Besides the possibility of prolonged triclosan exposure, the study findings suggest that triclosan could find its way into the environment if tainted toothbrushes are discarded, the researchers said in a news release from the American Chemical Society.

The U.S. Food and Drug Administration banned triclosan from antiseptic washes because of possible harmful effects and because there was no proof they killed germs more effectively than soap and water. The chemical is still allowed in clothing and cookware, which don't fall under the FDA.