Potential Effects of Contaminants on Fraser River Sockeye Salmon

In recent years, vitellogenin induction has been used as an indicator <strong>of</strong> exposure toendocrine disrupting compounds that have estrogenic effects in male fish. Data fromvarious studies have shown that exposure to 17â-estradiol, alkylphenols (such as 4-nonylphenol, 4-tert-butylphenol, 4-tert-octylphenol), and alkylphenol polyethoxylates(such as nonylphenol diethoxylate,) induces vitellogen production in male fish (Joblingand Tyler 2003a; 2003b; Pait and Nelson 2002). Data from laboratory studies indicatethat male sheepshead minnows (Cyprinodon variegatus) exposed to concentrations <strong>of</strong>4-nonylphenol as low as 5.4 µg/L had significant increases in plasma vitellogenin levels(Hemmer et al. 2001). The relative potencies <strong>of</strong> selected estrogenic compounds arepresented in Table 6.1 (Jobling and Sumpter 1993). The results <strong>of</strong> field studiesconducted in the U.K. have demonstrated that vitellogenin induction is correlated withan elevated incidence <strong>of</strong> intersex (i.e., the simultaneous presence <strong>of</strong> both male andfemale gonadal characteristics in fish) and reductions in gonad size (i.e., as indicatedby reduced gonadosomatic index scores; which is the ratio <strong>of</strong> gonad weight to bodyweight), both <strong>of</strong> which can reduce reproductive success (Jobling et al. 1998).The results <strong>of</strong> laboratory studies provide a basis for identifying effectiveconcentrations <strong>of</strong> alkylphenols in water. In Japanese medaka, 90-d exposure <strong>of</strong> newlyhatched males to 50 or 100 µg/L <strong>of</strong> 4-nonylphenol resulted in increased frequency <strong>of</strong>intersex (50% and 86% <strong>of</strong> the fish developed ovotestis; Gray and Metcalfe 1997). In alife-cycle study on this species, a significantly increased incidence <strong>of</strong> intersex (asindicated by the presence <strong>of</strong> ovotestis) was observed in the progeny <strong>of</strong> fish exposed to4-nonylphenol concentrations as low as 8.2 µg/L (Yokata et al. 2001). Decreasedfertility was also observed in adults exposed to 17.6 µg/L <strong>of</strong> 4-nonylphenol.Insufficient toxicity data were located to establish toxicity thresholds for alkylphenolsor APEOs that could be applied to assess effects on Fraser River sockeye salmonassociated with exposure to this class <strong>of</strong> contaminant.Industrial Chemicals - The industrial chemicals in the Fraser River Basin that havebeen shown or are suspected <strong>of</strong> having endocrine disruption effects include APEOs,bisphenol A, phthalates, chlorophenols, PAHs, PCBs, PCDDs/PCDFs, and PBDEs(and PBBs). The estrogenic effects <strong>of</strong> APEOs were discussed in the above section onpharmaceuticals and personal care products.Bisphenol A - The results <strong>of</strong> laboratory studies show that exposure to bisphenol Acauses estrogenic effects in salmonids and other fish species. In fathead minnows,exposure to 160 µg/L <strong>of</strong> bisphenol A for >71 days results in elevated plasmavitellogenin levels in males (Sohoni et al. 2001). In the same study, egg production85