According to researchers, bisphenol-A (BPA) - a compound used in large quantities in the manufacture of plastic food containers, dental sealants and resins that line food tins - leaches out of products and could be absorbed into the body, reports the Scotsman.
 
Scientists working with animals have earlier demonstrated that BPA is potentially damaging to health.

But the new study is the first to suggest even extremely weak levels of exposure in the womb may be harmful.

A team of US researchers, led by Professor Ana Soto from Tufts University School of Medicine in Boston, Massachusetts, administered tiny doses of BPA to groups of pregnant mice. The mice were treated during the latter half of their pregnancies and for about four days after giving birth. Their offspring were examined when they reached puberty.

One of the most striking 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. It is here that breast tumours typically form.

The second major finding was that animals previously exposed to the higher dose of BPA developed mammary glands that were much more sensitive to oestrogen, which fuels the vast majority of breast tumours in humans.

Reporting their findings in the latest issue of the Journal of Endocrinology, the researchers wrote: "These correlations suggest that perinatal [shortly before or after birth] exposure to BPA in particular, and to oestrogens in general, may increase susceptibility to breast cancer."

Experts believe the findings have alarming implications for human health.

An estimated six billion pounds of BPA is produced each year around the world.

In addition, the scientists observed a significant drop in the number of cells in this region marked out for death. Programmed cell death, or apoptosis, is a natural defence mechanism that weeds out damaged cells that might turn cancerous.

About 40,000 women are diagnosed with breast cancer each year in Britain, and almost 13,000 die from the disease.

A leading reproductive biologist, Professor Frederick vom Saal from the University of Missouri-Columbia in the US, said it could be assumed that every member of the population was "chronically exposed" to BPA.

He added: "This is of tremendous concern, because this is clearly a study that's relevant to human exposure levels to this chemical."