The pulp and paper mill are one of the highly polluting industries and hence the study of the effects of effluent exposure on organisms, populations or communities has high ecological relevance. The presents study uses the fingerlings of common carp, Cyprinus carpio, to analyse the effects of paper mill effluents on liver architecture at 7, 14, 21 and 28 days of exposure using light microscopic study and haematoxylin-Eosine stain. We present a survey on toxic effects, proposing a sequence of exposure duration dependent effects. Hepatocytes showed various anomalies such as vaculation, pycnotic nucleus, karyolysis, karyohexis, leucocyte infiltration, necrotic area, amongst others. We concluded that the paper mill effluent is extremely toxic to fish, even in a very low concentration. Such contaminant renders fish health by affecting them physiologically and ultimately subject to mortality thereby distressing the aquatic biota.
