Long-term effects of bleached kraft mill effluents on red and white blood cell status, ion balance, and vertebral structure in fish.

In a laboratory investigation fourhorn sculpin (Myoxocephalus quadricornis) were exposed for 5-9 months to wastewater from pine and birch lines from a bleached kraft pulp plant. This long-term exposure to bleached kraft mill effluent (BKME) affected the hematology, the ion balance, and the vertebral structure. Decreased values for hematocrit and hemoglobin and a reduced red blood cell count, as well as increased levels of methemoglobin, indicated disturbances in the red blood cell status. The white blood cell picture was not significantly affected by the BKME exposure. Decreased levels of potassium and chloride ions in the blood plasma in some of the exposed fish suggest an impaired ability to maintain ion homeostasis. Elevated frequencies of vertebral deformations in fish exposed to BKME confirm previous observations of vertebral damage in feral fourhorn sculpin caught in the receiving body of water of the same bleached kraft pulp industry. Many of the parameters analyzed in this investigation may be used as health indicators in future laboratory and field studies on fish exposed to BKME.