Rapid Screening of Pesticide Residues in Organic-labeled and Conventional Vegetables in Southern Luzon, Philippines and Its Implication on Food Safety

Abstract

Pesticide residues on vegetables pose a major concern with regard to food safety. The Rapid Bioassay for Pesticide Residues (RBPR) is a spectrophotometric method used to rapidly screen residues of acetylcholinesterase-inhibiting pesticides – namely, organophosphates (OP) and carbamates (CM) in vegetable samples. In this study, RBPR was utilized to detect pesticide residues in organic-labeled and conventional vegetables from various markets and stalls in selected areas in Southern Luzon, Philippines from January 2016–March 2018. Samples (n = 443) that resulted in > 20% inhibition in RBPR, the value considered as a permissible error, were considered positive for OP and/or CM residues. Results showed that 70 (15.8%) out of 443 samples were positive based on RBPR. Vegetable stalls from Laguna and Quezon, and Laguna public markets got the highest positivity of samples. Based on the farming method, 18.3% (n = 262) were positive in the conventional samples, as compared to 12.2% (n = 181) in the organic-labeled samples. Positivity rate was observed to be highest in bitter gourd, pechay, and tomato. A few samples (n = 6) were then analyzed by gas chromatography–mass spectrometry (GC-MS) as a confirmatory test. One organic-labeled sample was found to have exceeded the existing MRL based on GC-MS analysis. Overall, the study showed the presence of pesticide residues in commonly consumed conventional and even organic-labeled vegetables in Southern Luzon. The positivity of many organic-labeled samples is of serious concern as it may indicate fraud or mislabel and non-compliance to principles of organic farming. This also highlights the critical need for extensive intervention strategies to limit the potential health risk to consumers. It is advised that pesticide residues be monitored on a regular basis and that farmers be educated about better pesticide safety procedures, particularly the importance of adhering to prescribed pre-harvest intervals (PHI).