Triclosan, a synthetic antibacterial agent, is found in thousands of consumer products, including soaps, cosmetics, acne creams and some brands of toothpaste.
The US Food and Drug Administration (FDA) is reviewing its safety based on a growing body of research indicating that it can interfere with the action of hormones, potentially causing developmental problems in foetuses and newborns, among other health concerns.
In the current study, researchers analysed urine samples from two groups of 38 doctors and nurses - three fourths of them women - at two hospitals, identified as Hospital 1 and Hospital 2.
Hospital 1 used an antibacterial soap containing 0.3 per cent triclosan, while Hospital 2 used plain soap and water.
Workers at Hospital 1 had significantly higher levels of triclosan in their urine than workers at Hospital 2.
The scientists also asked the study participants if they used a popular commercial toothpaste containing triclosan.
While those who did had higher triclosan levels than those who did not, the researchers found that washing with antibacterial soap accounted for even higher triclosan levels than did brushing with the toothpaste.
"Antimicrobial soaps can carry unknown risks, and triclosan is of particular concern," said co-investigator Paul Blanc, a professor of medicine at University of California, San Francisco (UCSF).
"Our study shows that people absorb this chemical at work and at home, depending on the products that they use," said Blanc.
"If non-triclosan-containing soaps are available, use the alternative. This is based on the precautionary principle - that is, if you don't know for certain that something is unsafe, it's better to err on the side of caution," Blanc said.
The study was published in the Journal of Occupational and Environmental Medicine.