Formation of chloroform and other chlorinated byproducts by chlorination of triclosan-containing antibacterial products

Triclosan is a widely used antibacterial agent found in many personal hygiene products. Although it has previously been established that pure triclosan and free chlorine readily react, interactions between triclosan-containing consumer products and free chlorine have not previously been analyzed in great depth. Sixteen double-blinded solutions including both triclosan-containing (1.14-3.12 mg triclosan/g product) and triclosan-free products were contacted with free chlorine at pH 7. Products detected included (chlorophenoxy) phenols, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and chloroform. The daughter product yields were found to be highly variable and were dependent on the antimicrobial product investigated, the free chlorine to triclosan ratio, and the temperature at which the study was conducted. Lowering the temperature from 40 to 30 degrees C resulted in a decreased average chloroform yield from 0.50 to 0.37 mol chloroform/mol triclosan consumed after 1 min of reaction time for an initial free chlorine concentration of 4.0 mg/L as Cl-2. At 40 degrees C the average molar chloroform yields decreased to 0.29 and < 0.1 when the initial free chlorine concentration was decreased to either 2.0 or 1.0 mg/L as Cl-2, respectively. Field experiments, in which Atlanta, GA and Danville, VA tap waters were augmented with various soap products, exhibited results varying from the laboratory experiments in that different product yields were observed. These differences are attributed to the chlorine demand of constituents in the tap water. A simple exposure model suggests that exposure to chloroform can be significant under some conditions.