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Short-term ecotoxicological testing data for tetramethyl bisphenol A (TMBPA; CAS# 5613-46-7) are available for all three primary trophic levels (i.e., fish, aquatic invertebrates and algae/aquatic plants) and also for microorganisms. For fish, exposure of fathead minnow, Pimephales promelas, to TMBPA resulted in a 96-h LC50 of greater than 0.76 mg a.i./L (mean measured concentration), the highest concentration tested. The 96-h No-Effect Concentration (NOEC) was 0.28 mg a.i./L (mean measured concentration). Exposure of the aquatic invertebrate, Daphnia magna, to TMBPA resulted in 24-h EC50 of 6.5 mg/L (95% confidence limit = 4.7 – 8.9 mg/L) and a 48- h EC50 of 3.1 mg/L (95% confidence limit = 2.7 – 3.5 mg/L). The 48- h NOEC was 0.48 mg/L. For the green algae, Pseudokirchneriella subcapitata, exposure to TMBPA for 72 h resulted in an EC50 of 0.37 mg/L (measured TWA; 95% confidence limit = 0.083 – 0.59 mg/L) when calculated using biomass expressed as yield and an EC50 of 0.67 mg/L (measured TWA; 95% confidence limit of 0.54 – 0.79 mg/L) when calculated using average growth rate. The 72-h NOEC value was 0.15 mg/L for both biomass expressed as yield and growth rate. Exposure of activated sludge microorganisms in primarily domestic sewage to TMBPA for 3 h resulted in an estimated EC50 value greater than 1000 mg/L. The 3-hour NOEC was determined by linear regression to be 221 mg/L  Since the 3-hour range-finding test resulted in an EC50 value greater than 1000 mg/L, a definitive test was not conducted.