C8-C26 branched and linear hydrocarbons – Distillates

Sediment toxicity

Description of key information

OECD 225:
- NOEC (28d): 100 mg/kg sediment dw test mat. (nominal) based on: mortality;
- EC50(28d): 590 mg/kg sediment dw test mat. (nominal) based on: mortalilty.
OECD 218:
- NOEC (28d): ≥1000 mg/kg sediment dw test mat. (nominal) based on: Emergence rate and adult mortality;
- EC50 (28d): >1000 mg/kg sediment dw test mat. (nominal) based on: Emergence rate and adult mortality.

Additional information

A test was performed with the sediment organism Lumbriculus variegatus. 40-60 worms of Lumbriculus variegatus were exposed to formulated spiked sediment at nominal ‘dry weight’ concentrations of 10, 32, 100, 320 and 1000 mg/kg sediment. The study was carried out according to OECD test guideline 225 and in compliance with GLP. Analytical monitoring was performed, however analysis of ‘wet’ sediment was problematic, therefore measurements with sediment that was ‘pre-dried’ prior to analysis were also carried out.

Analysis of the pre-dried sediment at nominal concentrations of 100, 320 and 1000 mg/kg dw sediment (dried at 60°C for approximately 24 hours) gave measured concentrations of 68% to 78% of nominal and from 28% to 38% nominal on days -9 and 0, respectively. Analysis of the 1000 mg/kg ‘dry’ sediment on Day 28 showed a measured concentration of 51% of nominal. Results for the 10 and 32 mg/kg dw sediment test concentrations were variable since these were close to or below the limit of quantitation of the analytical method. The low recovery rates can be attributed to the difficult nature of the test substance; losses may have occurred due to volatilisation during media preparation, or due to non-extractable residues bound to the sediment phase.

Analysis of the overlying water on Days 0 and 28 gave measured concentrations less than the limit of quantitation of the analytical method. Results for the interstitial pore water were below the limit of quantitation on Days 0 and 28 at 10 mg/kg dw sediment and on Day 0 at 1000 mg/kg dw sediment. A measured interstitial pore water concentration of 7.1 mg/l was determined at 1000 mg/kg dw sediment on Day 28.

Based on survival, the 28-day EC₅₀was determined to be 590 mg/kg dw sediment, and the NOEC was 100 mg/kg dw sediment. There were no significant differences in body weight compared to controls at any test concentration.

The toxicity of a sample of GTL Gasoil Distillates has also been determined by Harlan Laboratories (Goodband and Mullee, 2011) in a test with the sediment organism Chironomus tentans. The test was conducted in accordance with OECD Test Guideline 218.

Chironomus tentans were exposed to formulated spiked sediment nominal loading rates of 1000 mg/kg of test material over a period of 28 days, following a range finding test where no effects were recorded at 1000 mg/kg. The study was carried out according to GLP and analytical monitoring was performed. Analytical work on the ‘wet’ sediment was problematic, therefore analysis on the ‘dry’ sediment and wet sediment ‘pre-dried’ before analysis sediment was also carried out.

The test results, expressed as the EC₅₀and NOEC values, showed that the sample was not toxic to sediment organisms at 1000 mg/kg over the time period tested.

Analysis of the ‘dry’ sediment on the day of preparation (Day -7) showed measured concentrations to be 93% of nominal. Analysis of the ‘pre-dried’ sediment showed the measured concentrations to be stable for the duration of the study. Analysis of the overlying and interstitial pore water on Days 0 and 28 gave measured concentrations below the limit of quantitation of the analytical method.

It should be noted that the tests were designed to evaluate the toxicity of single substances and not complex mixtures such as the test item 'Distillates (Fischer-Tropsch), C8-26-branched and linear' which is considered as an UVCB substance. This means that greater care should be taken in the interpretation of the data (see attached CSR for more details).