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Registration Dossier
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EC number: 293-261-7 | CAS number: 91052-99-2 A complex combination of hydrocarbons obtained from distillation of the butadiene-free C4 fraction of a naphtha steam-cracking process. It consists predominantly of branched olefinic hydrocarbons having carbon numbers of C8, C12, C16 and C20 and boiling in the range of approximately 105°C to 120°C (221°F to 248°F).
Endpoint summary
Administrative data
Description of key information
Experimental data was available for some category streams and endpoints. Key findings are summarised below:
For short-term toxicity to fish, toxicity data was available for tetrabutene (C16) (Infracor (Speikamp), 2002), which reported the 96 hour fish LC50 to be >1.55 mg/L, that is, above the highest saturation concentration.
For short-term toxicity to aquatic invertebrates, two studies were available for the stream Dodecene, branched (CAS97280 -83 -6), predominant carbon number of C12. Huntingdon Life Sciences (2009a) report that due to the low solubility of the test substance a WAF method was used to prepare the stock solution. The 48 hour EC50 was determined to be > 100 mg/L WAF. The second study, Infracor (2000), provided no detail on how the stock solution was prepared, however the exposure concentrations were confirmed by analysis at the start and end of the test. The highest exposure concentration which could be produced was 3.1 mg/L (geometric mean). No effects were observed at any test concentrations, so the 48 hour EC50 was therefore determined to be > 3.1 mg/L.
For toxicity to aquatic algae, two studies were available for streams in this category: Dodecene (CAS 97280-83-6, branched predominant carbon number of C12) and Polybutene (CAS 9003-29-6, predominant carbon number of C16). Huntingdon Life Sciences (2009b) report that due to the low solubility of dodecene, branched a WAF method was used to prepare the stock solution. The 72 hour EC50 was determined to be > 100 mg/L WAF and the NOEC was 100 mg/L WAF. Dr. U. Noack-Labortorien (2009) also used a WAF method was used to prepare the stock solution of butene, homopolymer due to the low solubility of the test substance. The 72 hour EC50 was determined to be > 19.2 mg/L and the NOEC was 19.2 mg/L.
For toxicity to aquatic microorganisms, 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 the absence of experimental data for other streams in this category, ECOSAR modelling was used as key study to predict, for each endpoint, the LC50 values of six representative Category B constituents and one representative read-across molecule, ranging from C8 to C20. The predicted EC50/LC50 values for different organisms ranged from 0.0000233 to 1.419 mg/L, while Chronic Values (ChV) ranged from 0.0000053 to 0.570 mg/L. Fish and aquatic invertebrates were found to be equally sensitive to Category B constituents, showing more sensitivity than algae.
In addition to the experimental and ECOSAR data, the aquatic toxicity of the main Category B constituents (C8, C12, C16 and C20 iso-olefins) was predicted by a QSAR, the PETROTOX v4..0 computer model. PETORTOX is a well-documented and peer reviewed model that is widely used across the chemicals industry. The substances of this category fit within the criteria of the model and there are no reservations about the validity of the model runs. The predicted LL50/EL50 values for aquatic species ranged from 2.18 to >1000 mg/L. The predicted EL10 values for aquatic species ranged from 0.568 to >1000 mg/L.
Additional information
ECOSAR for representative constituents of Category B and read-across molecules:
The 96 hour LC50 values for fish range from 0.0000233 to 1.252 mg/L.
The ChV values for fish range from 0.0000053 to 0.153 mg/L.
The 48 hour LC50 values for aquatic invertebrates range from 0.0000271 to 0.861 mg/L.
The ChV values for aquatic invertebrates range from 0.0000196 to 1.143 mg/L.
The 72 hour Er50 values for algae range from 0.000396 to 1.419 mg/L.
The 72 hour ChV values for algae range from 0.000514 to 0.570 mg/L.
PETROTOX for main carbon blocks Category B (C8, C12, C16 and C20 iso-olefins):
The predicted LL50 values for Oncorhynchus mykiss ranged from 2.97 to >1000 mg/L.
The predicted EL10 values for Oncorhynchus mykiss ranged from 0.568 to >1000 mg/L
The predicted EL50 values for Daphnia magna ranged from 5.18 to >1000 mg/L.
The predicted EL10 values for Daphnia magna ranged from 0.992 to >1000 mg/L.
The predicted EL50 values for Pseudokirchneriella subcapitata ranged from 2.18 to >1000 mg/L.
The predicted EL10 values for Pseudokirchneriella subcapitata ranged from 0.418 to >1000 mg/L
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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