Distillates (Fischer-Tropsch), C8-26-branched and linear

Toxicity to aquatic algae and cyanobacteria

Description of key information

Two experimental studies with freshwater accomodated fractions containing an GtL-process analogue of the test substance, Shell-SMDS2-Diesel and Sasol SPD Diesel.
Test gudelines according OECD and EPA, but one test non-GLP and one QSAR estimate based on log Kow. 
References:
Peter Fisk Ass. Ltd. (2006)
Albertus & Philipps (2005)
Palmer (2001, 2001)

Additional information

Measured toxicity:

The acute toxicity of a sample of the substance (Shell SMDS-2) has been determined by Palmer (2001 and 2002) in a test with the unicellular alga Raphidocelis subcapitata. The test was conducted in accordance with OECD test guideline 201.

Water-accommodated fractions (WAF) of the sample were prepared in sealed vessels with minimum headspace by stirring for approximately 72 hours. The contents of the vessels were left to stand for 1-2 hours before drawing off the aqueous phase - the WAF - for testing. Static exposures

were then carried out in completely full, sealed vessels. The test was not subject to GLP and the test media were not analysed for stability or for exposure concentration. However in other respects it was considered to fulfill the requirements of current best practice.

The test results, expressed as EL50 values, showed that the sample was not acutely toxic at a loading rate of 1000 mg/l. Albertus and Phillips (2005) have reported results for acute toxicity tests carried out on a second sample of the substance (SASOL SPD Diesel) The algal test was carried out using a scaled-down version of the U.S. EPA algal bottle test method. The test media were water-accommodated fractions of the test sample that were prepared in sealed vessels with a small headspace according to the CONCAWE methodology for the ecotoxicological testing of petroleum products (CONCAWE report, 1993).The test results, expressed as EL50 and NOEL values, showed that the sample was not acutely toxic algae at a loading rate of 1000 mg/l.

Predicted toxicity:

The toxicity of the representative chemical components of Distillates, (Fischer-Tropsch), C8-26 - branched and linear to algae has been calculated in accordance with the methods described by Peter Fisk Associates (2006, see also 6.1.3 Summary) using QSARs for non-polar narcotics. The QSARs take the form of a generic equation:

log(LC50, EC50 or NOEC) = a log(Kow) + b

where a and b are constants equal to the slope and the intercept on the y axis of the regression equation and Kow is octanol-water partition coefficient of each component under consideration. The resulting EC50 and NOEC values have been combined with predicted exposure concentrations for the components in water-accommodated fractions prepared at a specified loading rate to determine the number of toxic units that the concentration of each component represents. The exposure concentrations were also determined using the methods described in Peter Fisk Associates, (2006). Toxic units have only been calculated for components with log Kow values that are below certain cut-off values. The

cut-off for acute toxicity is 6.4 for algae. A common cutoff value of 8.0 is applied for chronic toxicity. The rationale for applying the cut-off values is explained in the accompanying report (Peter Fisk Associates, 2006). A sum of toxic units for all components has been determined for invertebrates and algae. A sum greater than 1.0 indicates that there were sufficient dissolved concentrations of components in the water-accommodated fraction for a test species to be affected to an extent equivalent to an EL50 or NOEL. The model predicts the worst case situation with maximum dissolved concentrations, and therefore indicates greater toxicity than is typically observed in tests. It is predicted that the substance would not be acutely or

chronically toxic to algae at a loading rate of 100 mg/l.

Conclusions:

The results obtained by measurement in ecotoxicity tests show that Distillates, (Fischer-Tropsch), C8-26 - branched and linear is not acutely toxic to algae at loading rates of >100 mg/l. The acute toxicity results obtained by measurement in ecotoxicity tests, and by prediction using the methods

described in Peter Fisk Associates (2006), are consistent.

The results obtained by measurement indicate that Distillates, (Fischer-Tropsch), C8-26 - branched and linear are not acutely toxic algae at loading rates of >100 mg/l. Similarly, the toxicity predictions indicate that a 100 mg/l water-accommodated fraction of the substance would not be acutely toxic to these organisms. A NOEL of 1000 mg/l has been determined for effects of a sample of the substance on biomass and growth rate in a test

with algae. Chronic toxicity predictions also indicate that the substance would not be algae at a loading rate of 100 mg/l.

REACH Regulation Annex VII, 9.1.2, Column 2 lists specific rules for adaptation from the standard information requirements. The required study does not need to be conducted and information provided if there are mitigating factors indicating that aquatic toxicity is unlikely to occur, for instance if the substance is highly insoluble in water. The substance is essentially insoluble in water and according to data entry point 4.8 a value of 1 mg/l has been determined. This would qualify to waive from this information requirement.