Antimicrobial Soaps: Worth the Risk?

Soaps with biocides may be harmful to human health and the environment.

Chemicals found in antibacterial soaps and other “germ-fighting” household products may pose greater health and environmental risks than we suspect, according to Rolf Halden, co-founder of the Johns Hopkins University Center for Water and Health. Dr. Halden made the comments at a conference on the risks and benefits of antimicrobial products last week in Washington, D.C., noting that frequent hand washing with plain soap, which is naturally “antimicrobial,” can be just as effective for maintaining public health. Brian Sansoni, vice president of communication at the Soap and Detergent Association (SDA), defended the antimicrobial cleansers.

The controversy surrounds the common addition of two chemical compounds—triclocarban (TCC) and triclosan (TCS)—in soaps, detergents, and other personal care products. In April, Halden and his colleagues released a study showing that while wastewater treatment removes 97 percent of TCC from municipal sewage, as much as 75 percent of the mass of the chemicals is then transferred to the sewage sludge. When the sludge is recycled for use on agricultural lands, the TCC enters the soil and can potentially contaminate adjacent surface waters. In other words, Halden explained, when a consumer buys four bars of antiseptic soap, the “active” ingredient of as many as three of them will make its way into agriculture.

The presence of TCC in soil and water supplies is of concern because the chemical degrades into two substances, both of which are carcinogens, Halden explained. TCS, meanwhile, is a precursor of environmentally persistent dioxins; during drinking water treatment, it may be converted into known animal and possible human carcinogens, including chloroform. While experts agree that direct application of soaps containing TCC and TCS probably poses little risk to users, if the chemicals and their transformation products are introduced to humans through food and water supplies, this may eventually create health problems. To date, traces of TCS have been discovered in fish and in human breast milk. “Biocides are abundant now in the environment,” Halden noted.

Mr. Sansoni with the SDA, however, defended cleansers containing TCC and TCS, even suggesting that it would be beneficial to increase the chemicals’ use. He cited a 2005 meeting of the Nonprescription Drugs Advisory Committee of the U.S. Food and Drug Administration, where members unanimously agreed on the effectiveness of the two antimicrobials in reducing infection. Halden countered that the same committee agreed 11 to 1 that, when used outside of the healthcare setting, the products have not been demonstrated to be more effective than soap. Sansoni said he believes the products can be particularly important for people who work with populations at high risk for infection, such as children and the elderly.

Sansoni also said he did not believe the products pose environmental risks to water and soil, citing a 1975 study that found the chemicals to be “inherently biodegradable.” But Halden responded that more modern research is needed to explore this claim, and that his own studies have found that the chemicals degrade particularly slowly in wastewater treatment and in aquatic sediments.

Another common concern is that the overuse of antimicrobial products can contribute to antibiotic resistance by encouraging the emergence of so-called “super-germs.” Sansoni quoted an industry report saying that, “there is no evidence in real-world situations outside the lab that antimicrobials can select for antibiotic-resistant bacteria.” Halden acknowledges this perspective but also points out that in general, “co-occurrence of bacteria and antimicrobials at high concentrations is known to breed resistance.” Until more conclusive studies are completed, Halden promotes caution in TCC and TCS use in non-healthcare settings.

This story was produced by Eye on Earth, a joint project of the Worldwatch Institute and the blue moon fund. View the complete archive of Eye on Earth stories, or contact Staff Writer Alana Herro at aherro [AT] worldwatch [DOT] org with your questions, comments, and story ideas.