The Food and Drug Administration announced April 8 that it will be taking a look at the safety of a widely used antibacterial chemical, triclosan.

Triclosan — as well as its cousin triclocarban — is found in liquid hand soaps, deodorant bar soaps, face washes, deodorants, toothpastes and mouthwashes, and as well as in germ-fighting cutting boards and socks. In January, Rep. Edward J. Markey (D-Mass.) wrote letters to the FDA and the U.S. Environmental Protection Agency, urging them to review new evidence about the potential harms of triclosan. Markey has called for banning the chemical in personal care products, citing concerns that widespread use of triclosan may encourage the spread of antibiotic-resistant bacteria and, as it gets washed down millions of household drains, may harm wildlife.

Meanwhile, industry groups such as the Soap and Detergent Assn. and the Personal Care Products Council assert that they have provided volumes of information on the benefits and safety of antimicrobial products.

In a consumer fact sheet, the FDA says that, at present, triclosan is not known to be hazardous to humans. Still, the agency first proposed regulating the chemical for consumer use in the 1970s and has revisited the issue several times since. In a letter responding to Markey, the agency promised to evaluate the new evidence and come to some conclusion by next spring.

Here’s a closer look at what’s known about the benefits and potential harms of triclosan.

Triclosan stops or slows the growth of bacteria and fungi. It is added to many products as a preservative to prevent bacterial contamination within the product itself, but it’s added to soap to help battle germy hands.

Antibacterial soaps do fight germs on your hands — but that’s thanks to the soap, not the triclosan, according to a number of studies.

Allison Aiello, an epidemiologist at the University of Michigan School of Public Health in Ann Arbor, reviewed handwashing studies that directly compared plain soap with antibacterial soap for the journal Clinical Infectious Diseases in 2007. Researchers measured how many bacteria were present after washing — either bacteria planted on subjects’ hands or occurring naturally. Of four studies that tested consumer-strength antibacterial soap, which contains 0.2% to 0.3% triclosan, the only instance in which it bettered plain soap was in subjects who washed their hands 18 times a day for five days in a row.

Aiello also reviewed studies that looked at the rate of infectious illness that occurs in households using antibacterial soap versus plain soap and found no difference. One reason may be that the most common illnesses, such as colds and stomach flu, are viral. Triclosan doesn’t target viruses.

Other studies did sometimes, but not always, find improved germ removal after use of stronger preparations containing 1% triclosan or more, the kind of soap used in hospitals and other healthcare settings.

The hospitals of UCLA use soap with 3% triclosan, but only in patient-care areas and only as an amendment to alcohol-based hand gels, which work faster than washing with soap and have a sustained germ-squashing effect, says Dr. David Pegues, who directs the program on infectious diseases. “I think the use is appropriate in the hospital where we’ve got antibiotic-resistant germs that need to get killed on skin and skin surfaces,” he says. “Where it’s not appropriate is the routine use of a variety of consumer products, mostly for peace of … mind.”

The FDA agrees that triclosan offers no advantage to germ control over regular soap in most settings. However, triclosan-containing toothpaste — such as Colgate Total, which is FDA-approved and recommended by the American Dental Assn. —- does seem to prevent gingivitis better than regular toothpaste.

There’s no question that exposure to triclosan is widespread in the U.S. A national health survey found triclosan in the urine of 75% of the 2,517 people who gave samples. The chemical can enter the body via absorption through the skin or the lining of the mouth.

Mae Wu, a program attorney at the National Resources Defense Council, an environmental advocacy group in Washington, D.C., says that even people who deliberately try to avoid antimicrobial products still end up getting exposed because the soaps are in public restrooms, offices and restaurants.

What triclosan does once it enters the body is not clear. Research in animals has found hormonal effects of triclosan, including upsetting the normal balance of thyroid hormones, thereby impairing growth and brain development, and of the reproductive hormones estrogen and testosterone, leading to infertility. These effects are similar to other so-called endocrine disruptors, such as bisphenol A, dioxins and pesticides such as DDT. The FDA says it intends to evaluate this new research.

Although there are no data on effects of triclosan on human hormone systems, endocrine disruptors as a class are known to have effects at very low levels of exposure, according to the National Institute of Environmental Health Sciences. “It doesn’t take very much to swing the system one way or another,” Wu says.

Another concern is that triclosan, used widely and without restraint, may encourage the growth and spread of antibiotic-resistant pathogens. These have become a huge problem around the world with the rise of superbugs that cause life-threatening infections and are very difficult to treat.

Many doctor groups have called for more restraint in using antibiotic drugs in healthcare settings (not to mention in the raising of farm animals) to keep antibiotic resistance in check. Markey and the American Medical Assn. want the FDA to exert the same cautious approach with antimicrobial chemicals in consumer products.

Triclosan gives scientists cause for concern in this regard because it targets growing bacteria in the same way as some antibiotic medicines. Also, laboratory studies have shown that microbes resistant to triclosan also seem to have picked up resistance to other antibiotic drugs at the same time. But it’s not clear to what extent that’s happening on the hands of Americans.

Aiello attempted to study the issue by randomly assigning participants to use plain soap or antibacterial soap for a year and then looking for antibiotic-resistant bugs. “Although we did find some increases in antibiotic-resistant species [on hands of those using the triclosan-containing soap], the differences were not statistically significant,” she says of her results, which were published in the journal Emerging Infectious Disease in 2005. One difficulty was being sure that her triclosan-free group was truly triclosan-free, she says. “Most people out there are using [antimicrobial products] without even knowing it.”

Even though the harms of triclosan are not well established, many doctors, public health officials and environmentalists think that they’re not worth the risk, especially in light of evidence that triclosan in soap products doesn’t seem to add value. “It doesn’t seem like there’s a place for these chemicals in consumer soap at this point,” Aiello says.

health@latimes.com