07/12/2007 05:59 pm ET Updated Nov 17, 2011

Should California Ban Cancer-Causing Carrots?

I'm not sure I understand why Fiona Ma, a qualified tax accountant with a fondness for Brit Goth music, is so afraid. As a California State Assemblywoman, she has been pushing and pushing to have phthalates banned from children's toys, when the evidence for danger has the soft, hazy quality of a virtual hill of beans. Of all the health risks facing children in California, being poisoned by sucking on a rubber duck is one that remains solidly hypothetical; and even though science is forced to refrain from absolute certainties when it comes to estimating risk, the number of studies showing that these chemicals actually induce birth or reproductive defects, cancer, early onset puberty or neurological damage in humans or infants is, so far, a numerically unequivocal zero.

Even as a precautionary measure, as a worse-case scenario to be avoided based on the most far-reaching speculation on the dangers of low-dose exposures to chemicals, the ban has about as much rational compulsion as a ban on carrots and other vegetables. Many veggies contain caffeic acid, which is a "suggestive" human carcinogen based on rat studies; if we eat lots of veggies, then maybe we'll get cancer. Shouldn't we avoid that risk too?

The point is that anything can poison rats if they are forced to eat enough of it; but that doesn't necessarily translate into a *real* risk to us -- or a risk that is worth avoiding given the evident benefits of eating vegetables. It's the dose that makes the poison, and you have to dose rats with a lot of phthalates to make them sick.

When it comes to the specific phthalates that make plastic toys flexible, my colleague at STATS, Dr. Rebecca Goldin, has noted that the Consumer Product Safety Commission rejected a request in 2003 for a nationwide ban on the phthalate most widely used in children's toys -- DINP -- because the pathway to exposure -- sucking -- didn't add up to a clear and present danger.

"Total mouthing time for babies 3-12 months old is about 10 minutes per hour, including pacifiers, bottle nipples, parts of their own bodies, and any other device (designed for sucking or not). For older babies, the numbers go down. Pacifiers constitute most of babies' sucking time (about a third) and their own body parts are preferred next. Soft vinyl toys containing DINP were sucked on for under 11 seconds per hour, or under 5 minutes a day. Even the most avid suckers (in the 99th percentile) were chomping at their DINP toys for at most 12 minutes per day. A baby would have to suck for about ten times as long before they could consume enough DINP to have any potential adverse effects."

In 2003, the European Union reached a similar conclusion in its risk assessment for DINP: "for infants, combined exposure which is mainly related to exposure from toys and via the environment is not considered of concern." Meanwhile, the other phthalate found in children's toys -- DEHP -- has, like DINP, not been associated with any reproductive risk, even by the one study conducted since 2003 that has ended up powering the legislative movement to ban phthtalates.

This study -- Decrease in Anogenital Distance among Male Infants with Prenatal Phthalate Exposure -- was widely reported by the media as having found a link between phthalates and genital defects, and it has been cited by environmental groups and activists ever since as the evidence for why there should be a ban.

What the media didn't report -- and the San Francisco Chronicle continues to ignore in calling for the ban to pass next Monday -- is that none of the children in the study had *any* genital defects, that the author of the study's math didn't quite add up, that the study found no correlation between the specific phthalates in toys and a biomarker for reproductive risk, and that, later, this key inferential biomarker was rejected by the Center For the Evaluation of Risks to Human Reproduction.

Compared to the actual risks from fetal-alcohol syndrome, childbirth, second-hand smoke, particulates from smog and car pollution (widely correlated with increases in asthma), poor diet (the fastest way to poison your child given the rising numbers of children with diabetes), assault (homicide claimed 33 children aged between 1 and 4 in California in 2004), one could argue that the potential for adverse effects from rubber toys is hardly the most urgent public health issue facing California's children.

Still, the state Senate will get to vote on legislation -- AB1108 -- next Monday, thanks to Ma's Roald Dahl-like zeal; and increasing pressure on those Democrats in the State Senate who have so far refused to endorse such precautionary thinking may ensure it will pass.

But here's the really crazy part: if the ban passes, it won't actually change anything -- at least in terms of public health. At best, it *might* knock a percentage point or two off infant exposure to phthalates, which, as the National Institutes of Health have found, *overwhelmingly* comes from dust and food.