Poisoned Plastic?

By Jim McVeagh 10/01/2010


Yesterday’s Weekend Herald contained a couple of articles on Bisphenol-A, otherwise known as BPA. BPA is used in the manufacture of polycarbonate plastics – the commonest plastic used to make drink bottles and linings of cans. There have been studies in rats and mice that show that BPA causes altered sexual development, aggression and obesity. Studies in humans have generally been equivocal. Canada, the US and Europe have banned the use of BPA, at least in babies bottles. The question now would be whether New Zealand to ban it too.

Frankly there are far more noxious substances in our food than BPA, so it seems a little strange that we should be focussing on this so much. But there is no doubt that this particular substance is a concern. The animal data is pretty consistent. Tracey Barnett in her follow up article on this tries to make out that the equivocal nature of the evidence is a conspiracy:

Someone noticed that 100 per cent of industry-funded studies found no harm from BPA, but curiously, about 90 per cent of independent studies did find adverse health effects. Maybe we’d better revisit this one, the Americans concluded. That’s where they are now. A decision is due soon.

But don’t hold your breath for quick change. The economic motivator to resist this billion dollar plastic retrenchment from multiple industries worldwide is staggering.

Curb your suspicions, Ms Barnett, there is a simple explanation for the discrepancy, that does not involve evil corporates. The industry funded studies are almost entirely small to moderate epidemiological and human cohort studies (i.e. they involve people); the independent studies are nearly all animal studies. The industry does not deny that BPA causes problems in rats. They are just disputing whether it causes problems in humans. And human studies are, for the most part, unhelpful.

For instance, a recent study on prenatal (before birth) exposure to BPA involving 249 mothers and their children did demonstrate a significant correlation between aggressive behavior at 2 years of age and maternal BPA urine concentrations at 16 weeks pregnancy. So far, so scary. But, as the authors themselves point out, although they did their best to correct for confounding factors, there are simply too many variable to be able to draw firm conclusions beyond the ubiquitous “more studies are needed”. The authors were concerned by the great variability of toddler behaviour (were they really measuring “aggressive”?) and the fact that they did not adequately assess maternal psychiatric profiles or correct for maternal/child relationship dysfunction. They also point out that BPA has a short half-life in the body, so 16 week maternal urine BPA does not represent the pregnancy-long exposure to the chemical accurately.

None of this is to criticise this study which was well done, as such studies go. But it does illustrate the great difficulty of ascertaining the long term effects of exposure to a low dose potential poison. Complicated does not even begin to describe it.

And as complex as the studies are, the situation in the day-to-day world is even more complex. On the face of it, it would seem that this is a simple decision. BPA could be toxic. There are alternative plastics that do as good a job, the commonest being Polyethylene terephthalate (PET) and the cost difference to the consumer is very small. Why not ban BPA, just to be safe. As Barnett puts it:

Let’s be clear. Nothing is proven yet. But it feels damned good to take initiative for our own health

Well, hang on. Every person with a factory turning out polycarbonate products stands to be put out of business. It would be nice to have some real facts before rendering them bankrupt. And even if economic disruption is discounted because “health comes first” (even though the risk is really unknown), there is no guarantee that the alternatives will be safer. A recent review of the chemistry associated with PET containers suggests that phthalates and antimony are leeched from the plastic and both of these could have similar endocrine disruption effects to BPA. Changing to PET linings in cans, as the Japanese have done, may actually not improve matters. There is no guarantee that another plastic will be safer.

This is a matter that needs to be approached in a sensible manner. Hysterical denunciations, like this below from Breast Cancer UK, help no-one.

Breast Cancer UK says there is “clear and compelling scientific evidence” that links BPA, an organic chemical compound used for the last 50 years in the production of a wide range of plastic products, with “increased risk of breast cancer and other chronic conditions”.

The evidence is neither clear, nor compelling (unless you are a mouse).

The MacDoctor provides below some simple advice for New Zealanders in the meantime.

  1. Don’t microwave polycarbonate plastic food containers. Polycarbonate containers that contain BPA usually have a 7 inside a triangle on the bottom
  2. Use as little canned food as possible. Frozen foods are generally better for you anyway.
  3. Don’t worry about BPA in fizzy cool drink cans. If you are drinking that stuff, you have bigger problems than BPA!
  4. Make sure your baby bottles are BPA-free (it will usually say this on the carton)
  5. Glass is a generally safe container for all storage but I would not pay the premium for glass bottles, simply to avoid BPA.

And remember, there is NO evidence that BPA is the least bit dangerous to adults. Not even equivocal evidence. While young children should probably limit their exposure to BPA, it is simply not worth the mental energy of adults to worry about BPA exposure of themselves. Its almost like worrying about being killed by a meteorite.

Chill out.

Have a Coke   :-)

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