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Toxicity to microorganisms

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Description of key information

Experimental data are available for the toxicity of some Category B constituents towards active sludge. The 28 day NOEC for Hydrocarbons, C4, 1,3-butadiene-free, polymd., dibutylene fraction was 100 mg/L based on nominal concentrations. The 56 day NOEC for Hydrocarbons, C4, 1,3-butadiene-free, polymd., tetraisobutylene fraction, hydrogenated was 23.5 mg/L based on nominal concentrations.

 

In addition to the experimental data, the aquatic toxicity for the main Category B constituents (C8, C12, C16 and C20 iso-olefins) was predicted by a QSAR, the PETROTOX v4.0 computer model. PETROTOX is a well-documented and peer reviewed model that is widely used across the chemicals industry. The predicted LL50 values for Activated Sludge ranged from >1000 to >1000 mg/L. The predicted EL10 values for Activated Sludge ranged from 6.23 to >1000 mg/L.

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Additional information

The PETROTOX v4.0 model combines a partitioning model used to calculate the aqueous concentration of hydrocarbon constituents with the Target Lipid Model used to calculate acute and chronic toxicity of non-polar narcotic chemicals. PETROTOX computes toxicity based on the summation of the aqueous-phase concentrations of hydrocarbon block(s) that represent a hydrocarbon substance and membrane-water partition coefficients (KMW) that describe the partitioning of the hydrocarbons between the water and organism.

 

The predicted values were:

Species Carbon No. LL50 / EL50 (mg/L) EL10 (mg/L)
Activated Sludge C8 >1000 6.23
Activated Sludge C12 >1000 >1000
Activated Sludge C16 >1000 >1000
Activated Sludge C20 >1000 >1000

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