May 29, 2008 -- Millions of Americans use antibacterial soaps and household cleaners every day, believing that their germ-killing ability will keep them and their families healthier.
But could these same chemicals that fight germs also be hazardous to your health?
That's a question being studied by a group of researchers at the University of California, Davis. In three separate studies, the researchers showed that the chemicals -- triclosan and triclocarban -- have potential to affect sex hormones and interfere with the nervous system.
They also may become suspects in the search for causes of autism.
Dan Chang, PhD, a professor of environmental engineering at U.C. Davis and one of the researchers involved, says he doesn't want to cause a panic, but "the public should be aware of some of the concerns."
While Chang and the other researchers involved in the studies admit that it's too early to know whether the chemicals pose a serious health risk, it's already been shown that the cleaners might not work any better than regular soap and water -- and may contribute to the rise of resistant bacteria. So, they ask, why take the risk?
In October, the researchers will pose that question when they meet with representatives of the Environmental Protection Agency (EPA), the CDC, and some of the product manufacturers to talk about what they view as a potential public health problem.
The stakes are high for the manufacturers: Antibacterial products account for about $1 billion in sales annually. Triclosan is found in 76% of all liquid soap sold in stores and is also added to toothpaste, mouthwash, cosmetics, fabrics, and plastic kitchenware. Triclocarban is a common additive in antibacterial bar soap and deodorant.
"These compounds should be voluntarily removed by consumer product manufacturers," Chang tells WebMD, or at least, consumers should "be provided precautionary information regarding their use."
Brian Sansoni, spokesman for the Soap and Detergent Association, an organization headquartered in Washington D.C. that represents manufacturers of all kinds of cleaning products, says studies have shown the products are safe.
"They have been reviewed and analyzed and studied by scientists and government agencies for decades," Sansoni says. "We're disappointed at some of the alarmist conclusions made by the authors."
Sansoni confirms that a representative of the association plans to meet with U.C. Davis researchers. But he says their findings aren't too worrisome.
"Consumers can continue to safely use antibacterial soap and hygiene products with confidence," he says.
The Government's Perspective
Developed in the 1950s and 1960s, triclocarban and triclosan were first used mainly as antiseptic agents in hospitals. Sales of consumer antibacterial products took off in the early 1990s, backed by multimillion-dollar ad campaigns for popular soap. By 2004, manufacturers were introducing hundreds of new antibacterial products every year.
The EPA is in the process of re-evaluating triclosan. A draft report published in the Federal Register in May 2008 concludes that it doesn't pose any serious safety concerns for consumers. The European Commission reached the same conclusions about triclosan in 2002 and triclocarban in 2005.
The data on toxic effects cited in these reports primarily come from animal studies dating back to the 1970s and 1980s, which were not designed to detect the same kinds of effects that the U.C. Davis researchers are now studying in the lab and in animals.
"The science itself I think is quite good," says Kevin Crofton, PhD, a neurotoxicologist with the EPA's National Health and Environmental Effects Research Laboratory, when asked about the U.C. Davis research. "The conclusions are where it gets hard. They're pointing out something that's new. Does it require further study? Absolutely. But the thing that I think you have to keep in mind is that what we don't really know is the relationship between human exposures and the exposures in those studies."
The effects seen in the laboratory may not necessarily occur in people. "We need to follow that up," Crofton says.
What the Reseachers Found: Triclosan
Chang, who coordinates the university's studies on triclosan and triclocarban as part of the Superfund Basic Research Program, supported by the National Institute of Environmental Health, says the U.C. Davis research doesn't contradict findings that triclosan and triclocarban are safe for most people.
But it does show that "there may be sensitive periods in development when these compounds could have a very subtle detrimental effect." Translation: If the compounds cause harm, they are most likely to do so during pregnancy, early childhood, and adolescence.
Chang argues that antibacterial soaps don't do enough good to risk this potential harm.
In 2005, an FDA advisory panel concluded that antibacterial soaps, as used by the general public, don't prevent illness any better than ordinary soap, and they may contribute to the rise of resistant bacteria.
In one study, recently accepted for publication in the journal Environmental Health Perspectives and made available online, Isaac Pessah, PhD, director of the U.C. Davis Children's Center for Environmental Health, looked at how triclosan may affect the brain.
Pessah's test-tube study found that the chemical attached itself to special "receptor" molecules on the surface of cells. This raises calcium levels inside the cell. Cells overloaded with calcium get overexcited. In the brain, these overexcited cells may burn out neural circuits, which could lead to an imbalance that affects mental development.
Some people may carry a mutated gene that makes it easier for triclosan to attach to their cells. That could make them more vulnerable to any effects triclosan may cause.
This is one reason why Pessah named triclosan (and related compounds with similar properties) as a prime target for research into environmental factors that might cause autism.
"These are the compounds you should be going after," he said last April at the Current Trends in Autism conference held in Boston.
While Pessah's new study does not link triclosan directly to autism, many scientists suspect that having certain genes, plus exposure to something in the environment, might trigger processes that lead to autism.
"We already have a list of candidate genes," Pessah says These are genes commonly found in people with autism that may increase vulnerability to things that impact excitable brain cells.
What the Researchers Found: Triclocarban
Other researchers at U.C. Davis found that the other chemical under study, triclocarban, has an unusual effect on hormones. Triclocarban is a common additive in antibacterial bar soap and deodorant.
For many years, some scientists have suspected that chemicals in the environment, known as "endocrine disruptors," may interfere with the human sex hormones and reproductive development.
According to the National Institute of Environmental Health Sciences, endocrine disruptors may cause reduced fertility in women and men, early puberty in girls, and increases in cancers of the breast, ovaries, and prostate.
In the March 2008 issue of Endocrinology, the researchers published results of studies in animals showing that triclocarban appears to amplify the effects of hormones, telling cells to keep doing something after they normally would have stopped.
In a separate test published in the Endocrinology study, the prostate glands of rats exposed to triclocarban and testosterone grew bigger than those given testosterone alone.
Such studies cannot be repeated in humans for ethical reasons, so researchers must infer that triclocarban could have the same effect in humans.
Lathering up for a single bath with soap containing triclocarban gives a person the same dose of triclocarban that rats got in the study.
"We do know that people, after a shower, or after an acute exposure, can have levels that could have an effect on their hormones," says Bill Lasley, PhD, a researcher in the department of population health and reproduction at U.C. Davis. "I have no doubt that it has a subtle effect, but I of course question whether it has a serious effect."
Chemical Buildup in Environment
The U.C. Davis researchers are the first to use cutting-edge molecular technology to study potential effects of triclosan and triclocarban on the human nervous system and hormones. Studies show that these chemicals are building up in the environment at an alarming rate.
Americans dump more than 1 million pounds of triclosan and triclocarban into the environment every year. Rolf Halden, PhD, a scientist at Arizona State University, found that sewage treatment captures only about 50% of the triclosan and less than 25% of the triclocarban that goes down people's drains.
Halden published a study this month in Environmental Science and Technology showing that the chemicals don't quickly break down in the environment. He found these chemicals in sediment dating back 40-50 years.
A recent CDC study detected triclosan in the urine of 75% of Americans aged 6 and older.
"The disappointing news is that we continue to use these chemicals against better knowledge," Halden says. "They do not have an observable benefit. But we do know they persist in the environment, and now these more recent studies show that they are not as benign as we might have thought."
Antonia Calafat, PhD, a laboratory scientist at the CDC, says the agency does not know if any health problems in the population are linked to triclosan exposure. "We need additional research to determine whether or not, at the levels we have detected, triclosan can be a cause of concern," she says.