Effect-based approach for screening of chemical mixtures in whole blood of green turtles from the Great Barrier Reef.

Organisms are exposed to mixtures of both known and unknown chemicals which are diverse and variable, and thus difficult and costly to characterise and monitor using traditional target analyses. The objective of this study was to validate and apply in vitro effect-based methods by which whole blood can be used to screen internal exposure to such complex chemical mixtures. For this study, we used whole blood of green sea turtles (Chelonia mydas). To ensure the chemical mixture in blood is transferred with minimal losses or bias, we tested a modified QuEChERS extraction method specifically developed for multi- and non-target instrument analysis. The extracts were dosed to a battery of in vitro bioassays (AhR-CAFLUX, AREc32, NFκB-bla, VM7Luc4E2, Microtox), each with a different mode of action (e.g., AhR receptor mediated xenobiotics, NrF2-mediated oxidative stress, NFκB mediated response to inflammation, estrogen activity and baseline toxicity oxidative stress, respectively) in order to cover a wide spectrum of chemicals. Results confirmed the absence of interferences of the blood extract with the responses of the different assays, thus indicating the methods' compatibility with effect-based screening approaches. To apply this approach, whole blood samples were collected from green turtles foraging in agricultural, urban and remote areas of the Australian Great Barrier Reef. The effect-based screening revealed significant differences in exposure, with higher induction of AhR-CAFLUX, AREc32 and Microtox assays in turtles from the agricultural foraging ground. Overall, these results corroborated with concurrent health, target and non-target analyses in the same animals performed as part of a larger program. This study provides evidence that the proposed effect-based approach is suitable for screening and evaluating internal exposure of organisms to chemical mixtures. The approach could be valuable for advancing understanding on multiple levels ranging from identification of priority chemicals in effect-directed investigations to exploring relationships between exposure and disease, not only in sea turtles, but in any organism.