New research suggests that large quantities of a popular ingredient in antibacterial soap could be entering the environment through recycled sewage sludge.
Researchers looking for emerging contaminants in wastewater treatment plants (WWTPs) face a formidable challenge—to “find the needle in the haystack,” says Rolf Halden, an assistant professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health. In a study posted today to ES&T’s Research ASAP website (DOI: 10.1021/es052245n), Halden and his coauthors report that approximately 75% of the mass of a popular antiseptic called triclocarban that enters a typical WWTP persists in the treated sludge.
Researchers sampling sludge
Rolf Halden
Researchers sample sludge in a wastewater treatment plant. They have discovered that a common antiseptic additive, triclocarban, persists in sewage sludge at elevated levels.
Their work is the first peer-reviewed field study of triclocarban in sewage sludge and one of the few reports of the compound’s fate during wastewater treatment. The findings suggest that—given the high rate of sewage sludge reuse as fertilizer—a single WWTP can return more than 1 metric ton of triclocarban to the environment. The authors agree that their findings also raise the question of whether triclocarban could be promoting antibiotic resistance in bacteria in the sludge or elsewhere in the environment.
Triclocarban, commercially known as TCC, is a pesticide used extensively as an antimicrobial additive in soaps and body washes; one survey of commercial products found it in 30% of bar soaps. With annual production estimated at 1 million pounds or more, triclocarban is classified as a high-production-volume chemical by the U.S. EPA."