Environmental exposure to hexachlorobenzene in the USA.

Hexachlorobenzene (HCB) is a chlorinated hydrocarbon chemical which has various industrial and agricultural uses in the USA. The agricultural use of HCB as a fungicide is relatively minor and is being phased out, but HCB is still used directly in a few industrial processes and is a waste product or impurity associated with the manufacture of various chlorinated solvents and other registered pesticides. A review of available HCB data from ambient environmental monitoring networks (agricultural and urban soils, ambient air, fresh-water fish, starlings, ducks and ready-to-eat foods) of the National Pesticide Monitoring Program resulted in the following general conclusions: Actual mean residue levels of HCB were erratic or steady during the 1970s and showed no major upward or downward trends; The percentages of detectable HCB did show a trend in most of the environmental monitoring networks. The percentage of HCB in the environmental components examined generally increased from the early 1970s to the late 1970s, when it peaked, and then declined into the early 1980s, the most recently available data sets. The reason for the increase of HCB in several environmental components is not clear.