Female hormones in mineral water
It was a major media uproar: in 2009, scientists at Frankfurt University detected alarmingly strong hormonal activity in mineral water. The German researchers employed bioassays to demonstrate that components of the mineral water samples mimicked the female sex hormone oestrogen /1/. ‘We realised that, in terms of hormones, mineral water has about the same quality as waste water in sewage treatment plants’ /2/. With such statements, the researchers set the alarm bells ringing.
But where do these hormones come from? In the case of waste water from sewage treatment plants, the answer is straightforward: besides natural hormones from human urine, synthetic oestrogens from birth control pills also play a significant role – which in extreme cases, can lead to the feminisation of entire fish populations. However, the high levels of oestrogenicity in mineral water cannot be explained as easily. It should be obvious in this case that hormones from human or animal excrement can be ruled out, and at first glance, there does not seem to be any plausible source of hormones in mineral water.
Have PET bottles been falsely blamed?
Various assumptions about possible hormone sources were then made. PET bottles, which were used for the majority of the mineral waters tested, were regarded as the likely suspects, which was possibly influenced by the negative image of ‘plastics’ in general. Certain components of plastics (e.g. certain plasticisers or starting materials for polymerisation processes) can have a structure similar to the natural oestrogen 17ß-oestradiol, and the human hormone receptors can therefore mistake them for hormones. The researchers were unable to corroborate their suspicion in experiments because no tests on the bottles themselves had been conducted, and on the basis of the available results, conclusions as to the material were possible only to a very limited extent.
Still, voicing the suspicion was enough to cause outright panic: numerous media articles and NGO mailings warned against the use of PET bottles, neglecting to mention the fact that their warnings were based on mere assumptions, as no analyses on the bottles themselves were available. The study did mention some other potential sources as well, such as disinfectant residues, or contaminated spring water, which, however, was ignored in the media coverage. It was a difficult situation for the beverages industry, particularly manufacturers of PET bottles. It was impossible at that time to test the bottles directly in order to put an end to speculation as no reliable methods of analysis had yet been developed.
The traditional chemical analyses are reliable and very precise as far as the detection of known hormonally active substances such as bisphenol A and phthalates is concerned, but they do not cover hormonally active substances that are still unknown. For the majority of substances that can migrate from the PET bottle into the filling substance, no data on possible hormonal activity are available. The existing chemical screening procedures could thus not contribute to refuting the allegations made.