| tumors in fish caught in polluted waters: possible explanations. | the largest excess in tumor incidence due to pollution (616%) was observed in the fish species: ictalurus nebulosis (the brown bullhead). extensive analysis of waters on the fox river in illinois disclosed a heavy chemical and physical organic and inorganic materials far exceeding state and federal minimal safety standards. additional tests showed the presence of numerous human viral agents in the fox river. certain chemicals in the water appear to be potential carcinogens for fish. two types of ... | 1975 | 1174315 |