A research project in conjunction with the German Environment Ministry showed that some were as contaminated as water from sewage works for the oestrogen-like substances.
Martin Wagner, who worked on the study, said in a statement, “When we started the work we did not expect to find such a massive oestrogen contamination in a foodstuff which is so strictly controlled.”
The scientists examined 20 different brands of mineral waters, 12 of which displayed heightened hormone content.
The study, which will be published in the Environmental Science and Pollution Research journal showed that those waters in PET plastic bottles had around twice as much oestrogen contamination as those in glass bottles.
It is thought that the plastic ingredient bisphenol A, which acts like oestrogen, leaches out of the plastic bottles.
“In real life we are not dealing with a single chemical, but with many environmental hormones,” said Professor Jörg Oehlmann, who led the study.
In order to investigate this cocktail effect, the scientists used a genetically-modified strain of yeast which contained human oestrogen receptors.
It is not yet known whether the mineral water contamination could present a health risk.
“Our results show that we are coming into contact with a greater level of environmental hormones than we had previously thought,” Oehlmann. “But we do not yet know anything about their absorption or excretion in and out of the human body.”
It is also not yet known exactly which substance is responsible for the hormonal contamination of the water – the Frankfurt team is continuing to work on this.