Toxicity of methyl-tert-butyl ether to freshwater organisms

Increased input of the fuel oxygenate methyl-tert-butyl ether (MTBE) into a quatic systems has led to concerns about its effect(s) on aquatic life. As part of a study conducted by University of California scientists for the St ate of California, the Aquatic Toxicology Laboratory, UC Davis, reviewed ex isting literature on toxicity of MTBE to freshwater organisms, and new info rmation was generated on chronic, developmental toxicity in fish, and poten tial toxicity of MTBE to California resident species. Depending on time of exposure and endpoint measured, MTBE is toxic to various aquatic organisms at concentrations of 57- > 1000 mg/l (invertebrates), and 388-2600 mg/l (ve rtebrates). Developmental effects in medaka (Oryzias latipes) were not obse rved at concentrations up to 480 mg/l, and all fish hatched and performed f eeding and swimming in a normal manner. Bacterial assays proved most sensit ive with toxicity to Salmonella tryphimurium measured at 7.4 mg/l within 48 h. In microalgae, decreased growth was observed at 2400 and 4800 mg/l with in 5 days. MTBE does not appear to bioaccumulate in fish and is rapidly exc reted or metabolized. Collectively, the available data suggests that at env ironmental MTBE exposure levels found in surface waters (<0.1 mg/l) this co mpound is likely not acutely toxic to aquatic life. However, more informati on is needed on chronic and sublethal effects before we can eliminate the p ossibility of risk to aquatic communities at currently detected concentrati ons. (C) 2000 Elsevier Science Ltd. All rights reserved.