Dietery risk assessment for exposure to pesticide residues in exotic vegetables sold in Nakuru town, Kenya

Abstract

Vegetables constitute an important part of the human diet as a source of nutrients such as vitamins. The emerging lifestyle changes and need to live a healthy life have led to increased consumption of vegetables. There are, however, growing concerns over the indiscriminate use of pesticides and lack of clear safety standards for maximum residue levels for vegetables sold in the local market. This study was done to assess human exposure to pesticide residues through consumption of exotic vegetables sourced within Nakuru County and sold in selected markets in Nakuru town. The study used cross sectional study design. It involved social survey using structured questionnaires on consumers, farmers and stakeholders and laboratory analysis of vegetable samples for pesticide residues. Structured questionnaires were used to get data on sources and consumption rates of most consumed vegetables and most commonly used pesticides. Sample extraction and residue analysis was done using AOAC official method 2007.01. Pesticides residue analysis was done using Reverse-phase High Performance Liquid chromatography. Peak areas of the curves were calculated using Motic Images plus 2.0 and recovery rates of pesticides were recorded. The hazard quotient and hazard index was also calculated. Frequencies were used to analyse data on most commonly used pesticides which were cypermethrin and lambda-cyhalothrin. Mean was used to analyse date on most consumed exotic vegetables which were Kales (Brassica oleracea var. acephala), Tomatoes (Solanum lycopersicum) and Spinach (Beta vulgaris subsp. cicla). Hazard quotients and indices were calculated to determine risk of exposure to the pesticide residues. Recovery rates of pesticides in the laboratory analysis ranged from 87.78% to 97.93% for cypermethrin and 90.65% to 95.72% for lambda-cyhalothrin. Mean residue concentration levels in samples ranged from 2.495mg/kg to 0.238mg/kg for cypermethrin and 0.352mg/kg to 0.119mg/kg for lambda-cyhalothrin. Most of the hazard quotients and hazard index value computed of the two pesticides were within the recommended value ≤1. It is recommended that farmers should be encouraged to adhere to Pre-harvest interval after spraying pesticides to reduce residue levels. KEPHIS, KEBS and Ministry of agriculture, fisheries and livestock should also set and monitor regularly maximum residue levels of pesticides in locally consumed commodities to protect the consumers