Accumulation of pesticides residues in oil during the storage of rapeseed

摘要

Although pesticides residues are rarely present in crude rapeseed oils and are eliminated during the different steps ofrefining,it is important to know the origin of these contaminations to minimize the risks through good management practices and education.A study led between 2003 and 2005 showed that the main contaminants were organophosphate compounds (dichlorvos,chlorpyriphos-methyl, pyrimiphos-methyl, malathion) and pyrethrinoids (deltamethrin) which are insecticides traditionally used for cereal grain treatments during storage. The French regulation does not authorize these insecticides for the treatment of stored oilseeds which have however an affinity for liposoluble chemicals and can pick these up from storages which have previously been treated or used to store treated cereal grains. We have measured the uptake of pesticides from treated cell walls by stored rapeseeds, using an experimental model:spraying of pyrimiphos-methyl (0,2 g of active material/m2) on metal sheets covered by a single layer of rapeseeds or wheat after a drying period of 24h and measure of pyrimiphos-methyl residues in seeds and grains after 8 and 29 days. The pyrimiphos-methyl content in rapeseed was 0,028 mg/kg at the beginning of the experience, 15 mg/kg at J+8 and 15 mg/kg at J+29 (MRL 0,05mg/kg). The pyrimiphos-methyl content in wheat was 0,062 mg/kg at the beginning of the experience, 15 mg/kg at J+8 and 17mg/kg at J+29 (MRL 5 mg/kg). It was concluded that the transfer of pyrimiphos-methyl is fast (the values are equal at J+8 and J+29 and similar in rapeseed and wheat). Extrapolation studies in small storage silos (capacities 10 and 30 tons) are in progress for evaluating the average values of pesticides that can be really detected in seeds and grains.