the precautionary principle is flawed

October 1, 2012 at 10:28 am | | news, science and the public

I’ve always warned against the Precautionary Principle, mainly because it has a fatal flaw: no one applies the same principle to the alternatives. The Precautionary Principle assumes a product (or medicine or technology) is harmful until it is proven to be safe, instead of the other way around. This sounds nice, but the problem is that it doesn’t take into account the dangers of the alternative products (or medicines or technologies). That is, at least how most consumers apply the principle.

I warned against this when the BPA kerfuffle emerged. Many people started to get concerned about bisphenol A, which is a monomer for polycarbonate used in many plastic bottles. Some BPA can leach from the plastic into food or liquids, and there has been some evidence that it may mimic hormones in the human body and may have negative health effects especially in children. So everyone started banning BPA bottles and switching to other materials. The main alternative is “BPA-free” plastics. When this happened, I asked, “But what are those plastics made of??”

Basically, everyone switched over from a known product (polycarbonate) that might have some deleterious effects, to a proprietary polymer (Eastman’s Tritan) that we knew nothing about. And everyone felt safe.

But what if Tritan is a thousand times more dangerous? What if the glass bottles that some people switched to leaches lead (although I doubt many parents are giving their kids crystal to drink out of)? What if those steel water bottles put chromium into your water? (The aluminum ones like Sigg are coated with a plastic, anyway.) It doesn’t really make tons of sense to throw away your old water bottles to buy brand new ones that have a new, proprietary plastic that can leach new, unknown chemicals into your water.

C&E News has a story about Eastman’s Tritan and it’s possible health dangers. We should all throw away our new water bottles and start drinking out of another unknown material so another company can make billions off of our fears. Or just start drinking directly from the faucet.

The only correct application of the Precautionary Principle is to have someone measure the safety of all the materials used to make water bottles and baby sippy cups and weigh the dangers against each other. Maybe Eastman should pay for that. ;)

(That said, I must admit that I drink out of glass, a coffee mug made in China, and a steel water bottle. Who knows what I have in my body.)

Thanks for the tip, Chemjobber.


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  1. Sam!

    Actually, I agree with you. That said, it’s my vague gut feeling that BPA (structurally) could be bioactive (phenol, etc.), while the Tritan monomers (cyclohexanediols, cyclobutanes) are less likely to be. Don’t know if that’s true, of course.

    Comment by Chemjobber — October 1, 2012 #

  2. good point.

    Comment by sam — October 2, 2012 #

  3. I completely agree that the “BPA from plastic bottles” was totally overblown – and the wrong place to fight BPA.

    First of all, it seems that BPA is “bioactive”, but not in the way many people thought. Most commonly it is thought that BPA might act as an Estrogen – but if you look at the structural formula, BPA is very similar to the thyroid hormones T4 and T3.

    And secondly, the amount of BPA that is *contained* in water bottles is minuscule compare to the amount of BPA you could *pick up* via thermal paper, which used to be drenched in BPA. That was changed some time ago without you hearing much about it – go figure.

    Comment by Tony Mach — October 6, 2012 #

  4. So you want us to test all stuff first before it hits the market, rather than remove it upon first sign of trouble? That is even more precautionary than the precautionary principle. It’s the uber-precautionary principle!

    I think the public was urged to switch from BPA to whatever else in that no studies had yet to suggest that “whatever else” is harmful.

    I guess the basic question could be put like this: do we test each field before walking on it to determine whether it’s a minefield, or do we go ahead and walk any field until we lose a foot?

    Seems stuff like medicine requires pre-walk minefield testing; stuff like water bottles, more the wait-till-the-foot-goes-kerplooey approach.

    Comment by jordan — October 9, 2012 #

  5. my point is that if you’re going to apply the precautionary principle, you must also apply it to the alternatives or it’s a useless principle. people think that they are safer, but they’re not. i think what you call “uber” is just the actual precautionary principle, applied correctly. :)

    Comment by sam — October 9, 2012 #

  6. Unless studies indicate that the alternatives pose harm, the precautionary principle won’t apply.

    Comment by jordan — October 10, 2012 #

  7. then it’s a stupid principle. say you’re standing in a minefield. a mosquito is about to land on you. should you run to another spot to avoid a mosquito? the precautionary principle would say yes, to avoid the possible harm from the mosquito. but then you’re way more likely to get blown up by an unknown mine. i think that rational risk analysis would weigh risks against the risks of harm from the alternative options, not just assume that an alternative is always more safe. every action (or inaction) has a risk of harm.

    Comment by sam — October 10, 2012 #

  8. The principle urges action (or inaction) only where risk is indicated. It also allows for balancing the risks indicated among alternatives. But it does not urge caution toward the complete unknown. Clarifying: Are you suggesting we shouldn’t move away from an indicated risk in favor of a complete unknown?

    Comment by jordan — October 12, 2012 #

  9. I drink all of my water directly from the kitchen faucet.

    Comment by Kevin Kent — February 8, 2013 #

  10. Kevin, that’s just ’cause you’re too lazy to grab a glass.

    Comment by sam — February 11, 2013 #

  11. […] argued in the past that the Precautionary Principle is logically flawed, even dangerous. A recent article on Slate gives a great job giving an example of when the Precautionary Principle […]

    Pingback by Everyday Scientist » great chemophobia article in Slate — February 11, 2013 #

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