Reaction mass of Benzene sulfonic acid, hexadecyl(sulfophenoxy)-,disodium salt and Benzene sulfonic acid, - oxibis[hexadecyl]-, disodium salt

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 72 h ErC50 for growth rate of DOWFAX 8390 -D surfactant tested with algae S. capricornutum was >100 mg/L. The No Observed Effect Concentration (NOEC) for growth rate reduction was 10.0 mg/l.

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

EC10 or NOEC for freshwater algae:

10 mg/L

Additional information

DOWFAX 8390-D surfactant is the dry form of a diphenyloxide based anionic surfactant which consists of disodium according to OECD Guideline No. 201. The cells of S. capricornutum were exposed to triplicate samples of an aqueous nutrient solution (aprox. 50 ml) containing 10, 18, 32, 56 and 100 mg/l of the test material over a period of 72 hours. Additional 6 parallel samples were included as blank controls without addition of the test substance. Furthermore, one sample with the highest test substance concentration without algae was incubated. Samples of the algae suspensions were taken at 24, 48 and 72 hours and the cell number was determined by turbidity measurements using a spectrophotometer. The area under the growth curve and the growth rates were used as a base for the calculation of the concentration leading to 50 % growth inhibition: EbC50 and ErC50 referring to the area under the growrth curve (biomass) and to the growth rate, respectively. The nominal effective 72 -hour EbC50 of DOWFAX 8390 -D surfactant tested with S. capricornutum was 42 mg/l (95 % confidence interval 30 - 68 mg/l). The EC50 value for growth rate reduction (ErC50: 0 -72h) was >100 mg/L which was the highest concentrations assayed. The No Observed Effect Concentration (NOEC) for growth rate reduction and inhibition of biomass formation was 10.0 and < 10.0 mg/l, respectively.