Within the last decade, several pesticides and toxic substances have been identified as "environmental antiandrogens" which are of sufficient potency to induce hypospadias and ambiguous genitalia in rats. Although environmental chemicals with androgenic activity had not previously been detected, it is now evident that there are "environmental androgens". Three independent research groups have detected androgenic activity in paper mill effluent (PME) [69-71]. Two groups have found that kraft mill effluent (KME) from sites on the Fenholloway river in Florida, which contain masculinized female fish (Gambusia holbrooki), contains a chemical mixture that binds AR and induces androgen-dependent
(but not glucocorticoid-dependent) gene expression in vitro. Water samples collected from three sites downstream from the discharge point of the PME all display androgenic activity while, in contrast, water samples upstream of the plant or from a nearby river do not display androgenicity. Female mosquito fish from the contaminated sites display an anal fin that is enlarged into a male-like gonopodium [72-74]. Masculinization can also be achieved in female mosquito fish and killifish in the laboratory with exposures to KME and from microbial (Mycobacterium smegmata) metabolites of phytosterols present in the KME . Similar in vivo and in vitro responses have been reported from a paper mill on Jackfish Bay, Lake Ontario, by another group of investigators. Using cytosolic preparations of fish testes, gonad, and brain, this group found substances in PME that bound AR and they also identified this activity in PME constituents (b sitosterol, flavonol, and flavone) . In addition, male and female white sucker fish (Catostomus commersoni) exposed to effluent in the field displayed a variety of reproductive effects, including an increase in size and number of reproductive tubercles, which are an androgen-dependent sex trait of males.
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