Uptake and metabolism of technical nonylphenol and its brominated analogues in the roach (Rutilus rutilus)

Alkylphenols have been implicated as one of the causative agents of oestrogenic contamination in fish. This study reports the fate of a technical mixture of secondary and tertiary isomers of the environmental contaminant 4-nonylphenol (NP) in mature female roach. Fish were exposed to a concentration of 4.9microg/l radio-labelled technical NP over a 4-day period in a flow-through aquarium. NP residues were extracted from all tissues and analysed by reverse phase radio HPLC. The concentration of NP residues was highest in bile and liver, with apparent bioconcentration factors (apparent BCFs) of 34,121 and 605, respectively. In other tissues, apparent BCF values were recorded between 13 and 250. NP was the only residue detected in brain, muscle and blood cells whereas an additional NP derivative was detected in other soft tissues, including gonads and liver, which was identified as the brominated derivative of technical NP, dibromo-4-nonylphenol. Traces of the dibrominated NP were also detected in aquarium water but only in the presence of NP, which suggested that bromination of the NP parent compound occurred in situ in the water due to the presence of trace amounts of oxidised bromine species in municipal water following disinfection. There was no evidence of further metabolism of the brominated derivative in roach, but a single major metabolite of NP was present in liver and bile, which was identified as the glucuronide conjugate of 4-(hydroxy-nonyl)-phenol. This detection of only one NP metabolite suggests that, in contrast to other fish species, the variety of metabolic pathways available for the deactivation of 4-alkylphenols in roach is limited. This study indicates that brominated alkylphenols bioconcentrate in a range of tissues and, as they have been detected in the aquatic environment, they could contribute to the body burden of alkylphenolics in fish. The formation of these brominated derivatives in aquarium water suggest that they could confound toxicity tests to assess the effects of alkyphenols to aquatic organisms.