Indeno[4,5-d]-1,3-dioxin, 4,4a,5,6,7,8,9,9b-octahydro-7,7,8,9,9-pentamethyl-

Short-term toxicity to fish

Description of key information

The acute fish toxicity study according to OECD TG 203 showed an LC50 of 5.7 mg/l based on mean measured concentrations. 

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

5.7 mg/L

Additional information

A study according to OECD TG 203 was performed to assess the acute toxicity of the test material to rainbow trout (Oncorhynchus mykiss). Following a preliminary range-finding test, fish were exposed, in groups of ten, to an aqueous solution of the test material over a range of nominal test concentrations of 1.0, 1.8, 3.2, 5.6 and 10 mg/L for a period of 96 hours at a temperature of 14.3 to 15.l °C under semi-static test conditions. The test material solutions were prepared by stirring an excess (100 mg/L) of test material in dechlorinated tap water at approximately 2000 rpm at a temperature of 25 °C for 24 hours prior to removing any undissolved test material by filtration (0.2 µm) through a preconditioned filter to produce a saturated solution which had a nominal test concentration of 21 mg/L. A series of dilutions was made from this saturated solution to prepare the test series. The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 3 and 6 hours after the start of exposure and then daily throughout the test until termination after 96 hours.

The 96-Hour LC₅₀ based on nominal test concentrations was 7.1 mg/L with 95 % confidence limits of 6.3 -7.9 mg/L. Analysis of the freshly prepared test media sampled at 0, 24, 48 and 72 hours showed the measured test concentrations to range from 86 % to 102 % of the nominal values. However, a marked decline was shown from analysis of the old or expired test media sampled at 24, 48, 72 and 96 hours. The measured test concentrations were shown to range from 54 % to 74 % of nominal. The marked decline shown in the measured test concentrations of the old or expired test media was considered to be due to accumulation and/or adsorption of the test material to the tissues of the test fish. Given the marked decline shown in the measured test concentrations it was considered appropriate to calculate the results based on the time-weighted mean measured test concentrations also, in order to give a ''worst case" analysis of the data. The 96-Hour LC₅₀based on the time-weighted mean measured test concentrations was 5.7 mg/L with 95 % confidence limits of 5.1 - 6.4 mg/L.