Malathion and diazinon levels in grain dust from New Orleans area grain elevators

Insecticides applied to grain may be present in dust generated during grain handling and could expose workers to high insecticide concentrations, or be fed to animals in the form of pelleted grain dust. Residual levels of two organophosphate insecticides, malathion and diazinon, were measured in 31 samples of grain dust collected from six terminal grain elevators along the Mississippi River in the New Orleans area. These grain elevator samples and additional spiked samples were extracted and analyzed by gas chromatography. The lower limit of detection for malathion was 0.1 micrograms/g and for diazinon, 0.01 micrograms/g. Recovery of malathion from samples spiked with less than 1 micrograms/g was erratic. Mean recoveries of both malathion and diazinon from spiked samples ranged from 83 to 92% at levels of 1 to 50 micrograms/g of dust. Samples of grain dust from the elevators contained 0.17 to 32 micrograms of malathion/g of dust, but diazinon was not detectable at the 0.01 micrograms/g limit of detection.