Metabolites of Chlorinated Syringaldehydes in Fish Bile as Biomarkers of Exposure to Bleached Eucalypt Pulp Effluents

Metabolites of chlorinated phenolic compounds in fish bile have been found to be sensitive biomarkers of bleached pulp mill effluent exposure. Chlorinated syringaldehydes are largely unstudied chlorophenolics found in bleached hardwood effluent. Sand flathead (Platycephalus bassensis), Australian marine fish, were exposed to 100% chlorine dioxide-bleached eucalypt pulp effluent at concentrations of 0.5, 2, and 8% (v/v) for 4 days. Metabolites of 2-chlorosyringaldehyde (2-CSA), the predominant chlorophenolic in this effluent, were measured in the bile. The major metabolite was the conjugate of 2-chloro-4-hydroxy-3,5-dimethoxy-benzylalcohol (2-CB-OH), the reduced product of 2-CSA. 2-CB-OH was found in all fish exposed to diluted effluent and was concentrated in the bile over 1000 times above 2-CSA levels in the effluent. A separate experiment examined the metabolic fate of 2,6-dichlorosyringaldehyde (2,6-DCSA), which is one of the major chlorophenolics in chlorine-bleached eucalypt pulp effluent. Sand flathead were exposed to 2,6-DCSA by intraperitoneal injection at 15 mg/kg or through the water to 0.5, 2, or 8 μg/liter for 4 days. Analysis of the bile revealed the major metabolite of 2,6-DCSA to be the conjugate of 2,6-dichloro-4-hydroxy-3,5-dimethoxybenzylalcohol, which was found in all exposed fish and was concentrated in the bile over 20,000 times above 2,6-DCSA exposure levels. Results reveal that the analysis of metabolites of chlorinated syringaldehydes in fish bile can provide a biomarker of bleached hardwood effluent exposure that is sensitive to low levels of exposure, specific to certain bleaching sequences, and correlates well with exposure concentrations.