How Safe is our Mineral Water?
Chris - We're talking about environmental pollution and how these chemicals can impact on human and animal health this week. Martin Wagner is at the University of Frankfurt and he and his colleagues have been looking at an oestrogen-like chemical that can leach out of bottles that are made of the substance PET, polyethylene terephthalate. That's the sort of bottles that you buy mineral water in. People are obviously worried as mineral water has become very, very popular in recent years. What could be the impact on their health? Hello, Martin.
Martin - Hello.
Chris - Welcome to The Naked Scientists. Could you tell us a bit about the studies you've been doing to try and find out how these sorts of plastics could be affecting people?
Martin - Yes. Basically, we used an in-vitro bioassay for detecting oestrogenic activity. It's a pretty simple system where you have a genetically modified yeast that expresses the human oestrogen receptor, and thereby, you can use it for detecting all compounds that bind to and activate our oestrogen receptor. Normally, you're using this for effluents of sewage works and just to detect the level of oestrogenicity in the environment that's sampled.
Chris - I see. You have genetically modified a yeast cell so that the yeast cell can see oestrogen and then presumably change colour or something, so that you've got a readout of whenever there's oestrogen, or something that had oestrogen-like effect in water, you can see it?
Martin - Yes, exactly. That's how it works. And since everybody was using it for environmental water samples, we thought, "why don't we test all our favourite mineral water brands and have a look into that?" So it was, in the beginning, more like a fun experiment we did at the lab and of course, we didn't expect to find some estrogenic activity in mineral water because of you know, mineral water is just minerals dissolved in water! But then in the first experiment, we had really highly positive samples. This meant that we were able to detect oestrogenicity in these mineral water samples, and then we took a deeper look into that and we got funding and continued our work here.
Chris - So there are some brands of mineral water that come in plastic bottles. There are others that come in glass bottles. Some come in both. So that would presumably give you a quite neat way to compare, wouldn't it? You could look at the same brand of water in both plastic and glass.
Martin - Yes. What we did was, we just went to the supermarket and we bought 20 samples of 20 brands of mineral water here in Germany, and just looked at the oestrogenicity. Half of it was packed in plastic and the other half was packed in glass bottles.
Chris - What did you find?
Martin - It was quite surprising to us that we found really high oestrogenicity in these mineral water samples and in almost all mineral water samples, you can detect significant oestrogenic activity, 60% of the samples were positive. What was striking to us was that, in most of the water coming from plastic bottles, we detected estrogenicity whereas we only had three waters from glass bottles where we could detect some levels of oestrogen activity.
Chris - So, the assumption is that the oestrogen-like chemicals are coming out of whatever is in the plastic. They're getting into the water and your yeast is seeing them. What does this tell you about how likely they are to have relevant effects in humans. Because obviously, it's one thing to detect a chemical, it's another to demonstrate that it's actually having a physiological effect, in other words, a meaningful effect in the body?
Martin - Yes. That's the Achilles heel of our work that we've done so far. We have only detected oestrogenicity, the yeast can't tell you if it's bisphenol-A for example (it's not very likely that it's bisphenol-A) or other chemicals. It just tells you something activates the estrogen receptor, some chemical. It can be a mixture of different chemicals for example. So far, we haven't identified the chemicals causing this oestrogenic activity in mineral water yet. We're still working on it and it proves, I must say, really hard because you're looking for really low levels, low concentrations of these chemicals. In fact, we don't know what we are looking for, so we have to do an effect-directed chemical analysis, and that's what we're trying to do right now.
Chris - Can you not take the contents of the mineral water bottles and then expose them to an animal which is a bit bigger than a yeast, and therefore see whether they do have at least some effect in animals?
Martin - Yes. We conducted the second series of experiments where we're asking the question whether the plastic bottle is really releasing some oestrogen-like compounds. So, we emptied all of our bottles and put oestrogen-free water in every plastic bottle and in every glass bottle. And then we inserted small little snails, New Zealand mud snails, inside the bottles and we cultured them and took care ofthem for eight weeks. And the thing with the snails is that they are really sensitive to oestrogens. So, if they are exposed to low levels of oestrogen-like compounds, they change their reproductive patterns and we can look at it.
Chris - So you get one group of snails, they're in water in glass bottles.
Martin - Right.
Chris - You got another group of snails in the same water, put into a plastic bottle and kept for two months.
Martin - Yes.
Chris - What happens to the snails?
Martin - After that, we looked at the reproductive output of our snails and we found that the reproduction of snails living in glass bottles was completely normal. But compared to that, snails living in plastic bottles had double the amount of embryoes. So, they doubled their reproduction, just by living in the plastic bottle, and that was for us, at least a strong evidence that some of these oestrogen-like compounds leached out of the plastic packaging material.
Chris - Which is a worry, isn't it? Just to finish off, Martin. Can you comment therefore - obviously, a snail isn't a person - but can you comment on the relevance on this to humans because one thing we're seeing in the world these days is that girls are going into puberty and they're starting menstruation at younger and younger ages all the time. The average age now is about 10. It used to be about 12 and this is within the last 50 years. This is not a genetic change. This is something environmental. Now obviously, people are better fed, but you can't explain all of it on the basis of nutrition.
Martin - I think our mineral water study provides a good example that we're exposed to lots of these endocrine disruptors, these oestrogenic compounds, from different sources. If it's in mineral water, I'm asking myself, is it not also in cheese maybe packed in plastic for example? So there's a lot of exposure going on and we don't know a lot about it. But there could definitely be a causal link there with reproductive problems...