Dissipation behavior, residue distribution, and dietary risk assessment of fluopimomide and dimethomorph in taro using HPLC-MS/MS

Dimethomorph is a morpholine broad-spectrum fungicide and effectively controls taro blight, cucumber downy mildew, rice blast disease, and others. Fluopimomide is a newly developed broad-spectrum fungicide to primarily control oomycetes and rhizoctonia diseases. Taro, one of the earliest cultivated crops, is a staple food in Africa, Oceania, and Asia. Recently, a commercial suspension concentrate formulation containing 15% fluopimomide and 25% dimethomorph has been registered in China, the second largest taro producer in the world. The objective of this study was to develop a high-performance liquid chromatography tandem mass spectrometry method to detect the residues of fluopimomide and dimethomorph concurrently in taro samples. The results showed that the average recoveries of fluopimomide and dimethomorph ranged from 83 to 108%, and relative standard deviations (RSD) ranged from 1 to 11%. The limit of quantitation (LOQ) was 0.01 mg kg^-1 for the two compounds. The dissipation results demonstrated that both fluopimomide and dimethomorph in taro degraded rapidly in taro fields, and the residues of the two fungicides were below the LOQ within 14 days post-application. The final residue levels of fluopimomide and dimethomorph in taro were lower than 0.066 mg kg^-1 28 days post-application. For dietary risk assessments, the dietary structure of different genders and age of people in China exposure risk assessment and whole diet exposure risk assessment shows that the risk quotient (RQ) values were substantially lower than 100%, suggesting that the long-term risks of fluopimomide/dimethomorph mixed formulation in taro at the recommended dosage were negligible. In summary, our combined results from the dissipation behaviors, terminal residues, and dietary risk assessments provide the critical empirical data for the establishment of the maximum residue levels (MRLs) of the two broad-spectrum fungicides in taro, a traditional food for African, Oceanic, and South Asian cultures.

Dissipation and Risk Assessment of Multiresidual Fungicides in Grapes under Field Conditions

Grapes are among the most popular fruits globally, and various fungicides are widely applied to grape crops. As such, the presence of multiple fungicide residues and dietary risks in grapes has become the focus of significant attention. In this study, an easy-to-implement and sensitive UPLC-MS/MS approach was developed to simultaneously determine pyraclostrobin, dimethomorph, cymoxanil, cyazofamid and its metabolite CCIM in grapes via QuEChERS. This approach achieved 78.1-106.0% recovery and a 0.01 mg kg^-1 limit of quantitation (LOQ). Field trials revealed that these compounds had degradation half-lives ranging from 0.9 to 13.3 days. And their terminal residues ranging from < LOQ to 1.36 mg kg^-1 were below the official maximum residue limit (MRL) in China. The short-term risk for each tested fungicide was below 54%. The long-term risk of individual chemicals ranged from 0.0086% to 3.1%, and their cumulative risk was 4.4%. Results indicated that the dietary risk of these fungicides in grapes was minor.

Occurrence and human health implications of chemical contaminants in vegetables grown in peri-urban agriculture

Recent studies have proven that vegetables cultivated in peri-urban areas are exposed to a greater concentration of organic microcontaminants (OMCs) and trace elements (TEs) than those grown in rural areas. In this study, the occurrence and human health risk of chemical contaminants (16 TEs and 33 OMCs) in edible parts of lettuce, tomato, cauliflower, and broad beans from two farm fields in the peri-urban area of the city of Barcelona and one rural site outside the peri-urban area were assessed. The concentration of TEs and OMCs (on fresh weight basis) ranged from non-detectable to 17.4 mg/kg and from non-detectable to 256 μg/kg, respectively. Tomato fruits showed the highest concentration of TEs and OMCs. Principal component analysis indicated that the occurrence of chemical contaminants in vegetables depended on the commodity rather than the location (peri-urban vs rural). Risk assessment using hazardous quotient (HQ) and threshold of toxicological concern (TTC) approaches showed that the risk for the consumption of target vegetables in the peri-urban area was low and similar to that observed for the rural site. Total HQ values for TEs were always below 1, and a minimum consumption of 150 g/day for children and 380 g/day for adults is required to reach the TTC due to the presence of pesticides. Further studies are needed to estimate the combined effect of TEs and OMCs on human health.

Dissipation and residues of fluazinam and dimethomorph in potatoes, potato plants, and soil, determined by QuEChERS ultra-performance liquid chromatography tandem mass spectrometry

Fluazinam and dimethomorph 35% suspension concentrate (SC) is a new combined fungicide formulation introduced in China to improve fungicidal efficacy and decrease the risk of resistance in potatoes. Fluazinam and dimethomorph dissipation and residues in potatoes, potato plants, and soil under field conditions were determined by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Fluazinam and dimethomorph 35% SC was applied at two doses to potatoes and soil in Ningxia Autonomous Region and Anhui Province, China. Fluazinam and dimethomorph dissipation fitted first-order kinetics, and the fluazinam half-lives in potato plants and soil were 3.3-5.4 and 9.4-9.5 days, respectively. The dimethomorph half-lives in potato plants and soil were 2.1-2.6 and 5.9-8.6 days, respectively. Fluazinam and dimethomorph 35% SC was sprayed onto potato plants three or four times at application rates of 420 and 630 g a.i. ha^-1 with 7 days between applications. Potato and soil samples were collected at 3, 7, and 14 days after the last application. Potatoes and soil had fluazinam concentrations of < 0.01 and < 0.05-0.183 mg kg^-1, respectively, and dimethomorph concentrations of < 0.01 and 0.129-0.677 mg kg^-1, respectively. The final fluazinam and dimethomorph concentrations in potatoes were below the EU maximum residue limits (0.02 and 0.05 mg kg^-1, respectively) 3 days after application. Fluazinam and dimethomorph can therefore be applied to potatoes at the recommended doses.