Rainbow trout cell bioassay-derived relative potencies for halogenated aromatic hydrocarbons: Comparison and sensitivity analysis

Rainbow trout hepatoma cells, stably transfected with a luciferase reporter gene under control of dioxin‐responsive elements (RLT 2.0 cells) were used to derive relative potencies (RPs) for a variety of halogenated aromatic hydrocarbons (HAHs) that are structurally similar to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD). This in vitro bioassay utilizes 96‐well microplates, which provide high sample throughput and assay efficiency without affecting sensitivity. The RLT 2.0‐derived potencies for dioxin and furan congeners, relative to 2,3,7,8‐TCDD, ranged from 0.917 for 1,2,3,4,7,8‐hexachlorodibenzofuran to 0.208 for 1,2,3,7,8‐pentachlorodibenzofuran. All mono‐ and di‐ortho polychlorinated biphenyls (PCBs) tested had RPs that were orders of magnitude less than TCDD, but point estimates could not be determined. The RLT 2.0‐derived RPs were found to be comparable to both other rainbow trout‐specific RPs and RPs based on mammalian bioassays. Sensitivity analysis suggested that the range of uncertainty associated with TCDD equivalent (TEQ) estimates based on RLT 2.0‐derived RPs is approximately 10‐fold. Within this degree of uncertainty and the context of this study, the RLT 2.0 bioassay showed no definitive biases or inaccuracies relative to similar mammalian‐ or fish‐specific in vitro bioassays. Thus, the RLT 2.0 bioassay appears to be a useful tool for evaluating dioxinlike potency of HAHs to fish.