Comparison of DNA damage in human-derived hepatoma line (HepG2) exposed to the fifteen drinking water disinfection byproducts using the single cell gel electrophoresis assay

Abstract

Disinfection of drinking water reduces pathogenic infection, but generates disinfection by-products (DBPs) in drinking water. In this study, the effect of fifteen DBPs on DNA damage in human-derived hepatoma line (HepG2) was investigated by the single cell gel electrophoresis (SCGE) assay. These fifteen DBPs are: four trihalomethanes (THMs), six haloacetic acides (HAAs), three haloacetonitriles (HANs), 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), and chloral hydrate (CH). Based on the minimal effective concentration (MEC) at which DBPs induced significant increase in olive tail moment (OTM), the rank order of DNA-damaging potency is: bromodichloromethane (BDCM) > dibromochloromethane (DBCM) > tribromomethane (TBM) > trichloromethane (TCM) of the four THMs; iodoacetic acid (IA) > bromoacetic acid (BA) > dibromoacetic acid (DBA) > dichloracetic acid (DCA) > trichloroacetic acid (TCA) of the five HAAs; dibromoacetonitrile (DBN) ≈ dichloroacetonitrile (DCN) > trichloroacetonitrile (TCN) of the three HANs. The DNA damaging potency of MX and CH is similar to TCA and DCA, respectively. IA is the most genotoxic DBP in the fifteen DBPs, followed by BA. Chloroacetic acid (CA) is not genotoxic in this assay. Our findings indicated that HepG2/SCGE is a sensitive tool to evaluate the genotoxicity of DBPs and iodinated DBPs are more genotoxic than brominated DBPs, but chlorinated DBPs are less genotoxic than brominated DBPs.