Chlorpyrifos is among the most widely sold organophosphates in the agriculture sector worldwide. Static bioassays were performed in the laboratory to compare the acute toxicity between the technical grade (94% a.i.) and commercial formulation (20% EC) of chlorpyrifos to four freshwater organisms: the crustacean zooplankton Cyclops viridis, the oligochaete worm Branchiura sowerbyi, the gastropod Pila globosa, and tadpole larvae of Duttaphrynus melanostictus. The recovery of actual chlorpyrifos concentrations in water after 2 h of exposure to the nominal concentrations ranged from 82.98% to 88.56%. The commercial formulation (F) of chlorpyrifos was found to be 1.94 to 2.76 times more toxic than the technical grade (T). Based on 96 h LC50 values of T and F chlorpyrifos, C. viridis was found to be most sensitive (0.56 and 0.25 μg/L) and P. globosa as most tolerant (1482 and 536 μg/L) to chlorpyrifos. Changes in LC50 values of both T and F chlorpyrifos were noted in respect of exposure hours for the three aquatic invertebrates and the tadpole larvae of the toad. In conclusion, the acute toxicity of chlorpyrifos to some non-target freshwater organisms differs between technical grade and commercial formulations.
Keywords: Aquatic Organisms; Formulation; LC50; Organophosphates; Toxicity.
© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.