Plastic link to birth flaws

A common ingredient of plastic used for food containers, including babies' bottles, causes birth defects in mice - defects that could also occur in people.

US researchers have urged more research into the potential effects of bisphenol A, a chemical long criticised by environmentalists as being a hormone disruptor that could cause defects in embryos.

If the defects found in the mice occur in humans, they can cause miscarriages or mental retardation such as Down Syndrome.

And they seem to be caused at what were considered to be low levels of exposure, the researchers report in the journal Current Biology.

The discovery was made by accident, Geneticist Patricia Hunt and colleagues at Case Western Reserve University in Ohio report.

Her team noted a higher than normal increase in abnormalities in developing egg cells in female mice.

"We were looking at the processes as cells start to undergo division," Ms Hunt said.

"The chromosomes are supposed to line up in an orderly fashion so they can divide in an orderly fashion.

"What we saw was a tremendous increase in the number of cells in which the alignment of chromosomes in the cells were not orderly at all."

In the mice they were studying this usually happened 2 per cent of the time, but Ms Hunt's team found 40 per cent of the eggs were developing these problems.

They spent weeks looking for the cause.

"Nothing turned up. But I noticed that the plastic cages looked kind of the worst for wear," Ms Hunt said.



A harsh detergent used to clean the cages had broken down the plastic, releasing bisphenol A.

The team briefly exposed mice to small amounts of bisphenol A and found the abnormalities increased again.

Many labs are studying the effects of bisphenol A and other chemicals that act as endocrine disruptors, affecting the actions of hormones in the body.

Some scientists believe developing foetuses and young children are especially vulnerable to these effects.

"Pat Hunt hasn't shown damage in foetuses yet, but it has to be a subject of concern," said Fred vom Saal, an expert on the effects of toxins on reproduction at the University of Missouri.

"Bisphenol A is one of the most commonly used plastic materials in food containers, in beverage containers.

"This is a ubiquitous chemical ... at least in the developed world."

Ms Hunt, who studies the effects of ageing on egg cells and fertility, said she had not been looking for chemical influences when the discovery was made.

"That's one of the things that makes our study unusual," she said.



The study says nothing about the effects of bisphenol A in humans, but Ms Hunt said there was reason to believe they would be similar to the changes in the mice.

These changes cause aneuploidy - a misalignment of the chromosomes that is seen in human birth defects and miscarriages.

"You don't wait to prove that it does that in people before you take some regulatory action," Dr Vom Saal said.

He hoped the US Congress might agree to finance more studies on the effects of bisphenol A.

"We are talking about these mice essentially drinking out of old baby bottles."

He said hard plastic containers such as bottles start leaching bisphenol A when they begin to look cracked or etched.

He urged the chemical industry to make more plastic products that do not contain bisphenol A.

The problem

* Bisphenol A is one of the most commonly used plastics in food containers, especially beverage containers such as babies' bottles

* Environmentalists have long believed it is a "hormone disruptor" that could cause defects in embryos

* US researchers have found that bisphenol A causes birth defects in mice

* The defects they found, when they occur in humans, can cause miscarriages or mental retardation such as Down Syndrome

- REUTERS