I can tell how this story is going to play out – researchers found that there are little bits of plastic in your bottled water. Next up will be an insistence that we’ve all got to stop using plastic bottles, we must scour the oceans of their residue, and while we’re at it why not stop using plastic altogether? This is not the correct lesson to be drawing from this finding – Instead, be glad that we’re getting better at measuring things.
The paper itself is here and the first thing to note is that this isn’t at all about the general water supply being polluted. The paper is quite clear on that – the water in plastic bottles seems to have more bits of plastic in it than tap water. It’s something about putting tap water (which is what some companies do, after a bit of fiddling with it) into plastic bottles which is the issue here. The plastic found is mostly the type used to make the caps, so the logical conclusion is that screwing the cap water bottles puts plastic in our water.
There are two threads, we put them together tightly, some small pieces break off. And?
Well, the correct response to ask is “how much of this plastic is in there? Enough to concern us? Or the sort of amount that we really shouldn’t be worrying ourselves over?” The answer there is ever so slightly difficult.
First, the paper doesn’t give us the concentration in the usual terms. It tells us how many pieces of plastic per liter. It gives us two lengths of plastic that were measured. But it does not tell us how wide each piece was – we therefore cannot estimate how much plastic per liter, only how many pieces, which isn’t all that useful. Say we were considering arsenic, something we really should worry about in the water supply. We’d not be all that informed by the news of how many pieces there were, we’d want to know the concentration.
Still, estimates can be made – and they are that, just estimates. Talking to people who know this sorta stuff, I’ve had such estimates of one part per billion up to perhaps 60 ppb. We still don’t know whether that’s a lot though, do we? Because we’re not used to this sort of measure. Both the World Health Organization and the US’ own Environmental Protection Agency say that arsenic in drinking water shouldn’t be above 10 parts per billion, that same unit measure. It’s also true that such limits are usually set by a pretty basic rule of thumb. Take the absolute minimum level we know that might possibly affect anyone, then divide it by 10 – 10 at minimum, usually by a larger number.
So, for a known poison to humans (arsenic) the minimum level we can think of which even might, possibly, over long periods of time, harm anyone at all, is 100 parts per billion. Plastic we know is very largely inert, doesn’t harm humans as a poison at all, and the levels of it are lower than that known of poison’s theoretical damaging limit.
Hmm, no, we’re not going to worry over this, are we? Or at least we shouldn’t be worrying over it.
The real story here is in fact something quite different. It’s only in recent years that we’ve even been able to test things for parts per billion. Back a couple of decades ago, parts per million were all we worried about. Even then – I’ve worked with trying to purify substances to this sort of level – 1 ppm was considered a most unusual thing to worry about.
Really, this is about how much better we’re getting at that science thing of testing the contents of bottles, and nothing more to worry about.
Tim Worstall (@worstall) is a contributor to the Washington Examiner’s Beltway Confidential blog. He is a senior fellow at the Adam Smith Institute. You can read all his pieces at The Continental Telegraph.
