Triclosan is harmful in many different ways, both to human health and to the environment. It can cause skin irritation, and has been linked to increased susceptibility to allergies. Since triclosan is lipophilic (fat-soluble), it is absorbed into the body and stored in fat cells, where the concentration builds over time. In a CDC study, triclosan was detected in the urine samples of 75% of people tested. Swedish researchers detected triclosan in 3 out of 5 breast milk samples.
When antibacterial personal care and cleaning products are used in the home, the triclosan ends up in wastewater treatment plants. The treatment process removes most, but not all, of the triclosan, and residual amounts are discharged back into the surface water.
If antibacterial soaps are used outdoors, such as for washing vehicles, the runoff containing triclosan goes directly into storm drains and is carried to streams, rivers, and into the ocean. It is toxic to aquatic organisms, particularly algae, and it also bioaccumulates in fish, reaching concentrations thousands of times higher than the amount found in the water.
Triclosan reacts with chlorine in tap water to produce chloroform, a suspected carcinogen. When exposed to sunlight, triclosan photodegrades into a number of highly toxic dioxin-related compounds.
Overuse of antimicrobial agents such as triclosan can promote the growth of antibiotic-resistant bacteria. Rather than simply killing the bacteria by breaking them open, triclosan works by passing into the bacterial cell and interfering with the bacteria's metabolism by inhibiting an enzyme necessary for fatty-acid synthesis. Bacteria become resistant when random mutations generate alternate forms of the enzyme that are unaffected by triclosan, and these resistant bacteria can then multiply and spread.
