魚類に見られる脾血鉄症と化学工場排水との関連に関する一考察

1. Histological examinations were made on the common gobbies, Acanthogobius flavimanus, collected in the period from November of 1972 to December of 1973, from two rivers, the Higashi-okawa and the Nishi-okawa. Both the rivers flow, at Kure City, Hiroshima Prefecture, into the Hiro Bay adjoining the Aki-nada in the Seto Inland Sea. The Higashi-okawa was expected to be severely polluted by the waste from big chemical plants built along its banks, whereas the Nishi-okawa was not.

The results of the examinations were as follows;
A manifest hemosiderosis was observed in the spleens of all specimens from the Higashi-okawa but no such symptom was found in those from the Nishi-okawa. These results suggested some relation between the hemosiderosis in the spleens of fishes and a pollution caused by waste from chemical plant.

2. A series of experiments on a laboratory scale were carried out on Tilapia mossambica, a euryhaline species easier to handle in a laboratory than the goby, for the purpose of verifying the above suggested relation of the hemosiderosis in the spleens of fishes to chemical pollution.

The results were as follows;
a) A hemosiderosis was observed markedly in the spleens of the animals which had been exposed for only one month to dilutions of the waste from the Fukuyama plant of the Nihon Kayaku K.K. though the animals could keep their vital and spawning functions at normal level for more than six months in these dilutions: The degree of development of hemosiderosis appeared to depend upon concentration of waste in the dilutions. A hematological examination on the animals which showed hemosiderosis in the spleens revealed a hypochromic and microcytic anemia.

In the case of sudden death within 20 hours or so of exposure to dilutions of higher concentrations of waste, no hemosiderosis was found in the spleens of the animals, but other types of histopathological symptoms were noticed.

b) Phenol, one of the principal components of the waste from the Fukuyama plant of the Nihon Kayaku K.K., was found to be the causing factor of the hemosiderosis in the spleen of the animal; when exposed to a phenol solution with a chronic toxic level of concentration (2 ppm), the animal showed a manifest hemosiderosis in the spleen. However, at higher concentration above the acute toxic level (50 ppm), the exposure of the animals to phenol solution did not result in the hemosiderosis in the spleen but in other types of histopathological symptoms.

In conclusion, it should be emphasized that in the spleen of fishes exposed to waste from chemical plants, hemosiderosis will develop as a result of chronic hemolytic anemias even though the fishes themselves do not show any apparent abnormality, also that phenol can be one of the causes of such hemosiderosis.