Media Overstating Phthalate Risk Say Doctors

December 18, 2007

Trevor Butterworth

In the op-ed – “Stop Scaring Us” – for the Los Angeles Times, Henry I. Miller, a physician and molecular biologist, and fellow at Stanford University’s Hoover Institution, argues that extending California’s ban on phthalates in children’s toys across the nation is an act of folly:

“Now, Sen. Dianne Feinstein (D-Calif.) is eager to expand California’s folly to the entire nation. Undeterred by the judgment of experts but swayed by a few experiments with rats and a single flawed epidemiological study, Feinstein has introduced a bill that would ban six types of phthalates in toys. These chemicals are widely used to soften plastic toys and are found in shower curtains, traffic cones and scores of other common items. They also have crucial applications in surgical instruments and intravenous tubing.

Unfortunately, Feinstein’s legislation ignores the basic principles of toxicology. For starters, a rat’s metabolism differs significantly from a human’s. Although rat studies may be useful for suggesting what sorts of toxicity to look for in humans, often they do not predict effects on humans. Indeed, the toxicity of phthalates in rats appears not to be replicated in humans or other primates.

Second, the dose makes the poison. This means that the mere presence of something in the body does not imply harm; one needs to know the dose and length of exposure, what the substance does (if anything) in the body, how it is disposed of and so forth. Virtually any substance, including water, can be toxic at high enough levels.”

Miller also notes a key point that most journalists writing about this topic seem willfully blind to: When Europe banned phthalates, it did so against the recommendation of its own panel of scientific advisors.

While the Hoover Institution association will surely be used by some journalists and many environmental activists to dismiss Miller’s criticisms as coming from a pro-industry perspective, Dr. Ben Goldacre delivered a not entirely dissimilar message in the Guardian newspaper over a week ago.

The “Bad Science” busting doc said the risk from phthalates has been overhyped by media – although he is a marginally more kind to the Shanna Swan study in Environmental Health Perspectives that launched this health scare, aided by journalists who did not appear to actually understand what the study said, why it was limited, and why one of it’s key contentions was not accepted by a national panel of reproductive health experts.

“Phthalates are all different, but some have been shown at high concentrations to have harmful effects in laboratory animals, they may block the effects of male hormones, and in one OK-ish study – the results of which have been overstated in many quarters – phthalates have also been associated with borderline effects on genital development in foetuses.”

To some, eliminating a “borderline effect” is a precaution worth taking; but as Miller notes, because phthalates do so many essential jobs in plastics, banning them will simply mean they are replaced with other, less well-tested chemicals. And that is why bad science makes bad policy.


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