The compounds end up in sewage sludge that is spread on farm fields
across the country.
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
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
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
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.