PESTICIDES: OCCUPATIONAL EXPOSURE AND POTENTIAL IMPACTS ON ECOSYSTEM AND HUMAN HEALTH IN MERU COUNTY, KENYA

Abstract

ABSTRACT This study assessed the usage of pesticides and its impacts on ecosystems and human health through occupational exposure in selected farming communities in Imenti North, Imenti South and Buuri Sub-counties in Meru, Kenya, where horticultural crops including French beans, kales and tomatoes are grown intensively for export and local consumption. The study was done through use of questionnaire distributed to farmers, agricultural extension and health care workers in selected farms in the three Sub-counties. In addition, analysis of pesticide residues by GC-MS in samples of farm soil, French beans, kales and tomatoes, from randomly selected sites in the three Sub-counties was done. The survey established that various pesticides in the classes of organochlorines, organophosphates, carbamates, pyrethroids and fungicides, were used in the three Sub-counties, with the most frequently used ones (>60 respondents out of 173) being parathion, diazinon, permethrin, pirimiphos methyl, carbaryl, deltamethrin, dieldrin, methoxychlor, cypermethrin, propoxur and carbofuran. Some of these including dieldrin, parathion and carbofuran were used illegally because they have been banned. Although most farmers had general information on pesticide usage through various social groups and contact with agricultural extension workers, only 32–43 % of the farmers had received training on pesticide handling and use. Most farmers (65%) had knowledge of safe pesticide handling procedures including reading labels on packages and wearing protective clothing; but many farmers (44% in Buuri, 57% in Imenti South and 60% in Imenti North) did not wear the requisite protective clothing when applying pesticides. Agricultural extension workers (52%) and health care workers (59%) were trained in their work and had at least a certificate level qualification from a tertiary institution. Most agricultural extension workers (95%) and health care workers (71%) had experience of dealing with pesticides and knew how to administer 1st AID against pesticide poisoning, respectively. Farmers (26%) reported experiencing health effects after using pesticides, with most effects being felt after using dimethoate, malathion, carbofuran, carbaryl and heptachlor. There was a statistically significant (p < 0.05) association between various factors (availability of protective clothing, hiring of labourers, farm land size, expenditure on pesticides and expenditure on treatment, respectively) on intoxication from pesticide exposure. Analysis of organochlorine pesticide residues in soil, French beans, Kales and tomatoes sampled randomly from the selected sites found widespread contamination of soils with organochlorine pesticide residues, with total (Σall OCs analysed, in μg/Kg dry weight) ranging from 15.78 – 307.70 in Imenti North, 1.25 – 159.88 μg/Kg in Imenti South, and 14.96 – 106.13 μg/Kg in Buuri. However, organochlorine pesticide residues were not detected in any of the vegetables. Other pesticides, including chlorpyrifos, carbendazine, imidacloprid, acetaprimid, metalaxyl, diazinon, azoxystribin, triadimefon, acephate, thiamethoxim and diuron were found in farm soils, French beans, kales and tomatoes, with concentrations (in μg/Kg dry weight) in soil samples ranging from BDL (metalaxyl and azoxystrobin) – 13,030 (carbendazin). In French beans, kales and tomatoes, the concentrations (in μg/Kg wet weight) ranged from BDL – 290, with the highest being imidacloprid in tomatoes. The pesticide residue levels generally were very low and met the Maximum Residue Limits set by European Union and other countries, and posed no concern to human health. Risk assessment of the residues in terms of estimated daily intakes (mg/Kg BW/day) also confirmed no health risk in the population. However, it is recommended that preharvest intervals for the pesticides should be observed in the three Sub-counties to avoid long term exposure to consumers.