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Abstract
Alkylphenol ethoxylates (APEs) are widely used surfactants in domestic and industrial
products, which are commonly found in wastewater discharges and in sewage treatment
plant (STP) effluents. Degradation of APEs in wastewater treatment plants or in the
environment generates more persistent shorter-chain APEs and alkylphenols (APs) such
as nonylphenol (NP), octylphenol (OP) and AP mono- to triethoxylates (NPE1, NPE2 and
NPE3). There is concern that APE metabolites (NP, OP, NPE1-3) can mimic natural hormones
and that the levels present in the environment may be sufficient to disrupt endocrine
function in wildlife and humans. The physicochemical properties of the APE metabolites
(NP, NPE1-4, OP, OPE1-4), in particular the high K(ow) values, indicate that they
will partition effectively into sediments following discharge from STPs. The aqueous
solubility data for the APE metabolites indicate that the concentration in water combined
with the high partition coefficients will provide a significant reservoir (load) in
various environmental compartments. Data from studies conducted in many regions across
the world have shown significant levels in samples of every environmental compartment
examined. In the US, levels of NP in air ranged from 0.01 to 81 ng/m3, with seasonal
trends observed. Concentrations of APE metabolites in treated wastewater effluents
in the US ranged from < 0.1 to 369 microg/l, in Spain they were between 6 and 343
microg/l and concentrations up to 330 microg/l were found in the UK. Levels in sediments
reflected the high partition coefficients with concentrations reported ranging from
< 0.1 to 13,700 microg/kg for sediments in the US. Fish in the UK were found to contain
up to 0.8 microg/kg NP in muscle tissue. APEs degraded faster in the water column
than in sediment. Aerobic conditions facilitate easier further biotransformation of
APE metabolites than anaerobic conditions.