Triclosan

Toxic and a suspected endocrine disrupter that can mimic or interfere with the function of hormones. The European Union classifies triclosan as irritating to the skin and eyes, and as very toxic to aquatic organisms, noting that it may cause long-term adverse effects in the aquatic environment. Triclosan can also react in the environment to form dioxins, which bioaccumulate and are toxic. Triclosan is an anti-microbial agent and there is concern that its extensive use in consumer products is contributing to antibiotic-resistant bacteria, thus limiting treatment options for microbial infections. The Canadian Medical Association has called for a ban on antibacterial consumer products.

Found in: dish soaps and disinfectants, as well as a wide range of other household products. Look for it listed as an "active ingredient" in antibacterial products.