The US Food and Drug Administration in December said it planned more research into the safety of bisphenol A, or BPA, but the agency indicated no immediate plans to curb the chemical, found in baby bottles and other products.

Dr Richard Stahlhut of the University of Rochester and colleagues looked at levels of the chemical in the urine of 1,469 US adults who took part in a government health survey.

While the belief had been BPA was quickly and completely eliminated from the body through urine, this study found people who had fasted for even a whole day still had significant levels of the chemical.

Stahlhut said this suggested BPA may hang around in the body longer than previously known or that it may get into the body through sources other than just food, perhaps including tap water or house dust. Stahlhut added that BPA may get into fat tissue, from where it might be released more slowly.

"If it leaves the body quickly, then it reduces the amount of time when it can cause problems. If it does cause problems, obviously if it stays around much longer, then that changes the game," Stahlhut, whose study appears in the Environmental Health Perspectives journal, said in a telephone interview.

BPA is used in many food and beverage containers, the coating of food cans and some medical devices. It mimics the hormone oestrogen in the body. People consume it when it leaches from plastic into baby formula, water or food in a container.

The researchers tracked how urine levels of BPA declined based on the length of time a person had fasted. But they found that people who fasted for 8.5 hours, for example, had about the same BPA levels as those who fasted 24 hours.

Steven Hentges of the American Chemistry Council industry group said the conclusions of the new study "are speculative at best," and reiterated the industry view that BPA is safe at current levels of exposure.

US government toxicologists at the National Institutes of Health last year expressed concern that BPA may have harmful effects on the development of the prostate and brain and induce behavioural changes in foetuses, infants and children.