Several aspects of the aquatic environmental fate of 3,3'-dichlorobenzidine (DCB), a suspected human carcinogen, were examined. Greater than 95% of dichlorobenzidine present was adsorbed to natural pond and lake sediments in aqueous suspensions. Only a portion of the adsorbed chemical could be extracted from the sediments, with this amount decreasing over time, suggesting chemical reaction of DCB with sediment constituents. Dichlorobenzidine was rapidly degraded by natural and artificial light in aqueous solution, with a half-life of the order of 90 seconds in natural sunlight. Monochlorobenzidine and benzidine were found to be intermediate products of this process. In contrast, DCB appeared recalcitrant to degradation by naturally occurring aquatic microbial communities with only a minor loss of chemical detected over a 30-day incubation period. Dichlorobenzidine was rapidly bioconcentrated in bluegill sunfish, with mortality occurring prior to establishment of a chemical equilibrium between water and fish. Bioconcentration factors of 132-554 were achieved at this point. The only metabolite detected in the fish was an acid-labile conjugate of DCB. Based on these observations, chemical and physical processes, rather than biological ones, appear to be the important factors governing the fate of DCB in the aquatic environment. The ability of DCB to concentration in aquatic organisms may pose a direct hazard to human health through consumption of contaminated fish.

"EPA 600-3-78-068." "July 1978." Cover title. Includes bibliographical references (pages 46-49).