Concentrations and distribution of 3,3′-dichlorobenzidine and its congeners in environmental samples from Lake Macatawa

Release of 3,3′-dichlorobenzidine (DCB), an intermediate in dye manufacturing processes, is of environmental concern due to its carcinogenic nature. An 11-year field study has been conducted to elucidate the fate and behavior of DCB and its congeners in the Lake Macatawa (Holland, MI, USA) sediment–water system. The sediments were variable in composition, ranging from sandy sediments with 1–8.7% total organic carbon (OC) to silty-clay sediments with 7.5–20.6% total OC. The pH ranged from 6.3 to 7.4. The findings from this field study confirmed that DCB and its congener, benzidine, are transported over long distances. The concentration of DCB in the water phase was found to be from non-detectable to approximately 1300 times greater than the water quality criteria established for DCB (0.021 μg/l). Its congener, benzidine, which is substantially more toxic for humans than its parent compound has been found up to approximately 12 300 times higher levels than the EPA guidelines suggest (0.000086 μg/l). Both DCB and benzidine were found in the sediment phase. DCB was observed at almost 70 mg/kg in a sample collected in 1993. The concentrations in both phases have declined in recent years. To assess the threat of the released pollutants, it is necessary to understand how pollutants tend to behave in various media. Therefore, it is crucial to identify and quantify all sources of the chemical and its congeners in order to meaningfully predict the fate (and transport) of a hydrophobic organic compound (HOC) in the environment.