Determination of neonicotinoid residues in hive products from Kiambu and Nairobi Counties, Kenya
Mulati, Protus Wanjala
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Information on pesticide residue occurrence in hive products is scanty or lacking yet it is important so as to safeguard human health from effects of pesticides. The aim of the study was to identify and quantify neonicotinoid residues in hive products. The study was undertaken for 6 months between (March-August, 2015) at Kiambu and Nairobi Counties. The objectives of the study were to find out the pesticides used in the cultivation of crops, the frequency of use and the concentration of neonicotinoids in honey and bee bread (pollen).The methodology used was a structured questionnaire which was used to find out the pesticides used and frequency of their application. A modified Quick Easy Cheap Rugged Safe (QuEChERS) and liquid chromatography tandem mass spectrometry (LC-MS/MS) were used to determine the presence and concentration of neonicotinoids. The Chi-square was used to test frequency of pesticide application on cultivated crops around the apiaries and T-test was used to perform a comparison between concentration of residues detected in honey, pollen and in different landscape structures as well as making comparisons with European Union Maximum Residue Limits (EU-MRL). The study results indicated commonly used pesticides are carbamates (32.4%), pyrethroids (14.6%), neonicotinoids (14.4%), herbicides (15.7%), fungicides (1.4%), acaricides (5.6%) and organophosphates (14.5%). Further, 26.4% of respondents used carbaryl carbamates, 13.2% use Karate, 12% thiamethoxam and 7.4% dichlorvos. Regarding frequency of application, 86% of respondents used the pesticides once every week, 12.5% fortnightly and 1.4% when available. Chi-square test showed no significant difference in the application frequency (p>0.05). Honey was contaminated with acetamiprid with the mean levels of 0.41μg/kg.Thiamethoxam concentration in honey ranged from undetectable to 47.8μg/kg in Thika IPM with mean of 19.81μg/kg and standard deviation 24.77. Concentration of acetamiprid compound ranged from 0.1 ppb in Lari, Gatundu, Ruiru, Thika, Kikuyu, Karura and Ngong forests to 0.5ppb in Thika IPM. The mean levels of neonicotinoid concentration in honey were found to be statistically significant when compared with EU maximum residue limits (50ppb) established for food products (p=<0.05). The results generally showed low levels of neonicotinoid insecticides in bee food across Kiambu and Nairobi County. There was significant differences in neonicotinoid concentrations between cultivated and forested landscapes (p=0.009) and also when compared with EU-MRL in food substances (p=0.001). On average, there were higher concentrations of neonicotinoids in hive products from apiaries in cultivated areas compared to forested areas. Pesticides were detected in honey at remarkably low levels, ranging from 0.32 - 0.50 parts per billion (ppb), except for thiamethoxam, which measured 47.80 ppb in pollen. Based on the study results, honey from the studied areas is safe for human consumption and the honey bees are not exposed to harmful levels of neonicotinoids. However, pesticides persist in the environment and their levels should be monitored regularly. Beekeepers in the study areas are therefore advised to use the agro-ecological approach in applying the pesticides.