Are metal mining effluent regulations adequate: identification of a novel bleached fish syndrome in association with iron-ore mining effluents in Labrador, Newfoundland

Abstract

Little is known about the toxicity potential of chronic exposure to low levels of contaminants, including metals in the aquatic environment. Although water quality and effluent guidelines are in place in many countries, they have essentially evolved outside of an ecotoxicological framework which requires field investigations coupled with long-term chronic toxicity studies. The potential ecotoxicological effects of heavy metals are coming under greater scrutiny and we have carried out pilot field studies in a major lake chain in Labrador receiving effluents from iron-ore processing mills. Analysis by inductively coupled plasma-mass spectrometry of heavy metal contaminants in water demonstrated a gradient of metals in the system with iron and manganese being dominant. Emphasis has been placed on studies on large lake trout and over three years of observations it has been established that the fish in the lake receiving the highest level of mine tailings is afflicted with a ‘clinically’ distinct skin bleaching syndrome in comparison with fish taken farther afield in the lake chain or outside the chain proper. Field staff have also commonly provided anecdotal evidence that the fish in the same lake are quite lethargic upon capture in comparison with fish taken in downstream lakes. More detailed studies have also now indicated that the syndrome is associated with changes in liver histology and hematology as well as the DNA oxidative damage reported earlier (Payne, J. F., Malins, D. C., Gunselman, S., Rahimtula, A., & Yeats, P. A. (1998). Marine Environmental Research, 46, 289–294). Using the weight of evidence approach it is indicated that iron-ore effluents are likely deleterious to fish. Also, since iron-ore effluents have traditionally been considered to be essentially ‘non-toxic’, field studies should be carried out at other non-ferrous metal mining sites to assess histopathological/physiological effects in fish populations. (Supported in part by the Toxic Chemicals Program, Department of Fisheries and Oceans.)