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The Physiochemical Properties of Organophosphorus Pesticides Can Predict Some of the Developmental Toxicity Profiles in Zebrafish
Citation:
Waalkes, M., D. Hunter, K. Jarema, J. Hedge, AND S. Padilla. The Physiochemical Properties of Organophosphorus Pesticides Can Predict Some of the Developmental Toxicity Profiles in Zebrafish. Carolinas SETAC, Charleston, South Carolina, May 17 - 19, 2017.
Impact/Purpose:
Ascertaining how the physiochemical properties of the chemicals influence their toxicity would allow us to predict the toxicity of untested chemicals. We compared the physiochemical properties of a group of organophosphorus pesticides and found that we could predict some of the toxic outcomes, but not all, so the physiochemical properties are useful in some instances but not in others.
Description:
The Environmental Protection Agency is screening environmentally relevant chemicals for both developmental and neurodevelopmental toxicity using zebrafish (Danio rerio). Ascertaining how the physiochemical properties of the chemicals influence the toxicity profile in developing zebrafish may allow us to predict the toxicity of untested chemicals. Physiochemical properties of 26 organophosphorus pesticides (final concentration ≤100µM) were compared to their developmental toxicity and developmental neurotoxicity. For all experiments, zebrafish embryos were placed in 96-well plates and exposed to the chemicals during the initial 4 days of development, with the solution renewed each day. Assessments occurred 6 days post-fertilization (dpf). For developmental toxicity, mortality, hatching, and malformations were assessed. To evaluate developmental neurotoxicity, only nonlethal, sub-teratogenic concentrations were administered, and a locomotor assay using sequential light/dark photoperiods was used to assess neurodevelopmental integrity. Results revealed that the more lipophilic pesticides (i.e., the ones with a higher LogP) showed an increased likelihood (hit/no hit) of exhibiting developmental toxicity but not neurodevelopmental toxicity. Whether that chemical was the parent chemical or oxon (active metabolite) was not associated with the likelihood of either toxicity. A sensitivity/specificity analysis showed that if a pesticide was developmentally toxic, it was likely to be neurodevelopmentally toxic (0.75), but the negative correlation between developmental and neurodevelopmental toxicity was poor (0.33). These findings show that physiochemical properties of this group of pesticides are limited with respect to predicting their toxicity profile. This abstract may not necessarily reflect official Agency policy.