a- and 13-HCH can be determined separately from the other isomers, by gas chromatography with electron-capture detection, and other methods, after extraction by liquid/liquid partition and purification by column chromatography. Biodegradation and abiotic degradation (dechlorination) by ultraviolet radiation (UVR) occur in the environment, with the production of delta-3,4,5,6-tetrachlorohexene, and pentachiorocyclohexene, respectively. The breakdown process is slower than in the case of lindane.