Acute toxicity and first tier risk assessment of four neonicotinoid insecticides to honeybees
The acute toxicities of 4 neonicotinoid insecticides (technical materials and formulations) including imidacloprid,thiamethoxam,clothianidin and acetamiprid to Apis mellifera adult worker honey bees were determined by ‘ oral-feeding tube’ and topical application methods,and the first tier risk assessment was carried out by using a parameter of hazard quotients (HQ).The results showed that the oral toxicity 48 h-LD50 values of 97.3% imidacloprid technical,25% imidacloprid WP,96% thiamethoxam technical,30% thiamethoxam SC,97% clothianidin technical,5% clothianidin WP,96% acetamiprid technical,40% acetamiprid SP to honeybees were 8.04 × 10-3,9.46 × 10-3,7.04 × 10-3,4.64 ×10-3,11.8 ×10-3,5.25 ×10-3,5.22,6.31 μg a.i./bee,respectively,and the acute contact toxicity 48 h-LD50 values were 2.46 × 10-2,1.33 × 10-2,3.63 × 10-2,9.27 × 10-3,1.52 × 10-2,2.21 × 10-2,5.82,5.07 μg a.i./bee,respectively.According to the toxicity criteria of ‘ Test Guidelines on Environmental Safety Assessment for Chemical Pesticides’,acetamiprid technical and acetamiprid SP had moderate acute toxicity,while the other 6 insecticides tested had high acute toxicity to honeybees.According to the HQ values the risk of acetamiprid to honeybees could be considered as low,while that of thiamethoxam,clothianidin and imidacloprid were high.