Oil refinery effluents: evidence of cocarcinogenic activity in the trout embryo microinjection assay.

Extracts prepared from oil refinery effluents (soxhlet and XAD-2) were tested for carcinogenic potential by means of the rainbow trout (Salmo gairdneri) embryo-injection bioassay. No neoplasms were detected in fish given injections of refinery extracts alone (with and without exogenous rat S-9 activation). Refinery extracts coinjected with aflatoxin B1 induced elevated frequencies of hepatic neoplasms. This cocarcinogenic effect was most pronounced when aflatoxin B1 was preincubated with rat S-9 prior to injection. Effluent extracts coinjected with a direct-acting carcinogen [N-methyl-N'-nitro-N-nitrosoguanidine (CAS: 56-57-5)] did not increase the incidence of hepatic neoplasms (with and without exogenous S-9 activation).