Atmospheric Concentrations of Hexachlorobenzene and Octachlorostyrene Are Uniform across the Great Lakes Region and Have Not Changed Much in 25 Years

Hexachlorobenzene (HCB) was used in the United States from 1945 to 1966 as a fungicide on wheat, while octachlorostyrene (OCS) was never marketed. However, both HCB and OCS continue to be emitted into the atmosphere as byproducts of several industrial processes. We have measured the atmospheric concentrations of HCB and OCS in samples collected every 12 days at five sites on the shores of the North American Great Lakes since 1991. The geometric mean concentrations of HCB and OCS are ∼60 and 0.7 pg/m 3, respectively, at all sites regardless of the local population, and these concentrations have not changed significantly over time. The concentrations of HCB measured here are similar to those reported by other studies of the northern troposphere and are ∼3 times those reported in the southern troposphere, suggesting that HCB sources are largely in the Northern Hemisphere. It is apparent that direct and recycled emissions of HCB and OCS into the northern troposphere are widespread in scope and, despite the elimination of HCB as a fungicide, have not changed in a meaningful way in the past 20–30 years. This is unlike the case for other legacy chemicals, for which global restrictions on their use have been more effective.