The Risk of Dietary Exposure to Pesticide Residues and Its Association with Pesticide Application Practices among Vegetable Farmers in Arusha, Tanzania

Abstract

This study was conducted to assess dietary exposure to pesticide residues and pesticide application practices leading to the presence of these residues among vegetable farmers in Arusha, Tanzania. Face-to-face interviews using semi-structured questionnaires (including 24-hour recall and food frequency questionnaire techniques) were conducted to collect information on pesticide application practices and vegetable consumption, from 76 farmers. A sample of ready-to-eat vegetables was collected from each farmer's household to determine the level of pesticide residues. Pesticide residues were analyzed by gas chromatography-mass spectroscopyA deterministic approach was used to assess dietary exposure to pesticide residues. Among the analyzed samples, 31.4% contained detectable levels of organophosphate residues. The detected organophosphates were dimethoate (mean, 8.56 mg kg-1), acephate (mean, 2.9 mg kg-1), profenofos (mean, 8.44 mg kg-1), dichlorvos (mean, 20.8 mg kg-1) and malathion (mean, 5.47 mg kg-1). The mean exposure for dimethoate (0.0021 mg kg-1 body weight (wt) day‑1 was higher than its corresponding acceptable daily intakes of 0.002 mg kg-1bwd‑1 resulting in hazard quotient of 1.044 with a consequent hazard index of 1.19 for organophosphates. Pyrethroid pesticides (permethrin, cypermethrin, and lambda-cyhalothrin) were also detected but at a lower frequency (17.1%) and hazard index (0.029). The exposure to pesticide residues was significantly associated with limited access to expert advice on pesticide application (p=0.031, adjusted odds ratio=6.56) and over-dosage (p=0.038, adjusted odds ratio=3.751).The risk may be minimized by increasing access to support by extension service providing guidance on good practices and ensuring application of appropriate doses for pesticides.

Household vegetable processing practices influencing occurrence of pesticide residues in ready‐to‐eat vegetables

“…Given a provision of 3 years from 2011 implies that, endosulfan should have been stopped from the use by 2014. However, a survey done in Arusha district in 2015 revealed that farmers were still applying this pesticide in vegetables (Kiwango et al, ), indicating a need for improved reinforcement of pesticide use management regulations.…”

“…This indicates that farmers did not observe the preharvest interval after pesticide application. Kiwango et al () and Mhauka () report that most of the vegetable farmers do not adhere to the preharvest interval. Quantifying pesticide residues in vegetables at levels above MRL implies that the consumers are exposed to levels of health concern.…”

“…This is one of the famous areas for vegetable production in the country, where farmers apply pesticides intensively (Lekei et al, ). Vegetables produced in Arusha include cabbages, spinach, pumpkin leaves, Ethiopian mustard, Amaranthus spp ., and African nightshade (Kiwango et al, ). Arusha city is one of the major markets for vegetables produced in Northern Tanzania.…”

“…Individuals residing in Arusha city and willing to participate in the study were recruited as prospective respondents. A sample size of 65 was calculated to give a statistical power of 0.8 following Equation (1), where N is sample size, Z is the number of SD s above or below the population mean, P is prevalence of pesticide residues in vegetables (in this case, 40% prevalent obtained from the study in Arusha district (Kiwango et al, ) was used and δ is confidence interval (source: https://www.surveysystem.com/sample-size-formula.htm). …”

“…To ensure that pesticides residues in foods comply with the set maximum limits, actors along the food chain, have to observe good agricultural and food preparation practices. It is reported that in Tanzania most of the vegetable farmers do not follow good agricultural practices (Kiwango, Kassim, & Kimanya, ). For example, studies conducted in Arusha and Meru districts of Tanzania (Kariathi, Kassim, & Kimanya, ; Kiwango et al, ; Lekei, Ngowi, & London, ) reported that farmers in this region apply pesticide indiscriminately or do not observe the preharvest interval; a period between pesticide application and harvest, resulting in pesticide residue levels above MRLs.…”