Trichlorocarbanilide (TCC) is an antibacterial and anti-fungal substance used in soaps and deodorant which has come under new scrutiny by the US Food and Drug Administration for three reasons:

Studies on animals have shown that TCC artificially amplifies sex hormones (estrogen and testosterone), which often leads to breast and prostate cancer. (Animal studies don’t always predict human studies.)
Other studies question whether TCC is one of the ingredients that makes bacteria resistant to antibiotics, encouraging the growth of ‘superbugs’.
Most of these products get washed down the drain and spread through the environment, potentially disrupting aquatic ecosystems.

For some consumer products, TCC provides a legitimate benefit. But for others, the FDA has found no evidence that TCC provides any benefit over plain old soap and water.