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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Of all the tested components of the reaction mass of phenol and 4,4’-isopropylidenediphenol , Bisphenol A was most toxic to algae.  In a 96 hour test with the saltwater algae, Skeletonema costatum, the EyC10 and EyC50 (based on cell number) for Bisphenol A was determined to be 0.4 mg/L and 1 mg/L, respectively.  Furthermore, in a 96 hour test with the freshwater algae, Psedokirchnerella subcapitata, the EyC10 and the EyC50 (based on cell number) for Bisphenol A was determined to be 1.36 mg/L and 2.73 mg/L, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:
2.73 mg/L
EC50 for marine water algae:
1 mg/L
EC10 or NOEC for freshwater algae:
1.36 mg/L
EC10 or NOEC for marine water algae:
0.4 mg/L

Additional information

 One 72-hour algal study with Desmodesmus subspicatus was available for 2-acetone, polymer with phenol (a mixture of some of the major and minor components of the reaction mass of phenol and 4,4’-isopropylidenediphenol). This study was deemed reliable for use in risk assessments (Klimish score = 1). The 72-hour ErC10 and ErC50 values (based on growth rate) for 2-acetone, polymer with phenol are 10.3 mg/L and >100 mg/L, respectively. From the same study, the 72-hour EyC10 and EyC50 values (based on cell number) for 2-acetone, polymer with phenol were determined to be 2.7 mg/L and 15.6 mg/L, respectively. Algal toxicity tests with the two major components of the reaction mass, phenol and 4,4’-isopropylidenediphenol (a.k.a Bisphenol A), were also available. In a valid toxicity study (Klimish score = 2) with the freshwater algae, Psedokirchnerella subcapitata,the 96-hour EyC50 (cell number) for phenol was determined to be 61.1 mg/L. In a valid toxicity study (Klimish score = 2) with the saltwater algae, Skeletonema costatum, the 96-hour EyC10 and EyC50 values for Bisphenol A (based on yield, or cell number) were determined to be 0.4 mg/L and 1.0 mg/L, respectively. In a valid toxicity study (Klimish = 1) with the freshwater algae,Psedokirchnerella subcapitata, the 96-hour EyC10 and EyC50 values for Bisphenol A (based on yield, or cell number) were determined to be 1.36 mg/L and 2.73 mg/L, respectively.  

 

Bisphenol A was the most toxic component of the reaction mass of phenol and 4,4’-isopropylidenediphenol based on EyC50 values. The growth rate endpoint is preferred over the cell number (yield) endpoint according to ECHA guidance (Chapter R.7B). However, only one available study reported a growth rate endpoint, and the raw data for the other studies was not readily available in order to calculate the ErC50 based on growth rate. Since the EyC50, based on yield, is generally a lower, more conservative value than the growth rate, the studies reporting the lowest EyC50 values of 1.0 mg/L and 2.7 mg/L Bisphenol A determined using the saltwater algae, Skeletonema costatum, and the freshwater algae, Psedokirchnerella subcapitata, respectively, are reported as the key studies for this endpoint.