C4-C10 branched and linear hydrocarbons (light) – Naphtha

Endpoint summary

Additional information

'Naphtha (Fischer-Tropsch), light, C4 -10 - branched and linear' is a complex combination of hydrocarbons obtained from a feedstock derived from the catalytic hydrogenation of carbon monoxide (the Fischer-Tropsch Process), optionally followed by one or more of the following processes: hydrotreatment, hydroisomerization, hydrocracking. It consists predominately of branched and linear aliphatic hydrocarbons having carbon numbers in the range of C4-C10 and boiling in the range of approximately -3°C to 174°C (27 to 345.2°F).

 

There were no measured aquatic toxicity data for 'Naphtha (Fischer-Tropsch), light, C4-10 -branched and linear'. Therefore the toxicity of the representative chemical components of the substance to fish, invertebrates (Daphnia) and algae have been calculated by using QSARs for non-polar narcotics [key studies: 'Short-term toxicity to fish.001' and ‘Short-term toxicity to aquatic invertebrates.001’ and ‘Toxicity to aquatic algae and cyanobacteria.001’].

 

The following results were obtained by prediction [using the methods described in the report by Peter Fisk Associates (2006)]:

-       the substance could be acutely toxic to algae at a loading rate of 0.55 mg/l and to fish and invertebrates at loading rates of 1.4 and 4.0

mg/l respectively

-       the substance has predicted chronic NOELs of 0.12 mg/l to fish and invertebrates and 0.24 mg/l to algae

 

On the one hand the predictions are consistent with different Naphtha-study results, which were reported in the environmental hazard property summary review of ‘Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear’ [by Peter Fisk Associates (2006)].

From reviewing predicted toxicity data for a typical composition and comparing this with test data for related substances it was concluded that the substance:

-       could be acutely toxic to fish and invertebrates at a concentration in the range 1-10 mg/l and to algae at a concentration in the range 0.1-

1.0 mg/l

-       could be chronically toxic to fish, invertebrates and algae at concentrations in the range 0.1-1.0 mg/l.

 

On the other hand the predicted results are consistent with studies from the IUCLID dataset (2000) of ‘Naphtha (petroleum), light alkylate’ (CAS 64741-66-8), which is a near analogue to 'Naphtha (Fischer-Tropsch), light, C4 -10 - branched and linear' [weight of evidence]:

 

1) Acute toxicity of 'Alkylate naphtha' to aquatic invertebrates; based on the missing identifier "CAS number" in the IUCLID dataset the substance identity was not clear - there are two possibilities:

a) Naphtha (petroleum), heavy alkylate [CAS No. 64741-65-7], which is defined as: 'A complex combination of hydrocarbons produced by distillation of the reaction products of isobutane with monoolefinic hydrocarbons usually ranging in carbon numbers from C3 to C5. It consists of predominantly branched chain saturated hydrocarbons having carbon numbers predominantly in the range of C9 through C12 and boiling in the range of approximately 150°C to 220°C (302°F to 428°F).' --> test substance is slightly comparable to 'Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear'.

b) Naphtha (petroleum), light alkylate [CAS No. 64741-66-8], which is defined as: 'A complex combination of hydrocarbons produced by distillation of the reaction products of isobutane with monoolefinic hydrocarbons usually ranging in carbon numbers from C3 through C5. It consists of predominantly branched chain saturated hydrocarbons having carbon numbers predominantly in the range of C7 through C10 and boiling in the range of approximately 90°C to 160°C (194°F to 320°F).'  --> test substance is comparable to 'Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear'.

Result: The LC50 (48h) of the test substance 'Alkylate naphtha' to aquatic invertebrates was calculated to be 2 mg/l, the NOEC (48h) was calculated to be 0.56 mg/l; the 24h- and 96h-LC50 values were 7.9 and 4.2 mg/l respectively [weight of evidence: ‘Short-term toxicity to aquatic invertebrates.002’].

 

2) Acute toxicity of ‘Naphtha (petroleum), isomerization’ [CAS No. 64741-70-4] to aquatic invertebrates; it is defined as: 'A complex combination of hydrocarbons obtained from catalytic isomerization of straight chain paraffinic C4 through C6 hydrocarbons. It consists predominantly of saturated hydrocarbons such as isobutane, isopentane, 2,2-dimethylbutane, 2-methylpentane, and 3-methylpentane' --> the test substance is slightly comparable to 'Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear'.

Result: The EL50 (48h) of the test substance 'Naphtha (petroleum), isomerization' to aquatic invertebrates was calculated to be 10 mg/l with a 95% confidence interval of 13 to 18 mg/l. The NOEL (48h) was calculated to be 5.0 mg/l, but the observed value was 0.5 mg/l [weight of evidence: ‘Short-term toxicity to aquatic invertebrates.003’].

 

3) Toxicity of ‘Alkylate naphtha’ to aquatic plants e.g. algae; based on the missing identifier "CAS number" in the IUCLID dataset the substance identity was not clear - probably the test substance has the CAS No. 64741-70-4 and is defined as: 'A complex combination of hydrocarbons obtained from catalytic isomerization of straight chain paraffinic C4 through C6 hydrocarbons. It consists predominantly of saturated hydrocarbons such as isobutane, isopentane, 2,2-dimethylbutane, 2-methylpentane, and 3-methylpentane.' --> the test substance is slightly comparable to 'Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear'.

Result:The NOEC (72h) of the test substance 'Naphtha (petroleum), isomerization' to aquatic algae was calculated to be 0.1 mg/l and the EC50 (72h) was calculated to be 13 mg/l) [weight of evidence: ‘Toxicity to aquatic algae and cyanobacteria.002’].

 

Conclusion:The read across data suggest that the predicted aquatic toxicity of the substance 'Naphtha (Fischer-Tropsch), light, C4 -10 - branched and linear' by Peter Fisk Associates seems to be correct. It should be noted that the original study reports have not been reviewed.

 

Classification: The substance 'Naphtha (Fischer-Tropsch), light, C4 -10 - branched and linear' should be classified in the EU as R50- 53 ' Very toxic to aquatic organisms' and 'May cause long-term adverse effects in the aquatic environment'. The basis of this classification is the predicted EL50 of 0,55 mg/l to algae and the presence of components with log Kow >3. The biodegradability does not affect this.