EFFECTS OF SUBLETHAL EXPOSURE TO CHLORINE ON THE UPTAKE OF POLYCHLORINATED BIPHENYL CONGENERS BY RAINBOW-TROUT, SALMO-GAIRDNERI (RICHARDSON)

Chlorine-induced changes in fish gill histopathology and respiration may alter the uptake of co-contaminants which are accumulated by passive diffusion across gill membranes. The effect of chlorine exposure on gill histopathology, respiratory functions, and the uptake of three polychlorinated biphenyl (PCB) congeners by rainbow trout (Salmo gairdneri) were determined. Trout gill lamellar lesions occurring during a 24-h exposure to 0.04 mg/l chlorine included proliferation of mucous cells, hyperplasia of epithelial cells, clubbed lamellae, and lamellar fusion. These types of pathological changes would be expected to result in increased diffusion distances of the gill membrane and decreased functional gill surface area. Reductions in oxygen and PCB uptake efficiencies measured in concomitant exposures to chlorine and PCBs using a fish metabolic chamber were consistent with the histopathological results. Increases in trout ventilation compensated for the lowered uptake efficiencies. As a result of ventilatory compensation, there was little change in the oxygen consumption or PCB accumulation by trout throughout the exposure to chlorine. Correlations between oxygen and PCB uptake may provide a basis for estimating toxicant uptake using oxygen uptake data as the basis for extrapolation. © 1990.