Lambda-cyhalothrin-loaded nanocapsules pose an unacceptable acute toxicological risk to zebrafish (Danio rerio) at the adult and larval stages but present an acceptable risk to embryos

Recently, size-controlled pesticide microcapsule (MC) delivery systems have played an important role in precision farming development; however, the potential environmental hazards of MCs with different particle sizes have not been fully characterized. In this study, we prepared a series of lambda-cyhalothrin (LC)-MCs with nano and micron-scale capsule sizes (average diameters of 209.4 nm, MC-N; 2.41 mu m, MC-S; 4.87 mu m, MC-M; and 12.41 mu m, MC-L). The assessment results showed that the release and sedimentation behavior of LC-MCs in water and toxicity to zebrafish at three life stages were all particle size-dependent. As the diameter distribution of approximately 100 nm extended to the micron scale (similar to 27 mu m), the capsules released more slowly and sunk more quickly in water. In addition, micron-sized LC-MC exposure resulted in significantly less fish mortality and malformations of larvae and embryos compared with nanosized LC-MC exposure. The highest accumulation of MC-N in the gill and the severest toxicity to larvae suggested that the smaller size and stronger permeability of nanocapsules would pose unpredictable consequences for nontargeted organisms. The obvious toxicological differences of LC-MCs toward aquatic organisms implies that regulating MC production in an appropriate size range is an important prerequisite for achieving efficient but safe pesticide applications.

Automated summary

This study prepared a series of LC-MCs with different particle sizes and evaluated their toxicity, revealing that the release and sedimentation behavior in water, as well as the toxicity to zebrafish, were all particle size-dependent. Exposure to micron-sized LC-MCs resulted in significantly lower fish mortality and malformations compared to nanosized LC-MCs, indicating the importance of regulating MC production in an appropriate size range for safe pesticide applications.