Fish neoplasms and environmental chemicals.

Abstract

Water has been used as a medium of disposal of agricultural, industrial and urban waste. The potential hazards of water-borne environmental chemicals sometimes include not only damage to the ecology, but well pose direct risks to human health. Polluted water may give rise to direct risks to humans through contamination of drinking water supplies and fish. Neoplasms of fish are histologically similar to those described in the mammals and classification schemes for human neoplasms have generally applied to fish neoplasms. Various types of tumor are inducible in experimental fishes by administrations of known chemical carcinogens. The studies on fish neoplasms from the view point of chemical carcinogenesis and environmental carcinogenesis were intiated during the course of the studies on hepatomas in hatchery-grown salmonids about 25 years ago. Since then, surveys and other studies on fish neoplasms in wild population have been elaborated in order to monitor and to detect water-borne environmental carcinogens at many sites in the world, especially in U.S.A. In the present reviews, reports regarding epizootic fish neoplasms in wild populations are summarized in a table and recent findings for which good evidence of a pollution etiology is presented in details. Those are case histories regarding hepatomas in sauger and walleye in a lake polluted by copper mining waste in U.S.A., hepatomas in tomcod at Hudson river estuary, hepatomas in English sole and in other fishes at Puget Sound, hepatomas in brown bullhead at the Black river estuary to the lake Erie, various types of neoplasms in the fishes at the Buffaro and Niagara rivers and eastern lake Erie, papillomas in black bullhead at a final oxidation pond of municipal sewage treatment plant, neuroblastoma in coho salmon at a hatchery supplied with chlorinated water and pigmented cell neoplasms in the croaker, Nibea mitsukurii inhabiting along the Pacific coast of Japan. On the basis of these facts the importance of researches regarding fish neoplasms are discussed from the view point of environmental carcinogensis.