About 76 percent of a commonly used antimicrobial agent exits sewage-treatment plants as a component of the sludge that's often used as a farm fertilizer, according to the first study to track the chemical through a typical plant. The finding raises questions as to the ultimate fate of the antimicrobial in the environment, the study's authors say.
U.S. manufacturers add 500,000 to 1 million pounds of the chemical triclocarban each year to personal-care products, such as antimicrobial soaps. Past toxicological studies have linked the chemical to decreases in birthweight and survival in rats and rabbits, says Rolf U. Halden of Johns Hopkins University in Baltimore.
Halden and his colleagues followed triclocarban through a treatment plant that takes in 680 million liters of wastewater per day produced by 1.3 million residents of a city in the mid-Atlantic region. The plant separates the sewage into liquid and solid streams, and microbes break down much of the organic conte