Advanced risk assessment for aquatic ecology of single-dose of pyraclostrobin registered on four crops

The current situation of single-dose pyraclostrobin products registered on rice, wheat, citrus and potato in China were analyzed, and the exposure concentration in surface water was predicted by using Top-Rice and China-Psem models, as well as their advanced risk to aquatic ecosystem were assessed. The results showed that as of May 2021, there were 25 formualtions of pyraclostrobin registered on four crops in China, which were divided into 5 groups. The proportion of suspension concentrate (SC) was the largest, accounting for 52%, followed by emulsifiable concentrate (EC), accounting for 20%, microcapsule suspension (CS), water dispersible granule (WG) and wettable powders (WP) accounted for 16%, 8% and 4%, respectively. The application range of different formulations of pyraclostrobin and the exposure assessment of different groups on the four crops were investigated, according to the conservative principles of risk assessment. The results showed that the predicted environmental concentration (PEC) of pyraclostrobin on rice ranged from 0.07 to 1.24 μg/L in different scenarios and seasons, the predicted environmental concentration of pyraclostrobin used on wheat ranged from 0.45 × 10⁻³ to 0.60 μg/L, the predicted environmental concentration of pyraclostrobin used on citrus ranged from 0.03 to 0.76 μg/L, and the predicted environmental concentration of pyraclostrobin used on potato ranged from 0.01 to 0.94 μg/L. Under the current registered application conditions, the risk characterization showed that pyraclostrobin was used on four crops for the recommended method, dosage and number of times, the risk was acceptable. However, in view of its high toxicity to aquatic organisms, the dosage and frequency of application on paddy fields should be cautious, as it poses certain risks to aquatic ecosystems. In the present study, the analysis of its application method mode was conservative, which might be underestimeated the evaluation result in some way.