Chemicals in food packaging linked to breast cancer

May 30 2005

Chemicals found in some food packaging materials have been shown in a new study to affect the development of breast tissue in mice, which suggests, say scientists, that women exposed to such chemicals, which mimic female hormones, may be at increased risk of breast cancer.

The research team, from Tufts University in Boston, found that the mammary glands of young female mice developed in a way that made them more likely to develop breast cancer and the mice also became sensitised to oestrogen, the natural hormone that advances many breast cancers.

The main focus of the research was on bisphenol A (BPA), a compound used in the manufacture of plastic food containers which is also present in dental sealants and the resins that line food cans.

It is thought that around 2.5 million tonnes of BPA is produced each year worldwide, and research has shown that the chemical escapes from products and may be absorbed at low concentrations into the body.

This new study by Professor Ana Soto and colleagues is the first to suggest that even extremely low levels of exposure to BPA in the womb may be harmful.

Small doses of BPA were given to pregnant mice in doses ranging from 25 to 250 billionths of a gram and were designed to mimic the levels that humans are likely to be exposed to.

The mice were dosed during the latter half of their pregnancies and for about four days after giving birth. Their offspring were examined at 30 days old, which is when they reached puberty.

One of the effects of BPA exposure was a large increase in the number and density of terminal end buds, part of the mammary gland’s milk-producing structure and this is where breast tumours typically form.

Mice that were exposed to the higher dose of BPA developed mammary glands that were much more sensitive to oestrogen and this was shown by the degree to which oestrogen affected the further growth and structure of terminal end buds.

Professor Frederick vom Saal, a biologist from the University of Missouri, Columbia, said that as every member of the population was “chronically exposed” to BPA the study is clearly relevant to human exposure levels to the chemical.

He says that Professor Soto has produced evidence which is consistent with a number of other reports, that the mammary gland is being altered in its response to sex hormones and the chemical is not only structurally altering the organ, but is permanently changing the function, which is of 'huge public concern'.

The study is published in the journal Endocrinology.