Comparative study on the toxicity of pyrethroids, α-cypermethrin and deltamethrin to Ceriodaphnia dubia.

Two synthetic pyrethroid pesticides, α-cypermethrin and deltamethrin were investigated as potential toxic contaminants. The acute and chronic bioassays were conducted using Ceriodaphnia dubia. The toxicity of α-cypermethrin and deltamethrin to C. dubia increased with increasing concentrations and exposure time. C. dubia was three times more sensitive to deltamethrin than to α-cypermethrin with 48-h EC(50) of 0.06 μg/L and 0.23 μg/L, respectively. The chronic EC(50) values for α-cypermethrin and deltamethrin were 97.8 and 34.7 ng/L, respectively. Eight-day growth of Ceriodaphnia neonates during chronic exposures was the most sensitive endpoint measured in comparison to the endpoints of survival and number of neonates produced. To gain a better understanding of the link between acute and chronic toxicity, the acute-to chronic ratios (ACRs) were also calculated for survival, growth and reproduction endpoints. ACRs varied between 11 and 224 for the two pyrethroids. These results suggest that at environmentally relevant low concentrations, α-cypermethrin and deltamethrin could have significant adverse effects on the survival, reproduction and growth of C. dubia. Crown