Methyl ester of fatty acids, Cx-Cy, Hydroxymethylated

Toxicity to microorganisms

Description of key information

The 3 hr. EC50 value for activated sludge respiration inhibition was determined to be > 1,000 mg/L; which was the highest concentration evaluated.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

Additional information

The effect of Methyl(Polyhydroxymethyl)Stearate on activated sludge microorganisms maintained in an aerobic environment was assessed by the Activated Sludge Respiration Inhibition Test Method (OECD 209). The test contained control, reference and treatment groups. The control replicates were used to determine the background respiration rate of the sludge and were not dose with the test or reference substance. The reference group was dosed with 3,5-dichlorophenol, a known inhibitor of respiration, at concentrations of 3, 15 and 50 mg/L. Treatment groups were dosed with Methyl(Polyhydroxymethyl)Stearate at concentrations of 10, 30, 100, 300 and 1000 mg/L. After an exposure period of three hours, the respiration rates of the test solutions were measured using a YSI Model 50B-115 Dissolved Oxygen Meter. The respiration rates in the two controls were 46.5 and 48.0 mg O2/L/hr. The difference between the two control respiration rates were approximately 3%, and was within the 15% difference limit established for the test. The validity of the test was further supported by the results from the 3,5- dichlorophenol reference group, which resulted in an EC50 of 10.7 mg/L. The EC50 for the reference substance was within the 5 mg/L to 30 mg/L range considered acceptable for the test. A dose response curve was not observed for the treatment group. The EC50 value for Methyl(Polyhydroxymethyl)Stearate is therefore greater than 1000 mg/L, the highest concentration tested.