Chloramine Fallout In Water Purification

Disinfection by-products (DBPs) are the unintended consequence of chlorinating public water supplies to reduce microbial pathogens. More than 600 DBPs have been identified since 1974, and studies have shown that many of these compounds can be toxic. Last year, an EPA rule aimed at addressing DBPs went into effect, leading water utilities to begin switching from chlorine to chloramines. As it turns out, the DBPs that arise from using chloramines may be the most toxic, according to a study by Michael J. Plewa of the University of Illinois, Urbana-Champaign, and colleagues (Environ. Sci. Technol., DOI: 10.1021/es071754h). The researchers are conducting the first systematic in vitro mammalian cell and gene toxicity analysis of DBPs. For the study, they are analyzing DNA damage to Chinese hamster ovary cells caused by DBPs. By testing 13 haloacetamides, including a newly identified DBP called bromoiodoacetamide, they determined that iodo- and bromoacetamides are more toxic than chloroacetamides (I > Br >> Cl). This pattern corresponds to how easily the halogens are cleaved from the DBPs.