It's a chemical that's been in U.S. households for more than 40 years, from the body wash in your bathroom shower to the knives on your kitchen counter and the bedding in your baby's basinet.
But federal health regulators are just now deciding whether triclosan - the germ-killing ingredient found in an estimated 75 percent of antibacterial liquid soaps and body washes sold in the United States - is ineffective or, worse, harmful.
The Food and Drug Administration is planning to deliver a review this year of whether triclosan is safe. The ruling could have implications for a $1 billion industry that includes hundreds of antibacterial products.
The review comes amid growing pressure from lawmakers, consumer advocates, and others. Recent studies of triclosan in animals have led scientists to worry that it could increase the risk of infertility, early puberty, and other hormone-related problems in humans.
"To me, it looks like the risks outweigh any benefit associated with these products right now," said Allison Aiello, professor at the University of Michigan's School of Public Health.
Many chemicals used in household products have never been formally approved by health regulators. That's because many germ-killing chemicals were developed decades ago, before there were laws requiring scientific review of cleaning ingredients.
The controversy also highlights how long it can take the federal government to review the safety of such chemicals.
In the case of triclosan, Congress passed a law in 1972 requiring that the FDA set guidelines for dozens of common antibacterial chemicals found in over-the-counter soaps and scrubs.
In 1978, the FDA published its first tentative guidelines for chemicals used in liquid hand soaps and washes. The draft stated that triclosan was "not generally recognized as safe and effective," because regulators could not find enough scientific research demonstrating its safety and effectiveness.
The agency published several drafts of the guidelines over the years, but never finalized the results. Then, last summer, the agency said its review would be complete by late 2012, and then February.
"Triclosan is one of the most reviewed and researched ingredients used in consumer and health care products," said Brian Sansoni, a spokesman for the American Cleaning Institute, whose members include Colgate-Palmolive and Henkel Consumer Goods Inc., maker of Dial.