2,2',6,6'-tetrabromo-4,4'-isopropylidenediphenol

Toxicity to aquatic algae and cyanobacteria

Description of key information

96 h NOEC 5.6 mg/L (Pseudokirchneriella subcapitata) 

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

5.6 mg/L

Additional information

In the key study, the potential of TBBPA to affect the freshwater algae S. capricornutum (new name Pseudokirchneriella subcapitata) was investigated in a 96 h test. 14C-TBBPA fortified with unlabelled test article was added to freshwater at nominal concentrations of 0, 0.60, 1.2, 2.4, 4.8, and 9.6 mg/L. An inoculum of S. capricornutum cells sufficient to provide 1 x 10E4 cells/mL was aseptically introduced to each vessel. Cell counts were made at 24 h intervals.

Mean measured 14C-activity indicated TBBPA concentrations averaged 61% of nominal at time 0 and 96 h, and were reported to be 0, 0.34, 0.76, 1.5, 3.0, and 5.6 mg/L (average of 0 and 96 h values). Analysis of the high dose via HPLC indicated concentrations substantially below that of radiometric value (0.55 mg/L versus 5.1 and 6.1 mg/L in the 0 and 96 h samples). The report concludes the difference was due inclusion of fine particulate matter (e.g. undissolved TBBPA) in the radiometric value, which was excluded on the HPLC column. Based on this, the report concluded the true water solubility of TBBPA was approximately 0.55 mg/L, and that all of the tested TBBPA concentrations were at or above TBBPA's water solubility.

Algal cell counts performed at 24, 48, 72 and 96 h indicated no effect of TBBPA at any dose. The 96 h NOEC in freshwater algae was ≥5.6 mg/L (measured), which was above TBBPA's water solubility.

Supporting information is provided in the form of a study in which the toxicity of the test material to three species of marine algae was investigated in test conducted in accordance with sound scientific principles. Marine unicellular algae were exposed to industrial brominated compounds in six algal growth media. The toxicity test method was similar to that of Walsh and Alexander (1980).

Skeletonema costatum, Thalassiosira pseudonana and Chlorella sp. were exposed to the test material in six salt water media for 72, 72 and 96 hours, respectively (salinity 30 parts per thousand). The test material was introduced into growth flasks by adding 0.05 mL test material in nanograde acetone to 51 mL growth medium with algae. Toxicity was expressed as the EC50 based upon cell numbers after incubation for 72 hours.

Under the conditions of the study, Chlorella sp. was not inhibited by as much as 50 % by 1.5 mg/L test material and the test material was toxic to S. costatum and T. pseudonana below the estimated saturation concentration (1.5 mg/litre).