Study links common plastic to birth defects

By Maggie Fox

WASHINGTON (Reuters) - A common ingredient used to make plastics such as baby bottles causes birth defects in mice -- defects that could also occur in people, U.S. researchers said on Monday.

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

The defects they found, when they occur in humans, 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 came by accident, Patricia Hunt and colleagues at Case Western Reserve University in Ohio report.

Her team first 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," Hunt, a geneticist, said in a telephone interview.

"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 -- they were very disorderly."

In the mice they were studying this only usually happens 2 percent of the time, but Hunt's team said 40 percent 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," Hunt said.

It turned out that a harsh detergent used to clean the cages had broken down the plastic, releasing bisphenol A.

Hunt's team deliberately exposed mice to small amounts of bisphenol A for short periods of time and found the abnormalities increased again.

CHEMICALS THAT DISRUPT HORMONES

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 fear that developing fetuses and young children are especially vulnerable to these effects.

"Pat Hunt hasn't shown damage in fetuses 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. It is one of the top 50 chemicals in production."

Hunt, who studies the effects of aging on egg cells and fertility, said she was not even looking for chemical influences. "That's one of the things I think makes our study unusual," she said.

While the study says nothing about the effects of bisphenol A in humans, Hunt said there is reason to believe they would be similar. The changes in the mice 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," Vom Saal said, adding that he hopes Congress may now agree to fund more studies on the effects of bisphenol A.

"We are talking about these mice essentially drinking out of old baby bottles," Vom Saal said -- noting that hard plastic containers like 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.

Some of the funding for the study came from the industry-supported American Chemistry Council via the National Institute for Environmental Health Sciences.