Dissipation Kinetics and Risk Assessment of Paclobutrazol in Onion

Paclobutrazol is used as both a fungicide and growth regulator in onion, its residue persistence raises concerns for food safety and environmental health. A field study was conducted to estimate the residues of paclobutrazol on onion crop. Two foliar sprays of Paclobutrazol 23% SC with 15 days interval were applied at recommended dose (X) i.e. 34.5 g a.i. ha^- 1 and 1.25X recommended dose i.e. 43.13 g a.i. ha^- 1 in onion, Samples were collected at different intervals to estimate dissipation and persistence of paclobutrazol. QuEChERS method was used to extract residues which were further estimated via LCMS/MS. Initial residues were observed to be 0.29 and 0.35 mg kg^- 1 in samples applied with X and 1.25 X dose. Residues of paclobutrazol reached below LOQ (limit of quantification) at 10th day at X dose and 15th days of sampling at 1.25X dose after last application. Residues of paclobutrazol were below the LOQ in mature onion and soil samples collected at harvest. Dissipation kinetics showed that paclobutrazol residues dissipated via first order kinetics at both the doses. T_1/2 (half-life) of paclobutrazol was calculated to be 4.57 and 5.04 days, at X Dose and 1.25 X Dose respectively, in green onion. Dietary risk assessment showed the hazard quotient (HQ) observed at both the doses was less than 1 for both adults and children.