title: Development of a 4-NQO toxic equivalency factor (TEF) approach to enable a preliminary risk assessment of unknown genotoxic compounds detected by the Ames II test in UV/H₂O₂ water treatment samples.
abstract: An approach to enable a preliminary risk assessment of unknown genotoxic compounds formed by MP UV/H2O2 treatment of nitrate rich water, is described. Since the identity and concentration of specific genotoxic compounds is not established yet, a compound specific risk assessment cannot be performed. This limitation is circumvented by introducing a toxic equivalency factor, converting the concentration of unknown genotoxic compounds expressed by an Ames II test response into equivalent concentrations of 4-nitroquinoline oxide (4-NQO), to enable a preliminary risk assessment. Based on the obtained 4-NQO equivalent concentrations for the tested water samples and 4-NQO carcinogenicity data, an indication of the associated risk of the by MP UV/H2O2 treatment produced nitrated genotoxic compounds is obtained via the margin of exposure (MOE) approach. Based on a carcinogen study by Tang et al. (2004), a body weight of 70 kg and a drinking water consumption of 2 L per day, the 4-NQO equivalent concentration should not exceed 80 ng/L associated with a negligible risk. Application of this approach on samples from MP UV/H2O2 treated water of a full scale drinking water production facility, a 4-NQO equivalent concentration of 107 ng/L was established. These results indicate a safety concern in case this water would be distributed as drinking water without further post treatment.
authors.affiliation: Wageningen University, Division of Toxicology, P.O. Box 8000, 6700 EA Wageningen, The Netherlands; Wetsus European Centre of Excellence for Sustainable Water Technology, P.O. Box 1113; 8900 CC Leeuwarden, The Netherlands; PWN Water Supply Company North Holland, P.O. Box 2113, 1990 AC Velserbroek, The Netherlands. Electronic address: bmartijn@pwntechnologies.nl.
authors.forename: Bram J
authors.initials: BJ
authors.lastname: Martijn
authors.affiliation: VITO - Environmental Risk & Health - Team ABS, Industriezone Vlasmeer 7, 2400 Mol, Belgium.
authors.forename: An R
authors.initials: AR
authors.lastname: Van Rompay
authors.affiliation: Het Waterlaboratorium, P.O Box 734, 2300 RS Haarlem, The Netherlands.
authors.forename: Eric J M
authors.initials: EJ
authors.lastname: Penders
authors.affiliation: Wageningen University, Division of Toxicology, P.O. Box 8000, 6700 EA Wageningen, The Netherlands.
authors.forename: Yousif
authors.initials: Y
authors.lastname: Alharbi
authors.affiliation: Icastat, Niagara 18, 1186 JP Amstelveen, The Netherlands.
authors.forename: Paul K
authors.initials: PK
authors.lastname: Baggelaar
authors.affiliation: Wetsus European Centre of Excellence for Sustainable Water Technology, P.O. Box 1113; 8900 CC Leeuwarden, The Netherlands.
authors.forename: Joop C
authors.initials: JC
authors.lastname: Kruithof
authors.affiliation: Wageningen University, Division of Toxicology, P.O. Box 8000, 6700 EA Wageningen, The Netherlands.
authors.forename: Ivonne M C M
authors.initials: IM
authors.lastname: Rietjens
mesh_terms: D015112:4-Nitroquinoline-1-oxide / Q000633:toxicity; D000328:Adult; D002273:Carcinogens / Q000737:chemistry / Q000528:radiation effects / Q000633:toxicity; D004249:DNA Damage; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry*; D009152:Mutagenicity Tests; D009566:Nitrates / Q000737:chemistry / Q000528:radiation effects / Q000633:toxicity; D015363:Quinolones / Q000633:toxicity; D018570:Risk Assessment; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000528:radiation effects / Q000633:toxicity; D018508:Water Purification / Q000379:methods*
chemical_list: C120195:4-nitroquinolone-1-oxide; D002273:Carcinogens; D009566:Nitrates; D015363:Quinolones; D014874:Water Pollutants, Chemical; D015112:4-Nitroquinoline-1-oxide; D006861:Hydrogen Peroxide
keywords: 4-NQO; Ames test; Genotoxicity; Margin of exposure; Medium pressure UV; Nitrate photolysis; Nitration