Predicting toxicity equivalents in fish tissue

Toxicity equivalents is a measure of "dioxin-like" toxicity contributed by polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (dioxins), and polychlorinated dibenzofurans (furans). Calculation of toxicity equivalents require the use of analytical procedures that are expensive and slow, making them impractical for routine analysis. U.S. Environmental Protection Agency National Fish Tissue Study (2003) data were used to determine the most significant predictors of toxicity equivalents with multiple regression analysis. The strongest predictive model (P < 0.0001, R2 = 0.97) included five compounds (PCB-118; PCB-126; 2,3,7,8-TCDD; 1,2,3,6,7,8-HxCDD; 2,3,4,7,8-PeCDF). However, the required lower limit of detection for an analytical method measuring these congeners is 0.1 ppt and would not provide much benefit over the current analytical method. An alternative model (P < 0.0001, R2 = 0.68) that included three PCBs (PCB-138, PCB-153, PCB-118) would require a limit of detection of 1,000 ppt and be more practical. This research demonstrates that the measurement of selected compounds can be used to estimate toxicity equivalents and consequently serve as the impetus for the development of lower cost, rapid analytical methods for analysis of fish.