenced by her rhetorical questions: "If this is an avoidable exposure, do we need to risk it? If we can easily cut it out, why wouldn't we?" That view is a manifestation of the so-called "precautionary principle," which implies that we should strictly regulate or ban any product, process or activity until it is shown to be absolutely safe. Well, it's fine to advocate that we look before we leap. The trouble is that the Hartles of the world want us never to leap.
The problem with the precautionary principle is that it fails to consider the risks of excessive regulation or bans. For example, although exposures to many chemicals are theoretically "avoidable," such avoidance comes with trade-offs. We could avoid allergic reactions to penicillin by banning it, and eliminate the carnage of high-speed car crashes by setting the speed limit at 30 miles per hour, but. . . you get the point.
BPA used as a coating in canned food prevents botulism and other bacteria-caused illnesses. BPA's protection of canned goods allows schools to provide more fruits and vegetables, by safely preserving them in cans all year round, and at low cost. A sound scientific approach would call for an estimate of the comparative risks to schoolchildren, with and without the availability of BPA. But none of this seems to matter to Hartle and her collaborators, who are, in effect, looking through the wrong end of the telescope.
That may be why Hartle (as quoted in the press release) wishes us not to think about the scientific or economic tradeoffs or the dictates of sound epidemiology but instead informs us that, "The bottom line is more fresh fruits and vegetables...There is a movement for more fresh veggies to be included in school meals, and I think this paper supports that." Sounds as though that was the agenda.
The study does teach us an important lesson: Academics and scientific journals are susceptible to platitudinous advocacy-driven science that sheds more heat than light on an issue. And newspapers and (especially) blogs report it uncritically. They all need to do better.
Jeff Stier is a senior fellow and the director of the Risk Analysis Division at the National Center for Public Policy Research. Henry I. Miller, a physician and molecular biologist, is the Robert Wesson Fellow in Scientific Philosophy and Public Policy at Stanford University's Hoover Institution; he was the founding director of the FDA's Office of Biotechnology.