the polymer) have received a great deal of attention lately because their breakdown products have been identified as potential hormone disruptors (U.S. EPA, 1997). Extremely low concentrations of these compounds have been shown to cause hormonal changes in fish; effects on humans are not yet established. Most types of household and industrial detergents contain a mixture of such compounds, with n values ranging from 1 to at least 18 and perhaps higher (Ahel et al., 1994b). Although the detergent molecules themselves are thought to be relatively innocuous, waste treatment breaks them down to smaller AP(nEO) compounds (almost all with n equal to 1 or 2), alkylphenols (APs), and alkylphenylpolyethoxycarboxylates (AP(nEC)s), which are more toxic than the parent compounds (Ahel et al., 1994b).

Over the last two decades, Giger and various colleagues have extensively studied the fate of the detergent compounds and their metabolites in wastewater treatment systems and downstream (e.g., Ahel et al., 1994a, 1994b, 1996; Field et al., 1995; Giger et al., 1981, 1984). Detergent break-