You are here:
Nine and Ten chemical haloacetic acid mixtures exhibit concentration-dependent departure from dose additivity
Citation:
SIMMONS, J. E., C. Dingus, E. D. Wagner, L. K. Teuschler, G. Rice, AND M. J. Plewa. Nine and Ten chemical haloacetic acid mixtures exhibit concentration-dependent departure from dose additivity. Presented at Society of Toxicology 49th Annual meeting, Salt Lake City, UT, March 07 - 11, 2010.
Impact/Purpose:
We assessed the validity of an assumption of dose addition for 4 HAA mixtures: environmentally relevant mixtures of the 9 HAAs combined at mixing ratios representative of postchlorination (CL) and preozonation/postchlorination, as well as equimolar mixtures of the 9 common HAAs (9HAA EQM) and a 10 HAA mixture (1OHAA EQM) comprised of the 9 common HAAs and IA. The individual HAAs and the HAA mixtures were evaluated in a Chinese Hamster Ovary cell chronic cytotoxicity assay at a minimum of 10 concentrations each.
Description:
Disinfection of water greatly decreases waterborne disease. Disinfection byproducts (DBPs), including haloacetic acids (HAAs), are formed when oxidizing disinfectants react with inorganic and organic matter in water. Water providers routinely assay for 9 HAAs in finished drinking water: chloro-, dichloro-, trichloro-, bromo-, dibromo-, tribromo-, bromochloro-, bromodichloro-, dibromochloro-acetic acid. Iodoacetic acid (IA) is a recently identified DBP. We assessed the validity of an assumption of dose addition for 4 HAA mixtures: environmentally relevant mixtures of the 9 HAAs combined at mixing ratios representative of postchlorination (CL) and preozonation/postchlorination, as well as equimolar mixtures of the 9 common HAAs (9HAA EQM) and a 10 HAA mixture (1OHAA EQM) comprised of the 9 common HAAs and IA. The individual HAAs and the HAA mixtures were evaluated in a Chinese Hamster Ovary cell chronic cytotoxicity assay at a minimum of 10 concentrations each. The individual HAA data were used to develop a smooth additivity model consistent with Berenbaum's definition of additivity. The fitted models provided reasonable fits to the single chemical data. The slope of the fitted dose-response curve for each individual HAA and HAA mixture was negative and statistically significant, indicating that cell density decreased significantly with increasing concentration. The overall test for departure from dose additivity was significant (p