Technical endosulfan (6,7,8,9,10, 10-hexachloro-1,5,5a,6, 9,9a, hexahydro 6,9-methano-2,4,3-benodioxathiepin, 3-oxide) is a brown crystalline substance consisting of alpha- and beta-isomers in the ratio of approximately 7030. It is used in a formulated form as a broad-spectrum contact and stomach insecticide mainly in agriculture and, in some countries, in public health. The method of choice for its determination is gas chromatography combined with electron capture detection. The main source of exposure of the general population is food, but residues have generally been found to be well below the FAQ/WHO maximum residue limits. Because of its use in tobacco farming, smoking may be an additional source of endosulfan exposure.