Evaluation of the risk of oral administration of residual amounts of insecticides after disinsection of food grain reserve
Authors: Serhieiev S.G. , Kravchuk O.P. , Kolontaeva N.V. , Grynko A.P. , Makarova O.A. 
Published: November 2019

Introduction. Treatment of grain reserves (GR) with insecticides at the beginning of storage is a common technology for combating insect pests. In Ukraine, deltamethrin (synthetic pyrethroid), pirimiphos-methyl and chlorpyrifos-methyl (organophosphorus compounds) are used for GR disinsection. The use of GR with residual insecticides can be a significant risk to human health. Objective of the study. To evaluate the risk of toxic effects after oral administration of residual amounts (RA) of insecticides after disinsection of food grain reserves.
Materials and methods. To identify the risk and evaluate the exposure, physical and chemical properties, LD50 per os, consumption rate of active substances (AS) of insecticides, ratio of consumption rate and LD50 per os, results of AS RA measurement in GR (gas-liquid chromatography), half-life of insecticides in grain (T50), ratio of possible daily intake (DI) of AS RA to allowable daily intake (ADI), processing factors (PF), daily consumption of grain products were analysed. An integral exposure vector (combining DDI, DI, T50) was calculated, which was evaluated according to the proposed scale.
Results. The coefficients of selectivity of insecticide action are obtained, physical and chemical properties contributing to AS stability in the processed grain, the relationship between the consumption rate and RA are determined. AS with the largest values of the integral exposure vector is established. Based on the relationship between theoretical DI and DDI both without and taking into account PF and daily consumption of grain products, AS with the highest and lowest exposure levels are determined.
Conclusions. AS have a sufficient selectivity of action: their effective consumption rates when protecting GR 180–640 times below LD50 per os. Low solubility in water, hydrolytic stability and high lipophilicity contribute to AS stability and their concentration in bran and germ seeds after processing GR. Due to high AS resistance per RA in grain at the end of the study (up to 90 days), the initial consumption rates, which increase in the range of deltamethrin — chlorpyrifos-methyl-pirimiphos-methyl, play an important role. With conservative evaluation, 80–90 days after the treatment, theoretical DI of deltamethrin did not exceed DDI, whereas DI of pirimiphos-methyl exceeded DDI by 5 times and chlorpyrifos-methyl — by 11 times. When exposed at the level of residues, the greatest risk is represented by insecticides with the highest values of the integral exposure vector — pirimiphos-methyl and chlorpyrifos-methyl. Upon a more realistic assessment, the largest exposure to pirimiphos-methyl is associated with the consumption of whole wheat bread (at DDI level), to chlorpyrifos-methyl — with the consumption of whole wheat bread with bran (2,4 and 2,3 times higher than DI, respectively); the smallest exposure level of pirimiphos-methyl and chlorpyrifos-methyl is possible when consuming white flour and white bread.
Upon exceeding the allowable value of DI theoretical level of insecticides with treated grain reserves in the period of its use as food raw materials, it is expedient to carry out studies on the content of insecticide RA in grain products in order to assess the exposure when consuming these products at the level of scientifically substantiated and accepted norms.
Key words: insecticides, grain stocks, risk assessment, exposure, oral intake.