With the recent advent of improved analytical and biomarker detection capabilities, a variety of organic chemicals have been found in trace amounts (Trace Organic Chemicals, TOrCs) in surface waters and fish tissue. TOrCs include pharmaceuticals, personal care products, surfactants, pesticides, flame retardants, and other organic chemicals, some with unknown modes of action or effects. Identifying or predicting ecological effects of TOrCs in typical aquatic multi-stressor situations is challenging, requiring a variety of epidemiological tools that together, can diagnose effects at multiple scales of ecological organization. Five objectives were addressed in this research: (1) develop and apply a procedure to prioritize which TOrCs are of most concern; (2) develop and test a conceptual site screening framework; (3) evaluate and test diagnostic approaches to identify potential risks due to TOrCs using various case studies; (4) develop a relational database and user interface with which the water resource community can enter, store, and search TOrC exposure data in the U.S.; and (5) foster partnerships and transfer knowledge gained in this research to the water quality community. TOrC fate, effects, and occurrence data were compiled in a database for over 500 organic chemicals based on over 100 published studies representing more than 50 organizations and 700 sites. Alternative risk-based prioritization processes and draft lists of high priority TOrCs were developed. A preliminary site screening and diagnostic framework was developed and evaluated using seven different case study sites. EPA's causal analysis (stressor identification) procedures, Canada's Environmental Effects Monitoring (EEM) procedure, the ecosystem model CASM (Comprehensive Aquatic System Model), and several other specialized diagnostic tools were used and evaluated. A relational database based on Tetra Tech's EDAS2 was developed using the Microsoft platform. The modified version of EDAS2, built on the EPA WQX data model, provides web-based data queries using a combination of tabular data for downloads and a visual map interface that allows the user to view, query, and select sites from the map having chemical or biological data. The database is not discussed in this report but can be accessed through WERF. This Final Report summarizes all other approaches used and results obtained in this research, discusses critical data gaps and other important uncertainties, and provides testable hypotheses and recommendations for Phase 2 testing and analyses.

This project evaluated the quality of data needed to determine relationships between chronic Whole Effluent Toxicity (WET) test results and in-stream biological condition. A data quality objectives approach was used, which included several proposed measurement quality objectives (MQOs) that specified desired precision, bias, and sensitivity of methods used. Six facilities (four eastern and two western U.S.) participated in this study, all having design effluent concentrations > 60% of the stream flow. In accordance with a Quality Assurance Project Plan most of the facilities completed four quarters of chronic Ceriodaphnia dubia, and Pimephales promelas (fathead minnow) WET tests, and three quarters of Selenastrum capricornutum (green algae) WET testing following the most recent USEPA methods. Several other WET tests were conducted to address MQOs including splits, duplicates, and blind positive and negative controls. Macroinvertebrate, fish, and periphyton bioassessments were conducted at multiple locations up and downstream of each facility following the most recent USEPA Office of Water bioassessment protocols. Test acceptance criteria were met for most WET tests, however, this study demonstrated the need to incorporate other MQOs in a full study (such as minimum and maximum percent significant differences and performance on blind samples) to ensure accurate interpretation of effluent toxicity. More false positives, lower test endpoint (i.e., higher toxicity), and more "failed" (non-compliant) tests were observed using No Observed Effect Concentrations (NOEC) as compared to IC25s (concentration causing >= 25% decrease in organism response compared to controls). Algae tests often yielded the most effluent toxicity in this study, however, this test was most susceptible to false positives and high inter-laboratory variability. WET test results exhibited few relationships with bioassessment results, even when incorporating actual effluent dilution. Neither frequency of WET non-compliance nor magnitude of WET were clearly related to differences in biological condition up and downstream of a discharge for the most part. Macroinvertebrate assessments were most able to discriminate small changes downstream of the effluent, followed by periphyton and then fish. The sampling methods used were robust but a full study should collect more field replicates up and downstream of each discharge to increase detection power. Macroinvertebrate and periphyton assessments together appeared to be sufficient to address project objectives. Fish assessments could be useful as well but would entail more effort and cost per site than expended in this project, to be useful.

Under the National Pollution Discharge Elimination System (NPDES), many municipal and industrial wastewater treatment facilities must perform Whole Effluent Toxicity (WET) Testing. Regulatory agencies determine the level of compliance of each facility by making inferences about the results of these tests. There has been some concern regarding appropriate ways to integrate WET tests into NPDES permits. The central issue of this concern involves determining the relationship between WET tests and instream biological conditions. Previous research (WERF project 95-HHE-1) has examined this issue using historical data. Because of issues with data comparability, i.e. questionable data quality, and project design, results were inconclusive. This study plan was designed to collect new data on method performance for both WET and bioassessment that would help answer the outstanding question. The study plan was designed using a Data Quality Objective (DQO) approach in which DQOs and MQOs were defined. These DQOs and MQOs were characterized using technical input from many scientists from federal, state, and private organizations. It was through this effort that certain technical design issues arose that needed further investigation before implementing the definitive study. Among these issues were determining if DQOs and MQOs were achievable, and determining appropriate biological assessment methods for various ecoregions (e.g. effluent dependent streams in the arid west). In order to appropriately address these issues, it was determined that a pilot study would be implemented before the definitive study. The pilot study is designed as a one-year study in which participating facilities will perform quarterly WET tests (Ceriodaphnia, P. promelas, Selenastrum) and at least one bioassessment (macroinvertebrate, fish, algae) as well as providing other prescribed data requirements. Results of the pilot will provide answers to technique design issues and will ultimately determine the most appropriate study design for the definitive study.