Receiving water environmental effects associated with discharges from Ontario pulp mills

We examined the receiving areas of 10 Canadian pulp mills, including kraft mills using chlorine, as well as sulphite mills, which discharged >40,000 m³ day^-1 of effluent. Field collections included sampling of receiving water for chemistry and toxicity testing, and sampling of local fish for organ weights, MFO activity and plasma steroid levels, and levels of liver dioxins. Although white sucker collected near bleached kraft mills exhibited the highest EROD induction and levels of dioxins, elevated enzyme activity was observed in fish from sites which did not use chlorine. Decreased circulating levels of sex steroids, decreased gonadal size and increased liver size were observed in fish collected at sites without chlorine bleaching and at sites with secondary treatment of effluent.