Risk assessment of nonylphenol and its ethoxylates in U.S. river water and sediment

A comprehensive program addressing the risks of nonylphenol (NP) and its ethoxylates (NPE) in aquatic environments of the United States has been undertaken by the Alkyl Phenol Ethoxylates Panel of the Chemical Manufacturers Association cooperating with EPA. Several hundred million pounds of NPE surfactants are used in the US each year. Nonylphenol can be an intermediate product of degradation of nonylphenol ethoxylates. A survey of those river reaches most likely to contain NPE and NP residues was conducted based on a random sample of a subset of the EPA River Reach File defined by certain selection criteria. Applying enhanced analytical techniques, little or no NP and NPE were found in river water at most locations, while low levels were usually detected in sediment. Acute and chronic toxicity tests using a variety of organisms have also been completed. New results are presented for shrimp, fish, tadpoles, midges, and algae. The risk of NP to the aquatic environment is examined by comparison of observed levels with toxicity benchmarks, and by application of equilibrium partitioning theory to calculate sediment interstitial chemical concentrations.