The bioaccumulation of nonyphenol and its adverse effect on the liver of rainbow trout (Onchorynchus mykiss).

Alkylphenol polyethoxylates (APEs) are widely used as nonionic surfactants. Nonylphenol (NP), one of the derivatives of APEs, has been found in the aquatic environment in ranges from nanograms per liter to milligrams per liter. In this study, juvenile rainbow trout were exposed to 0 (control), 66, 220, or 660 micro g NP/L for up to 28 days. Fish remained healthy under NP exposures of 0, 66, and 220 micro g/L for the length of the experiment. All fish died after 4 days of exposure to 660 micro g NP/L. Time-dependent NP bioaccumulation was detected in the tissues of fish exposed to 220 micro g NP/L (P<0.05) and histopathological changes were observed in the livers of fish exposed to 220 micro g NP/L. Furthermore, an increase in the activity of glutathione-S-transferase (GST) was found in the liver of fish exposed to 220 micro g NP/L for 1 week (P<0.05). There was an increase in GST activity in the liver of fish exposed to 66 micro g NP/L but it did not occur before 2 weeks of exposure to NP. The GST activity then decreased in a time-dependent manner in treatment groups, and this decrease was lower in the livers of fish treated with 66 and 220 micro g NP/L than in control fish after 3 weeks of exposure (P<0.05). These results indicated that sublethal doses of NP were accumulating in the bodies of the fish and causing histopathological and biochemical changes in the livers of rainbow trout.