Reviews of Environmental Contamination and Toxicology Volume 209

A national water quality criteria methodology was established in the United States (US) in 1985 (US Environmental Protection Agency; USEPA 1985).¹ Since then, several other methods for establishing water quality criteria have been developed around the world, incorporating recent advances in the field of aquatic toxicology using a variety of different approaches. The authors of a recent review compared existing methodologies and summarized the differences between them (see tables 4 and 5 in TenBrook et al. 2009). TenBrook et al. (2009) observed that although methods from the USEPA provided a good basis for calculating criteria, many newer methodologies added valuable procedures that could improve criteria generation. Of particular concern were cases having small data sets, for which the USEPA (1985) methodology does not allow criteria calculation and provides little guidance. In this review, we elaborate on the review of methodologies by TenBrook et al. (2009) and we propose a new methodology that combines features derived from the existing methodologies that have been determined to generate the most flexible and robust criteria. This new methodology also incorporates results from recent research in aquatic ecotoxicology and environmental risk assessment and is hereafter referred to as the University of California-Davis Methodology (UCDM).