Book excerpt: The book summarizes and reviews the environmental and human safety of two classes of nonionic surfactants-alcohol ethoxylates (AE) and alkylphenol ethoxylates (APE). This unique resource contains critical data from published sources as well as from unpublished studies submitted by Soap and Detergent Association member companies. It reviews information on product chemistry and analysis, biodegradation, environmental levels (including fate and distribution), aquatic toxicity, and human safety. Recently developed analytical techniques for the extraction, separation, detection, and measurement of nonionic surfactants and their metabolites in environmental samples are described. Results of biodegradation studies performed with a variety of test systems are tabulated, as are results of field studies at wastewater treatment plants. Reported comparisons of environmental levels with results of acute and chronic aquatic toxicity tests are provided. The information on the toxicity and irritation potential of AE and APE surfactants includes data from in vitro, mammalian, and human studies.