Determination of bromothalonil residues and degradation in apple and soil by QuEChERS and GC-MS/MS

Dissipation Behavior, Residue, and Risk Assessment of Benziothiazolinone in Apples

Benziothiazolinone is the first independently developed fungicide in China. It has been used to effectively control fungal diseases in a variety of fruits, vegetables, and crops. In this study, the degradation behavior and final residue of benziothiazolinone in apples is discussed, and the dietary risk to consumers was evaluated. High-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine benziothiazolinone residues in apple samples from eight different regions of China. The average recovery of benziothiazolinone in apples was 85.5-100.2%, and the relative standard deviation (RSD) was 0.8-14.9%. The limits of the method of quantification of benziothiazolinone in apples was 0.01 mg/kg. Under good agricultural practices (GAP) conditions, the final residues of benziothiazolinone in apples were below 0.01 mg/kg, lower than the maximum residual limit (MRL) of China. Although the degradation half-lives of benziothiazolinone were 23.9 d-33.0 d, the risk quotient (RQ) of benziothiazolinone was 15.5% by calculating the national estimated daily intake and comparing it with the acceptable daily intake. These results suggested that under GAP conditions, the intake of benziothiazolinone from apples exhibits an acceptably low health risk on consumers.

Systemic stereoselectivity study of bromothalonil: stereoselective bioactivity, toxicity, and degradation in vegetables and soil

BACKGROUND

The chiral pesticide bromothalonil is widely used to control anthracnose disease on fruits and vegetables in China. The pesticidal activity, ecotoxicological effects and environmental behavior of bromothalonil and its enantiomers are still unclear.

RESULTS

Bromothalonil presented effective biocidal activities against the tested fungi, its enantiomers showed distinct inhibitory activities against different fungal species. The bioactivities of (+)-bromothalonil was 1.29-10.77 times higher than (-)-bromothalonil toward Rhizoctonia solani, Botrytis cinerea, Curvularia lunata, Corynespora cassiicola, Colletotrichum siamense, and Colletotrichum musae, while the effect pattern was opposite for Colletotrichum cliviicola. Based on the acute toxicity test, bromothalonil was very toxic to Eisenia foetida (E. foetida). Bromothalonil also damaged the lysosomal membrane and exhibited potential genotoxicity toward E. foetida. Moreover, (+)-bromothalonil presented lower toxicity than (-)-bromothalonil. Stereoselective degradation was investigated in tomato, cucumber, chieh-qua, and soil. The half-life values of bromothalonil degradation ranged from 7.14 to 24.75 days, indicating that bromothalonil was easily degraded. Additionally, (+)-bromothalonil degraded 1.2-1.75 times faster than (-)-bromothalonil in the four matrices.

CONCLUSION

This is the first systemic assessment of the stereoselectivity of bromothalonil. Based on the obtained half-life, EC₅₀ and LC₅₀ values, bromothalonil is an easily degraded, broad-spectrum biocidal but very toxic pesticide. (+)-Bromothalonil was more degradable in vegetables and soil and showed clearly higher bioactivity toward target organisms and lower toxicity to E. foetida than (-)-bromothalonil. Therefore, the stereoselectivity of bromothalonil enantiomers should be fully considered in comprehensive environmental and ecological risk assessments in future work. © 2020 Society of Chemical Industry.

Toxic Effects of Bromothalonil and Flutolanil on Multiple Developmental Stages in Zebrafish

In this study, we applied various developmental stages of zebrafish to address the potential environmental risk and aquatic toxicity of bromothalonil and flutolanil. This results demonstrated that the acute toxicity of bromothalonil to the three phases of zebrafish were 4.34 (embryo) < 3.27 (12 h old larvae) < 2.52 mg/L (adult fish) and that of flutolanil were 5.47 (embryo) < 4.09 (72 h old larvae) < 3.91 (12 h old larvae) < 2.70 mg/L (adult). Sublethal effects induced by both bromothalonil and flutolanil on zebrafish embryos were noted, including growth inhibition, abnormal spontaneous movement, slower heart rate, complete hatching failure, and morphological deformities. In addition, both bromothalonil and flutolanil could cause notochord deformation and short body length of larvae. This study provides a foundation for future investigation into the mechanism of bromothalonil and flutolanil toxicity in zebrafish.

Distribution of chlorpyrifos in rice paddy environment and its potential dietary risk

Chlorpyrifos is one of the most extensively used insecticides in China. The distribution and residues of chlorpyrifos in a paddy environment were characterized under field and laboratory conditions. The half-lives of chlorpyrifos in the two conditions were 0.9-3.8days (field) and 2.8-10.3days (laboratory), respectively. The initial distribution of chlorpyrifos followed the increasing order of water<straw<soil, and soil was characterized as the major absorber. The ultimate residues in rice grain were below the maximum residue limit (MRL) with a harvest interval of 14days. The chronic exposure for chlorpyrifos was rather low compared to the acceptable daily intake (ADI=0.01mg/kg bw) due to rice consumption. The chronic exposure risk from chlorpyrifos in rice grain was 5.90% and 1.30% ADI from field and laboratory results respectively. Concerning the acute dietary exposure, intake estimated for the highest chlorpyrifos level did not exceed the acute reference dose (ARfD=0.1mg/kg bw). The estimated short-term intakes (ESTIs) were 0.78% and 0.25% of the ARfD for chlorpyrifos. The results showed that the use of chlorpyrifos in rice paddies was fairly safe for consumption of rice grain by consumers.

Analysis of cyazofamid and its metabolite in the environmental and crop samples using LC-MS/MS

A rapid and robust LC-MS/MS method for the analysis of cyazofamid and its metabolite, 4-chloro-5-p-tolylimidazole-2-carbonitrile (CCIM), in environmental samples (soil and water) and a variety of crops (apple, mandarin, Kimchi cabbage, green pepper, potato and soybean) was established in this study. Those compounds were analyzed by selected reaction monitoring with electrospray ionization (positive mode) on LC-MS/MS. Method limit of quantitations were 2 ng g(-1) (cyazofamid) and 5 ng g(-1) (CCIM) for soil/crop samples, while 0.02 ng mL(-1) (cyazofamid) and 0.05 ng mL(-1) (CCIM) were achieved for water samples. Matrix effect (%) was different depending on sample matrices. For recovery tests, soil/crop samples were treated with QuEChERS method and water samples were extracted with dichloromethane. The recoveries of target analytes in the environmental and crop samples were 80.2 %-105.1 % for cyazofamid and 75.1 %-99.1 % for CCIM (coefficients of variation; ≤16.4 %).