title: The interaction effects of binary mixtures of benzene and toluene on the developing heart of medaka (Oryzias latipes).
abstract: The United States Environmental Protection Agency (USEPA) has pursued the estimation of risk of adverse health effects from exposure to chemical mixtures since the early 1980s. Methods used to calculate risk estimates of mixtures were often based on single chemical information that required assumptions of dose-addition or response-addition and did not consider possible changes in response due to interaction effects among chemicals. Full factorial designs for laboratory studies can produce interactions information, but these are expensive to perform and may not provide the information needed to evaluate specific environmentally relevant mixtures. In this research, groups of Japanese medaka (Oryzias latipes) embryos were exposed to binary mixtures of benzene and toluene as well as to each of these chemicals alone. Endpoint specific dose-response models were built for the hydrocarbon mixture under an assumption of dose-additivity, using the single chemical dose-response information on benzene and toluene. The endpoints included heart rate, heart rate progression, and lethality. Results included a synergistic response for heart rate at 72 h of development, and either additivity or antagonism for all other endpoints at 96 h of development. This work uses an established statistical method to evaluate the toxicity of an environmentally relevant mixture to ascertain whether interaction effects are occurring, thus providing additional information on toxicity.
authors.affiliation: US Environmental Protection Agency, National Center for Environmental Assessment, Mail Stop 190, 26 W. Martin Luther King Dr., Cincinnati, OH 45268, USA.
authors.forename: Linda K
authors.initials: LK
authors.lastname: Teuschler
authors.forename: Chris
authors.initials: C
authors.lastname: Gennings
authors.forename: William R
authors.initials: WR
authors.lastname: Hartley
authors.forename: Hans
authors.initials: H
authors.lastname: Carter
authors.forename: Arunthavarani
authors.initials: A
authors.lastname: Thiyagarajah
authors.forename: Rita
authors.initials: R
authors.lastname: Schoeny
authors.forename: Chris
authors.initials: C
authors.lastname: Cubbison
mesh_terms: D000818:Animals; D001554:Benzene / Q000633:toxicity*; D004347:Drug Interactions; D005260:Female; D006321:Heart / Q000187:drug effects / Q000196:embryology*; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D015233:Models, Statistical; D009990:Oryzias / Q000196:embryology*; D014050:Toluene / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D014050:Toluene; D001554:Benzene