Phthalates – Are They Safe?

Phthalates-are-they-safe

An artist’s impression of a phthalate

I suppose I should start with how they are pronounced.  The first four syllables are pronounced in the same way as the first two of thought.  So not too hard to say.   It is phthalates in the plural because phthalates are a family of chemicals that all share a common structure.  You can find the details with a bit of googling if you are interested.

But for the sake of my argument all you need to know is that if you could see a phthalate molecule up close it would look like a ball with two strings attached to it.

Phthalate Structure

The ball is the distinctive phthalate bit, and the strings are strings of carbon chains similar to those found in a great many other molecules.  These strings can be any length in theory so there are an infinite number of potential phthalates.  In practice there are about thirty that get used for various purposes.

The reason that people are concerned about them is that the shape of some phthalates has a resemblance to sex hormones.  This means that potentially they could get into the body and disrupt the normal functioning of the endocrine system.  This could be serious because the endocrine system is intimately involved in many of our most important bodily processes.  In particular the development of infants during pregnancy is a very delicate system – one that goes wrong often enough of its own accord.

Are Phthalates Endocrine Disruptors?

There are a couple of things that follow on from this.  The first is that relatively low concentrations might be effective.  Hormones themselves work at very low concentrations, so it doesn’t take a huge amount to have an effect.  So that makes caution important.  The other thing is that the effect is going to be highly dependent on the shape of size of the molecule.  This means that the problem is likely to be limited to a single type of phthalate or at worst a relatively limited number of phthalates.  This is two edged.  It means we can’t assume because a study shows a particular phthalate is safe, that a very similar one is also safe.  It also means that just because one phthalate has a problem that doesn’t mean there is a general problem with all phthalates.

So this is a tricky problem. The only good point is that if you read anything where the author doesn’t distinguish between different phthalates then the chances are they are either badly informed or deliberately intending to misinform you.  So that is handy.

Phthalates – the Science

Phthalates certainly can cause damage, and there are a number of papers that give details of how harmful this damage can be. There is for example one that shows a couple of the phthalates affecting the rate of testosterone production in growing rats.

But there are lots of chemicals that can be harmful at high doses. This includes plenty of things we handle quite safely every day and never give a second thought. It’s always a question of how much. The well known saying. ‘the dose makes the poison is very true. The question is do the effects we see at high levels occur in the same way at the kinds of levels we are actually exposed to when we use a cosmetic? Frustratingly we have very little data on this.

There is one paper that shows very low levels of phthalates indeed having an effect on development. The researchers showed a reduction in the weight and a change in function of the organs of pregnant rats exposed to tiny levels of one of the phthalates. Would those changes have translated into birth defects? We don’t know, because the rats had to be killed to get the measurements. But rats treated with the same dose were mated and went on to produce normal offspring.

I have to say I absolutely hated this paper. Scientific papers are supposed to be neutral reports of the findings. This one obviously had an axe to grind, with extensive discussions of what it all meant and even going into legislation. We all know you be wary of anything once politics gets involved.

Although it has been written up in a way to make the case against phthalates as strong as possible, in reality it doesn’t get us very far. Rats aren’t humans and specially bred lab rats probably aren’t even especially typical even of rats. The effects noticed weren’t very great and with no independent confirmation even they could easily be a one off.

So What Is My Opinion of Phthalates?

So the science isn’t all that clear – it rarely is.  What is my advice?  I don’t think there is a high chance that phthalates in general do any harm, and the case against a few specific ones has yet to be made convincingly. We probably all have much more important things to worry about in our lives.   But our brains don’t work like that of course.  If you look at the statistics you find that the risk of coming to harm walking around a city on your own late at night is pretty low.  Few of us would do so even so.  The extremely low probability of being the victim of a violent crime is balanced by how bad it would be if you were the person who was unlucky.  So we are naturally and understandably worried at even a very small chance of a chemical doing us any harm.  Our knowledge is increasing all the time.  It may well be that in the future we can be sure they are okay, but for now why not be neurotic. I don’t trouble to avoid phthalates myself, but I could understand why somebody might.

References

Abnormalities in rat ovaries

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2265047/

Review paper

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http://www.ncbi.nlm.nih.gov/pubmed/18949836

Phthalates affect rat testes

http://www.ncbi.nlm.nih.gov/pubmed/16102138

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3 Responses to Phthalates – Are They Safe?

  1. Ed says:

    While you’ve debunked the rat studies as having a preconceived and political agenda, haven’t there been a number of studies on children done since then?

    Are expectant mums “neurotic” to give phthalates a miss while scientists are still investigating the link with cryptorchidism and other male reproductive disorders?

  2. Colin says:

    I don’t know of any studies done on children Ed. I’d love to see them if you can find them. I think the question can only be answered by some really diligent epidemiology. That is a tough business, but who knows what can be done with statistics in the future with all the computing power we are building up.

  3. Ed says:

    I found a fair few by doing a search on Google Scholar.

    I’m not a chemist or a doctor so not really in a position to judge which are good studies and which are not. That’s why I asked you!

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