Laboratory mice have suffered genetic damage from a compound used in many household items, US researchers say.
By Alex Kirby
BBC News Online environment correspondent
The compound, bisphenol A (BPA), is used for making some plastics and resins, food packaging, and dental sealants.
The exposed mice showed increases in meiotic errors - the flawed division of reproductive cells.
The researchers believe BPA is a potent meiotic aneugen, a substance that affects the number of chromosomes, the structure into which DNA is bundled.
The team, headed by Dr Patricia Hunt of Case Western Reserve University, describe their work in Current Biology.
They found BPA, a manmade compound which in the body has hormone-like properties that mimic the effects of natural oestrogens, could cause meiotic aneuploidy in female mice.
Meiosis is the division of a cell producing eggs or sperm in which the nucleus splits twice, resulting in four sex cells each possessing half the number of chromosomes of the original cell. It is characteristic of organisms that reproduce sexually.
Aneuploidy is the gain or loss of individual chromosomes from the normal set.
BPA is used in the manufacture of polycarbonate plastics and epoxy resins, in food and drink packaging, often for lining cans, and in dentistry.
Dr Hunt and her colleagues were studying mice in an unconnected piece of research when they noticed a sudden increase in meiotic errors in the animals, including aneuploidy.
Investigations showed this coincided with the inadvertent exposure of the mice to a source of BPA in their laboratory housing, damaged caging material.
The team spent several years checking if this really was the cause by deliberately damaging cages and water bottles, and then giving the female mice daily oral doses of BPA.
They say: "Our results demonstrated that the meiotic effects were dose-dependent and could be induced by environmentally relevant doses of BPA.
"These results provide the first unequivocal link between mammalian meiotic aneuploidy and an accidental environmental exposure.
"We have observed meiotic effects in mice at exposure levels close to or even below those considered 'safe'.
"A recent study of pregnant women and their foetuses conducted in Germany suggests that current human exposure levels may well be within this range.
"The possibility that BPA exposure increases the likelihood of genetically abnormal offspring is too serious to be dismissed without extensive further study."
Ana Soto is professor of cell biology at Tufts University medical school, US. She told BBC News Online: "First, anyone else using similar cages may be producing totally spurious research results.
"Beyond that, this is one more piece of research - and an important one - that adds to the picture we've built up.
"We've already found evidence that BPA can damage the mammary, the uterus and the male genital tract in lab animals.
"This research shows it alters reproductive cells both in foetuses and in adult animals. It's a finding that could be significant for human health."
Reassurance from industry
David Thomas, of the BPA industry group, told BBC News Online: "Some powerful studies have looked for possible effects of BPA, like miscarriages or litter size in animals, and haven't found them.
"We have a high level of confidence these initial studies don't translate into the postulated effects in real animals.
"And we don't think this adds to concerns anyone may have about possible effects of BPA on human health."
Gwynne Lyons, toxics science and policy advisor to WWF UK, told BBC News Online: "It looks as if the smoking gun on bisphenol A is now firing."
Mary Taylor of Friends of the Earth UK said: "This research adds to our concerns about BPA and reinforces our view that it should be phased out and replaced with safer chemicals."