Saturday, May 13, 2006
Threat Seen From Antibacterial Soap Chemicals
by Marla Cone
Tons of chemicals in antibacterial soaps used in the bathrooms and kitchens of virtually every home are being released into the environment, yet no government agency is monitoring or regulating them in water supplies or food.
About 75% of a potent bacteria-killing chemical that people flush down their drains survives treatment at sewage plants, and most of that ends up in sludge spread on farm fields, according to Johns Hopkins University research. Every year, it says, an estimated 200 tons of two compounds — triclocarban and triclosan — are applied to agricultural lands nationwide.
The findings, in a study published last week in Environmental Science & Technology, add to the growing concerns of many scientists that the Environmental Protection Agency needs to address thousands of pharmaceuticals and consumer product chemicals that wind up in the environment when they are flushed into sewers.
From dishwashing soaps to cutting boards, about 1,500 new antibacterial consumer products containing the two chemicals have been introduced into the marketplace since 2000. Some experts worry that widespread use of such products may be helping turn some dangerous germs into "superbugs" resistant to antibiotics.
Triclocarban, an ingredient of antibacterial bar soaps and toothpaste, is "potentially problematic" because it breaks down slowly, which means it is accumulating in soil and perhaps water, said Rolf Halden, an assistant professor at Johns Hopkins' Department of Environmental Health Sciences, who led the study.
"What we are finding is this chemical is building up in the environment," Halden said. "This is an example of an emerging contaminant. It has been in the environment for almost five decades, and we manufacture large volumes of it, but we don't know what happens to it."
The scientists calculated that a large, modern East Coast sewage treatment plant spreads sludge containing more than 1 ton of triclocarban onto farm fields every year. The plant was not identified by the researchers, but data in the study indicated that it was in Baltimore.
Southern California's sludge has not been analyzed for antibacterial chemicals. But households in the Los Angeles region are likely to be a major source, because sewage plants in the area produce hundreds of thousands of tons of sludge every year.
Sludge is the solid waste that is left when sewage is processed in treatment plants. Billions of pounds are produced annually in the United States — 47 pounds per person — and two-thirds is hauled to agricultural fields for disposal. Federal regulations limit metals and pathogens in sludge, but not other chemicals.
Triclocarban is used in bar soaps, deodorants, toothpaste, kitchen supplies such as cutting boards and countertops, and baby toys. Triclosan, which is more abundant because it is used in liquid soaps, has been detected in human breast milk and fish in streams in Europe.
Toxicological tests have shown that the chemicals seem safe for human exposure, even in the high doses applied to skin. However, in water, triclosan can react with chlorine and turn into chloroform and dioxins linked to cancer. The chemicals also might kill microbes beneficial to ecosystems or promote new pathogens that resist antibiotics.
Allison E. Aiello, an assistant professor of epidemiology at the University of Michigan's School of Public Health who has studied antibacterial soaps, calls the new report an important finding that "suggests these types of chemicals are persistent and prevalent in the environment."
"From these findings, it seems likely that microorganisms in the environment are often exposed to these chemicals at various concentrations," Aiello said. The next step, she said, is to assess whether these microbes show reduced resistance to antibiotics.
Previous research by Halden suggested that triclocarban was among the top 10 contaminants in waterways, while triclosan was among the most prevalent in a national analysis of streams by the U.S. Geological Survey.
Yet no one knows whether the chemicals are contaminating crops or groundwater. Drinking water also is not monitored for them. The EPA is exploring the prevalence of pharmaceuticals and personal care products in the environment, but it has nowhere near enough data to consider regulations for sludge.
Rick Stevens, national biosolids coordinator at the EPA's Office of Science and Technology, said the discovery of triclocarban in the plant's sludge was "of interest" to the EPA, but "at this time, the agency cannot determine what significance [the concentrations found] may represent to humans or the environment due to the limitations in the database."
Stevens said there were no national data — not even an accepted, standardized technique for measuring the chemicals. "One facility is not a nationally representative sample," he said.
Triclocarban in the plant's sludge averaged 51 parts per million, considered a high concentration for an environmental contaminant. But Stevens said people regularly rubbed triclocarban into their hands at levels 100 times higher. Also, the chemicals would be degraded and diluted on farm fields, he said.
Hans Sanderson, director of environmental safety at the Soap and Detergent Assn., which represents manufacturers, said the new research was "important and analytically sound" and was helping address what happens to the chemicals in soaps and other household products.
But Sanderson said it was wrong to assume that the presence of them in the sludge meant that they were posing risks. Most sludge is applied to fields and forests that do not produce food crops, he said.
"It is clear that the majority of exposure to triclocarban is direct exposure, when you actually use these materials in hand soap or toothpaste or whatever," Sanderson said. But, he said, laboratory tests have shown that even those exposures have no effects on animals, are not toxic to aquatic life and pose no known threat to people.
Ann Heil, a senior engineer at the Sanitation Districts of Los Angeles County, said many environmental precautions were required on lands where sludge was applied. The material is plowed into soil within 24 hours and no runoff is allowed.
Heil said it probably was better that treatment plants removed the antibacterial chemicals from wastewater and concentrated them in the sludge, because otherwise the chemicals would be discharged into streams where they could harm wildlife.
Farm disposal of sludge is controversial in California. On June 6, residents of Kern County, which takes in one-third of the state's sludge, will vote on whether to ban its use on farms. If the measure passes, as expected, Southern California will have to ship more sludge to Arizona at an extra cost of millions of dollars a year in Los Angeles alone.
About 37% of the 160,000 tons produced last year by the Sanitation Districts of Los Angeles County was applied on land. The county's sludge is subjected to an extra process called thermal treatment, which Heil said probably removed more antibacterial chemicals than the East Coast plant studied in the report.
But, Halden said, even newer tests, yet to be published, showed that the heat treatment was "not very effective" in eliminating antibacterial chemicals. So this "Type A" sludge, the type used on food crops, still could contain high amounts.
In October, an advisory panel of the Food and Drug Administration reported that there was no evidence that the household products protected people any better than regular soap. The panel urged the agency to study their risks and benefits. The American Medical Assn. has opposed routine use of antibacterial soaps since 2002.
"The bottom line," Halden said, "is [that] we are mass-producing chemicals in the environment that are not helpful and potentially are harmful."
But Sanderson of the Soap and Detergent Assn. said it would be foolish to eliminate products that could stem the spread of diseases when there was no evidence they posed a threat.