Cross-contamination of oilseeds by insecticide residues during storage

Abstract

Pesticide residues are found in oilseeds (rapeseed and sunflower) and crude oils: they are mainly organophosphate insecticides (pirimiphos-methyl, malathion) used in empty storage facilities and for application to stored cereal grains. Even if pests are found in stored oilseeds, 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 exceed regulatory limits. A two-year investigation in grain storage companies allowed us to follow the course of 27 sunflower batches (storage season 2006-2007) and 21 rapeseed batches (storage season 2007-2008), from reception 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 oilseeds established by storers allowed us to identify crosscontamination sources. Substances discovered were mostly pirimiphos-methyl, and malathion, dihlorovos (in sunflower), plus chlorpyriphos-methyl and deltaméthrine (one case). Pirimiphos-methyl was most commonly detected, and caused most cases of non-accordance with regulatory levels in rapeseed. Main cross-contamination hazard resulted from treatment of cereals at their receipt during the same period of rapeseed receipt, especially when these cereals treatments were frequent on that elevator. For sunflower, main cross-contamination hazard resulted from treatment of cereals at outloading, just before sunflower seeds were outloaded, especially when these cereals treatments were frequent on that elevator. Other situations led to cross-contaminations, but generally of lower levels: oilseeds stored in bin that contained previously treated cereals, empty bins and handling equipment treated before receipt of oilseeds.