Neurotoxicity of chlorpyrifos and chlorpyrifos-oxon to Daphnia magna

Multi‐ and Trans‐Generational Effects on Daphnia Magna of Chlorpyrifos Exposures

“…2921‐88‐2; 99.5% purity) was purchased from ChemService. Both the multi‐ and transgenerational assays employed the same dosing regimen (0, 0.025, 0.05, 0.075, and 0.1 μg/L chlorpyrifos), which was chosen after conducting a series of acute assays and range‐finding chronic assays discussed in Maggio et al (2021). A steep acute dose–response curve indicated that D. magna response to chlorpyrifos exposures quickly transitioned from no response to mortality.…”

“…As an alternative, the accuracy and precision of the method used to prepare chlorpyrifos bioassay exposure concentrations is reported. As described in Maggio et al (2021), to evaluate method performance, 5 18‐L replicates of the median exposure solution (nominal concentration 0.05 μg/L) and highest chlorpyrifos exposure solution (nominal concentration 0.10 μg/L) were individually extracted through solid‐phase extraction disks and analyzed by gas chromatograph with mass selective detection. Extract analysis ( n = 5) for the chlorpyrifos median extract solution was 0.06 (±0.003) μg/L with a coefficient of variation (CV) of 4.89%, and extract analysis ( n = 5) for the chlorpyrifos highest extract solution was 0.12 (±0.010) μg/L with a CV of 8.98%.…”

“…In both the multi-and transgenerational assays, D. magna parent (F0) generation 21-day chlorpyrifos exposure at the highest treatment (0.1 μg/L) resulted in a statistically significant decrease in survival and a decrease in reproduction in the surviving organisms. Previous acute and chronic toxicity bioassays with this D. magna broodstock (Maggio et al, 2021) show a steep dose-response curve for survival following 48-h acute exposures between 0.1 and 1.0 μg/L, and no treatment effects on survival or reproduction following 21-day chronic exposures below 0.1 μg/L. In addition, 21-day chronic exposure range-finding studies (Maggio et al, 2021) suggest a very narrow chlorpyrifos exposure range (0.1-0.2 μg/L) that may result in measurable effects on fitness.…”

“…Previous acute and chronic toxicity bioassays with this D. magna broodstock (Maggio et al, 2021) show a steep dose-response curve for survival following 48-h acute exposures between 0.1 and 1.0 μg/L, and no treatment effects on survival or reproduction following 21-day chronic exposures below 0.1 μg/L. In addition, 21-day chronic exposure range-finding studies (Maggio et al, 2021) suggest a very narrow chlorpyrifos exposure range (0.1-0.2 μg/L) that may result in measurable effects on fitness.…”

“…In addition, bioassays conducted with ecologically relevant concentrations of chlorpyrifos can describe a potential population-level response to environmental exposure scenarios. For example, Maggio et al (2021) reported a likely range of chlorpyrifos in US surface waters, which ranged from 0.003 to 0.4 μg/L, with a median value of 0.01 μg/L and 99th percentile of 0.17 μg/L, based on analysis of measured environmental concentrations (MECs) between 1992 and 2012 reported by the US Geological Survey (USGS; Vecchia, 2018). These chlorpyrifos MECs were compared with the D. magna 48-h acute bioassay with treatments ranging from 0.1 to 1.0 μg/L resulting in a median lethal concentration (LC50) of 0.76 μg/L and benchmark dose level, the lower 95% confidence limit of the benchmark dose, of 0.58 μg/L.…”