Plastics spoil mouse eggs
Helen Pearson

Food-packaging compound affects reproductive cell division.

A chemical commonly found in plastic food containers harms growing mouse eggs, according to a new study1 - fuelling the debate over the additive's safety.

The compound is called bisphenol A (BPA). It is widely used in see-through bottles and for lining tin cans. Its chemical activity mimics that of the female hormone oestrogen, so some fear that it might damage an unborn baby's growing sex organs.

In the latest study, Patricia Hunt of Case Western Reserve University in Cleveland, Ohio discovered unusual genetic defects in the eggs of her laboratory mice. She traced it to their hard plastic cages, which were leaching BPA.

Even traces - 20 parts per billion in drinking water - altered 8% of eggs, her team found. Normally, only 1% of eggs are defective. Humans are exposed to similar BPA levels, Hunt says, although it is not known if they have the same effect.

In theory, such genetic flaws could cause a higher incidence of miscarriage or of conditions such as Down's syndrome. "You're talking about transmitting profound chromosomal damage to your baby," says PBA researcher Frederick vom Saal of the University of Missouri-Columbia.

Steve Hentges of the American Plastics Council in Arlington, Virginia, counters that it is too early to condemn BPA - because the team have yet to show whether the genetic changes actually affect the mice's ability to reproduce. "We don't know how to interpret this yet," he argues.

Earlier investigations hinted that exposing animals in the womb to levels of BPA similar to those found in the environment upsets their sperm count, prostate and testicular development. Other studies - some commissioned by the plastics industry - have found BPA to be completely safe.

We don't have any reason to believe there's any effect
George Pauli
US Food and Drugs Administration

Hunt has gone a step further in showing that BPA might also harm an egg's DNA; this damage might be inherited by offspring formed from those eggs. She finds that BPA stops chromosomes from dividing up equally before egg cells divide, possibly by interfering with oestrogen's normal activity.

Hunt, vom Saal and others would like to see BPA regulations tightened. Some regulatory bodies are already reviewing the allowable levels: a European Commission's food-safety committee, for example, last year slashed its upper limit for daily intake fivefold.

The US Food and Drug Administration does not have a safety limit for BPA on foodstuffs. "We don't have any reason to believe there's any effect," argues the administration's George Pauli, who is involved in regulating the safety of plastics in food packaging. But the agency keeps tabs on new research, he adds.
References

1. Hunt, P.A. et al. Bisphenol A exposure causes meiotic aneuploidy in the female mouse. Current Biology, 13, 546 - 553, (2003).