Mean sampler concentrations of hexachlorocyclohexanes (HCHs) in the atmosphere of North America during 2000/01 (Sable Island is sample location "7"). These two formulations of HCH have been used as commercial insecticides: α-HCH (technical HCH) was used globally until the 1970s, but was phased out over a decade ago; and γ-HCH (lindane) was banned in many countries, but is still used in North American agriculture, particularly in Canada. Figure: Shen et al. 2004.