tert-butyl methyl ether

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 96-h IC20 is 103 mg/l and the 96-h IC50 is 491 mg/l in Pseudokirchneriella subcapitata.

Key value for chemical safety assessment

EC50 for freshwater algae:

491 mg/L

EC10 or NOEC for freshwater algae:

103 mg/L

Additional information

There is limited information available from BenKinney et al. (1994), which prevents a full evaluation of the study. The test was conducted according to U.S. EPA guidelines, a WAF-method to prepare exposure solutions was used according to guidelines, and measured treatment concentrations were reported daily and found to be within 80% of nominal doses. A 96- ErC50 value of 184 mg/l was found in Pseudokirchneriella subcapitata (tested as Selenastrum capricornutum). According to the limited information available, the test is valid.

The Hüls AG study (1991c) is done according to directive 88/302/EEC; the test seems valid although the results have been presented as nominal concentrations. The measured test concentrations after 72 hours do not deviate by more than 20 % from the freshly prepared test solutions. An EbC50 and ErC50 of >800 in 72 hours (NOEC, 72 h, 470 mg/l) were found in P. subcapitata (tested as S. capricornutum).

The test by Slovnaft VÚRUP, a.s. (2005) is done according to the OECD guideline. As no analytical methods were performed (estimation of test concentration on basis of TOC) and the purity of the substance tested is not mentioned in the report, the study was given a Klimisch rating of 2 and assigned supporting. A 72-h EC50 value >900 mg/l was found and a NOEC of 489 mg/l in Desmodesmus subspicatus.

The ENSR test (1999g) is done according to ASTM guideline and seems a valid test. The 96-h IC20 is 103 mg/l and the 96-h IC50 is 491 mg/l in Psuedokirchneriella subcapitata (tested as S. capricornutum). As the IC20 value of 103 mg/l for P. subcapitata is the most critical of all studies performed in algae tests, this value will be used in the assessment.