Hazard assessment of the neonicotinoid insecticide thiamethoxam residues in tomato: a prelude to risk assessment profile

• Published in: Toxicological and environmental chemistry 2014-02, Vol.96 (2), p.318-327
• Main Authors: Malhat, Farag M., Watanabe, Hirozumi, Loutfy, Naglaa M., Ahmed, Mohamed Tawfic
• Format: Article
• Language: English
• Subjects: Chromatography; Diet; dissipation; hazards; Health hazards; HPLC (DAD); Insecticides; Lycopersicon esculentum; residues; thiamethoxam; Tomatoes
• ISSN: 0277-2248; 1029-0486
• DOI: 10.1080/02772248.2014.932522

A minor modification to the QuEChERS (quick, easy, cheap, effective, rugged and safe) method was carried out for the analysis of thiamethoxam in tomato using high performance liquid chromatography equipped with a diode array detector (HPLC-DAD). The method showed a good linearity with a determination coefficient (R 2 ) of 0.999 for the 0.02-5 mg/L concentration range. The method was validated using a blank tomato spiked at 0.05, 0.1 and 0.5 mg/kg, and the average recovery rate was 96%-99%. The limits of detection and quantification were 0.02 and 0.05 mg/kg, respectively. In this study, dissipation and residual levels of thiamethoxam in tomato under open field conditions were investigated. Thiamethoxam residues tend to dissipate following first-order rate kinetics with a half-life of 2.34 days. At harvest time, the remaining residues of thiamethoxam were below the European Union (EU) maximum residue level of 0.2 mg/kg when measured 14 days after the final application. Exposure of thiamethoxam was determined and compared to acceptable daily intake (ADI). The assessment of consumer exposure was based upon the estimated daily intake (EDI) which was compared to ADI and expressed as percentage. Based upon tomato consumption, the EDI of thiamethoxam ranged from 8.82 × 10 −6 to 3.38 × 10 −4 mg/kg b.w./day, which corresponds to 0.08% and 3.3% of ADI, respectively. Since the dietary exposure never exceeded 4% ADI, the tomato fruit may be considered safe for human consumption after application of the recommended dose of thiamethoxam.