Dissipation and Risk Assessment of Propaquizafop in Ginseng under Field Conditions

Propaquizafop is a highly efficient aryloxy phenoxy propionate chiral herbicide. However, the use of propaquizafop, including its safe use methods, residue patterns, dietary risk assessment, and maximum residue limits, for ginseng, a traditional Chinese medicinal plant, has not been studied. An analytical method was established for the simultaneous determination of propaquizafop and its four metabolites in ginseng soil, fresh ginseng, ginseng plant, and dried ginseng using HPLC-MS/MS. This approach showed good linearity (R2 ranging from 0.9827 to 0.9999) and limit of quantification ranging from 0.01 to 0.05 mg/kg. The intra- and interday recovery rates of this method ranged from 71.6 to 107.1% with relative standard deviation ranging from 1.3 to 23.2%. The method was applied to detect residual samples in the field, and it was found that the degradation of propaquizafop in ginseng plants and soil followed a first-order kinetic equation. R2 was between 0.8913 and 0.9666, and the half-life (t1/2) ranged from 5.04 to 8.05 days, indicating that it was an easily degradable pesticide (T1/2 < 30 days). The final propaquizafop residues in ginseng soil, plants, fresh ginseng, and dried ginseng ranged from 0.017 to 0.691 mg/kg. A dietary risk assessment was conducted on the final propaquizafop residue in fresh and dried ginseng. The results showed that the chronic exposure risk quotient values were less than 100% for fresh and dried ginseng (1.15% for fresh ginseng and 1.13% for dried ginseng). This illustrates that the dietary risk associated with the use of 10% propaquizafop emulsifiable concentrate in ginseng is very low. Thus, applying 750 mL/ha of propaquizafop on ginseng could not pose an unacceptable risk to public health. The results of the present study support the registration of propaquizafop in ginseng.

Evaluation of confirmatory data following the Article 12 MRL review for quizalofop-P-ethyl, quizalofop-P-tefuryl and propaquizafop and modification of the existing maximum residue levels for quizalofop-P-tefuryl

The applicant Arysta Life Science Great Britain Limited submitted a request to the competent national authority in Croatia to evaluate the confirmatory data that were identified for quizalofop-P-tefuryl in the framework of the maximum residue level (MRL) review under Article 12 of Regulation (EC) No 396/2005 as not available. Since Article 12 data gaps were also set for the two other quizalofop-P variants sharing the same residue definitions for risk assessment and monitoring, EFSA included in the present assessment all quizalofop-P variants: quizalofop-P-ethyl, quizalofop-P-tefuryl and propaquizafop. Moreover, in the application submitted to Croatia, the applicant also included a request to modify the existing MRLs for quizalofop-P-tefuryl in grapes, sunflower seeds and soyabeans in accordance with Article 6 of Regulation (EC) No 396/2005. To address the data gaps, new data on hydrolysis efficiency of quizalofop-P-tefuryl, quizalofop acid, quizalofop-pentanoic acid and quizalofop-P-glycerate in different matrices of animal origin in accordance with the guidance document SANTE/2020/12830 Rev.1 were submitted, along with a validated analytical method for animal commodities. EFSA concluded that the data gap on validation of the efficiency of the extraction and hydrolysis included in the enforcement method of residues in livestock animal commodities was only fully addressed for muscle, poultry liver and eggs. Regarding plant commodities, the remaining data gaps were not addressed. EFSA also considered data gaps for quizalofop-p-ethyl in caraway as sufficiently addressed in the context of a previous MRL application. In general, the new information provided required a revision of the existing MRLs for several commodities of plant and animal origin. Further risk management considerations are required. Based on the risk assessment results, EFSA concluded that the short-term and long-term intake of residues resulting from the use of quizalofop-P-tefuryl according to the reported agricultural practices is unlikely to present a risk to consumer health.

Modification of the existing maximum residue levels for quizalofop (resulting from the use of propaquizafop) in lettuces and salad plants

In accordance with Article 6 of Regulation (EC) No 396/2005, the applicant Adama Agan Ltd submitted a request to the competent national authority in Italy to modify the existing maximum residue levels (MRLs) for propaquizafop/quizalofop in lettuces and salad plants to accommodate the intended SEU use of propaquizafop. The data submitted in support of the request were found to be sufficient to derive MRL proposals of 0.15 mg/kg for the intended SEU use of propaquizafop for the crops belonging to the crop group of lettuces and salad plants. The MRL proposals are expressed for a common residue definition that covers quizalofop and propaquizafop. Since the EU MRL is set at a higher level of 0.20 mg/kg, no modification of the MRL is currently required for the intended use. Adequate analytical methods for enforcement are available to control the residues of propaquizafop, expressed as quizalofop, in plant matrices under consideration. Based on the risk assessment results, EFSA concluded that the long-term and short-term intake of residues occurring in food from the existing uses of quizalofop-P-ethyl, quizalofop-P-tefuryl and propaquizafop and from the intended use of propaquizafop on lettuces and other salad plants, is unlikely to present a risk to consumer health.

Crystal structure of propaquizafop

The title compound, C₂₂H₂₂ClN₃O₅ {systematic name: 2-(propan-2-yl­idene­amino­oxy)ethyl (R)-2-[4-(6-chloro­quin­oxalin-2-yl­oxy)phen­oxy]propionate}, is a herbicide. The asymmetric unit comprises two independent mol­ecules in which the dihedral angles between the phenyl ring and the quinoxaline ring plane are 75.93 (7) and 82.77 (8)°. The crystal structure features C—H⋯O, C—H⋯N, and C—H⋯Cl hydrogen bonds, as well as weak π–π inter­actions [ring-centroid separation = 3.782 (2) and 3.5952 (19) Å], resulting in a three-dimensional architecture.