Insecticide residues cross-contamination of oilseeds during storage (second part)

CETIOM, Service Transformation et valorisation des graines, oléagineuses, 11 rue Monge, Parc industriel, 33600 Pessac

^* dauguet@cetiom.fr

Abstract

This article is a continuation of the article Insecticide residues cross-contamination of oilseeds during storage published in OCL vol. 14, n°6, November-December 2007. The last article presented the results obtained by an investigation on stored sunflower seeds, and this new work presents results on stored rapeseed. Pesticide residues are found in oilseeds and crude oils: they are mainly organophosphate insecticides (pirimiphos-methyl, malathion) used in empty storage facilities and for application to stored cereal grains. French regulation does not allow use of these insecticides on stored oilseeds. These residues arise from cross-contamination from storage bins and facilities, and not from illegal use. This uptake of insecticide residues from their storage environment by oilseeds can lead to levels that can exceed regulatory limits. An investigation in 13 grain storage companies allowed us to follow the course of 21 rapeseed batches, from their receipt at the storage facilities to outloading. Samples from each of these batches, made at outloading, were analysed by ITERG, looking for insecticide residues. Traceability of rapeseed established by storers allowed us to identify cross-contamination sources. Results are slightly different from those obtained the previous year on sunflower seeds. Substances discovered were mostly pirimiphos-methyl, and malathion, plus chlorpyriphos-methyl (two cases) and deltamethrin (one case). Pirimiphos-methyl was most commonly detected, and caused most cases of non-accordance with regulatory levels. Main cross-contamination hazard resulted from treatment of cereals at their receipt during the same period than rapeseed receipt, especially when these cereals treatments were frequent on that silo. Other situations led to cross-contaminations, but generally of lower levels: outloading of rapeseed after outloading of treated cereals, rapeseed stored in bin that contained previously treated cereals, empty bins and handling equipment treated before receipt of rapeseed.