Status of the WET Program William Telliard Director, Analytical Methods USEPA Office of Science & Technology Office of Water

What is WET? — Whole effluent toxicity (or WET) is defined as the combined toxic effect of an effluent measured directly by an aquatic toxicity test — WET is one of three components of EPA’s integrated approach to water quality-based toxics control — 17 WET test procedures using plants, fish, and invertebrates are promulgated at 40 CFR Part 136

Office of Water Background — WET Methods Rule Promulgated - Whole effluent toxicity (WET) test methods were promulgated at 40 CFR Part 136 on 10/26/95 for use in monitoring water quality, controlling toxic discharges, and protecting aquatic life in receiving waters (60 FR 53529) — WET Methods Rule Challenged - 6 different litigants sued EPA in 5 different courts of appeal — Resulted in Settlement Agreements - Law suits were settled by 3 different settlement agreements United Water Florida, City of Washington, City of San Bernadino Lone Star Steel Edison Electric Institute, Western Coalition of Arid States, et al. (EEI/WestCAS)

Office of Water Settlement Agreement Requirements — In a 7/24/98 settlement agreement with Edison Electric Institute, et al., EPA agreed to:  Publish technical correction notice (completed 2/99)  Publish analytical variability guidance (completed 6/00)  Publish method guidance document (completed 7/00)  Conduct WET Interlaboratory Variability Study (the WET Study) (completed 4/00)  Publish table of method variability measurements (CVs) (completed 9/01)  Propose method changes (proposed 9/01; final rule to be completed by 11/08/02)  Propose to ratify or withdraw methods (proposed 9/01; final rule to be completed by 11/08/02)

Office of Water Technical Correction Notice — Errata for the Effluent and Receiving Water Toxicity Testing Manuals - EPA 600/R-98/182 — Corrects technical errors and omissions in WET method manuals — Available at: http// — This errata will soon be unnecessary, when EPA publishes new method manual editions in November

Office of Water Guidance Documents — Method Guidance Document Method Guidance and Recommendations for Whole Effluent Toxicity (WET) Testing (40 CFR Part 136) – EPA 821/B-00/004 — Provides Guidance on: Nominal error rates Confidence intervals Concentration-response relationships Dilution series selection Dilution waters — Available at: http//

Office of Water Guidance Documents — Variability Guidance Document Understanding and Accounting for Method Variability in Whole Effluent Toxicity Applications Under the National Pollutant Discharge Elimination System Program – EPA 833/R-00/003 — Provides guidance to regulatory authorities, permittees, and testing labs on how to understand and account for measurement variability in WET testing — Available at: http//

Office of Water September 28, 2001 Proposed Rule — On September 28, 2001, EPA published a proposed rule to revise and ratify WET test methods — Proposed rule fulfills requirements of two WET settlement agreements — Summary of proposed rule Method revisions - incorporates revisions to address specific stakeholder concerns Interlaboratory Variability Study - summarizes results from EPA’s WET Interlaboratory Variability Study Ratification/withdrawal - ratifies or withdraws WET test methods based on results from the WET Interlaboratory Variability Study

Office of Water Method Revisions — Correct minor technical errors — Update methods with newly collected method precision data — Address specific stakeholder concerns blocking by known parentage pH drift concentration-response relationships dilution series dilution waters pathogen interference

Office of Water WET Interlaboratory Variability Study — Largest most comprehensive study of whole effluent toxicity test methods to date Test methods -12 of the 17 approved WET test methods evaluated in the study Laboratories - 56 different laboratories involved, each in an average of 3 methods Samples - over 700 samples analyzed Sample types - effluents, receiving waters, blanks, and reference toxicants — Study data summarized in proposed rule to support ratification of WET methods

Office of Water Ratification/Withdrawal — 11 of 12 methods evaluated in the WET Study were proposed for ratification Ratification means that EPA reaffirms its previous approval of these methods for use in National Pollutant Discharge Elimination System (NPDES) monitoring and compliance — 1 method (Holmesimysis costata acute method) was proposed for withdrawal and reproposal WET Study results revealed that this test procedure, which was designed for a related species (Mysidopsis bahia), is inadequate for the Holmesimysis costata test species

Office of Water Current Status — EPA received public comment on the proposed rule through January 11, 2002 EPA received 38 comment packages from the following groups: – Laboratories; POTWs; Regulatory authorities; Industries; Industry or trade associations; Environmental companies representing POTWs or industry — EPA plans to take final action on the proposed rule by November 2002 — New editions of each of the 3 WET method manuals are expected by November 2002