Abstract:  Bees are key pollinators in agricultural ecosystems, and the association between their population decline and pesticide exposure has become a global research hotspot. Different types of pesticides have different toxic effects on bees. Conducting ecological risk assessment of pesticides on bees is particularly important for protecting bee populations. In this article, we reviewed the research progress of ecological risk assessment of pesticides on bees in the European Union, the United States and China from the aspects of exposure assessment, effect assessment and risk characterization. In the exposure assessment, the European Union, the United States and China have adopted different exposure models. Studies have shown that the European Union has achieved quantitative risk prediction through the parameterized exposure model and the three-level assessment system (from screening level to field test). The exposure model in the United States features multi-factor simulation, and assessment based on real-world data. China although has established its own assessment standards, it still has shortcomings in the accumulation of data on mixed toxicity assessment, bee colony dynamic models and native bee species. In effect assessment, the European Union, the United States and China all adopt an assessment approach from low to high levels, including individual toxicity effects, population toxicity effects and molecular toxicity effects. In risk characterization, the United States uses the risk quotient (RQ) for assessment ［RQ=Estimated environmental concentration (EEC)/median lethal dose (LD₅₀)］, and if RQ>level of concern (LOC), further assessment is required. The European Union uses the hazard quotient (HQ) ［HQ=Application rate (AR)/LD₅₀］ for assessment, and when HQ>50, advanced risk assessment must be conducted. In China, double-line assessment frame is adopted: in the spraying scenario, RQ=AR/LD₅₀×50, and in the soil or seed treatment scenario, RQ=Predicted exposure dose (PED)/predicted no-effect dose (PNED). If RQ≤1, the risk is considered acceptable, and if RQ>1, the risk is unacceptable. Overall, the European Union’s assessment system is relatively complete, including bumblebees and solitary bees in the assessment system, and covering methods and processes for risk assessment of pesticide metabolites and mixtures on bees. China should establish a relevant assessment system as soon as possible, improve assessment standards, and provide practical and feasible solutions for the effective management of pesticides and the protection of bee populations.

Key words:  Pesticide residues, bees, exposure model, toxic effects, ecological risk assessment