Hand WashingThe antibacterial agent triclosan, commonly used in certain soaps, is starting to appear in consumer products ranging from socks to toothpaste.

But research shows that under normal household conditions triclosan can react with chlorinated water to produce chloroform, a likely carcinogen.

An initial 2005 study showed that, in the laboratory, pure triclosan reacts with free chlorine to produce chloroform. More recently, follow-up studies on 16 products found that household goods containing triclosan produced either chloroform or other chlorinated byproducts.

In some soaps, the triclosan degraded within one minute of exposure to chlorinated water at temperatures used for household cleaning.