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Long-term toxicity to aquatic invertebrates

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The test substance is poorly soluble and made of constituents with various water solubilities. As a consequence, exposures were performed with Water Accomodated Fractions (WAFs). Therefore, the results are based on nominal loadings and no NOEC value can be given.
Results of computer modelling to estimate chronicity in a 21-day freshwater invertebrate study, based on reproduction, show that this substance will not produce toxicity at or below its maximum attainable water solubility.

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The aquatic toxicity of was estimated using the Petrotox computer model, which combines a partitioning model used to calculate the aqueous concentration of hydrocarbon components as a function of substance loading 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 partitioning coefficients (KMW) that describe the partitioning of the hydrocarbons between the water and organism. Results of computer modelling to estimate chronicity in a 21-day freshwater invertebrate study, based on reproduction, show that this substance will not produce toxicity at or below its maximum attainable water solubility.

Morover, two studies on long term toxicity to aquatic invertebrates were available and confirm the calculated result from Petrotox.. One study, dealing with the toxicity of "Hydrocarbons, C14 -C17, n-alkanes, <2% aromatics" on Ceriodaphnia dubia was considered unassignable because the concentrations were expressed only as "% WAF" (WAF = 1 V substance + 10 V dilution water). However, the NOELR was 100% WAF. A second study with Ceriodaphnia dubia exposed to "Hydrocarbons, C14-C17, n-alkanes, <2% aromatics" found that no toxic effect was obtained with 100% WAF corresponding to 70 mg/L (Dufresne, 2001b).