Although the discovery points to a link between breast tumours and the chemical group called parabens - common in shampoos, foundations, facial masks, hair-grooming aids, nail creams and permanent wave products - it is not clear exactly what the relationship is.
Previous animal and laboratory studies have shown that parabens can mimic the actions of the cancer fueling hormone estrogen. However the latest report published in the Journal of Applied Toxicology takes things one step further.
"We have always been assured that parabens could not get into the body, this study shows that they do. It's one more nail in the coffin, or one more piece in the jigsaw," said author of the study Philippa Darbre.
A 1984 study estimated parabens were used in 13,200 different cosmetic formulations. Of particular concern are underarm products, such as deodorants and antiperspirants, which are applied topically and absorbed through the skin.
Darbre, a senior lecturer in oncology at the University of Reading in the UK, analysed samples of 20 human breast tumours with high-pressure liquid chromatography followed by tandem mass spectrometry.
In four of the 20 tumours, total paraben concentration was more than twice the average level. The researchers claim that the form the chemicals were found in suggests they entered the body topically and not orally.
The study authors acknowledge that many issues need to be resolved before any definitive conclusions can be reached.