Alkenes, C8-10-branched, C9-rich

Short-term toxicity to aquatic invertebrates

Description of key information

Data on the toxicity of alkenes to aquatic invertebrates is available for the carbon number range C6 –C24. Two QSAR have also been run to support the experimental data (Nabholz and Mayo-Bean, 2009; DiToro et al, 2010). Acute toxicity to invertebrates is not expected at C12 and above.

Additional information

Hoberg (2003) tested the acute toxicity of hexene to Daphnia magna in an OECD Guideline 202 test, which included analytical monitoring of the test concentrations. Results are reported based on the geometric mean measured exposure concentrations. The 48 hour EC50 of 4.4 mg/L is supported by a QSAR 48 hour EC50 of 4.2 mg/l for hex-1-ene (Nabholz and Mayo-Bean, 2009) and 20 mg/l for hexene (DiToro et al, 2010).

No experimental data are available for C8 category members. Supporting QSAR values of EC50 of 0.9 mg/l for oct-1-ene (Nabholz and Mayo-Bean, 2009) and 3.6 mg/l for octene (DiToro et al, 2010) were calculated.

The toxicity of dec-1 -ene to Daphnia magna was investigated in an OECD 202 test (Brixham Environmental Laboratories, 2010). Due to the low solubility of the test substance the study used a solvent carrier. The test substance was mixed with the solvent before being added to the dilution water. It was then stirred for 48 hours under sealed conditions to maximise the exposure concentrations. The test was carried out with sealed test vessels and the solutions were renewed daily to minimise the loss of the test substance. At the lower loading rates (0.056 -0.1mg/l) the measured concentrations were below the limit of detection throughout the test. Only the highest exposure concentration had detectable levels of dec-1 -ene after each 24 hour renewal period. Due to the loss of test compound over time the results are reported based on nominal loading rates. The 48 hour EC50 lies between 0.56 and 1 mg/l and the analytical monitoring indicates that the mean exposure concentration at 1mg/l was below the limit of solubility of dec-1 -ene. Supporting QSAR values of EC50 of 0.2 mg/l for dec-1-ene (Nabholz and Mayo-Bean, 2009) and 0.7 mg/l for decene (DiToro et al, 2010) were calculated.

The toxicity of dodec-1 -ene to Daphnia magna was investigated in an OECD 202 test (Harlan Laboratories, 2013). Due to the low solubility of the test substance, the study used a saturated solution. The organisms were exposed to a 100 % gas saturated solution of dodec-1 -ene prepared by passing a steady stream of compressed air through a reservoir of test item and into a reservoir of test media for 24 hours. The test was carried out with sealed test vessels and the solutions were renewed daily to minimise the loss of the test substance. Measured concentrations ranged from 0.00846 mg/L to 0.00973 mg/L in the freshly prepared solutions. The concentration in the old test media declined to 0.00123 mg/L in the 24 hour sample and less than the limit of quantification (0.00010 mg/L) in the 48 hour sample. After 48 hours there were no mortalities in the control or single exposure concentration. These results are interpreted as demonstrating that the 48 hour EC50 of dodec-1 -ene is greater than 0.0028 mg/L, the limit of solubility in the test media.

The toxicity of dodec-1 -ene to Daphnia magna was also investigated in an OECD 202 test (Brixham Environmental Laboratories, 2010). Due to the low solubility of the test substance the study used a solvent carrier, so this is used as supporting data only. The test substance was mixed with the solvent before being added to the dilution water. It was then stirred for 48 hours under sealed conditions to maximise the exposure concentrations. The test was carried out with sealed test vessels and the solutions were renewed daily to minimise the loss of the test substance. At the lower loading rates (0.032 - 0.18 mg/l) the measured concentrations were below the limit of detection (0.01 mg/l) throughout the test. No effects were seen at these loading rates. A 55% effect was observed at 0.32 mg/l, the next highest loading rate. Exposure concentrations at this loading rate were detectable throughout the exposure period except during the final 24 hour period when concentrations fell from 0.058 to <0.01 mg/l following the final exchange. The EC50 therefore lies between loading rates of 0.18 and 0.32mg/l and the analytical monitoring indicates that the mean exposure concentration at these loading rates was <0.063mg/l. Supporting QSAR values of EC50 of 0.033 mg/l for dodec-1-ene (Nabholz and Mayo-Bean, 2009) and no toxicity expected at the limit of solubility for dodecene (DiToro et al, 2010) were calculated.

Drottar and Swigert (1995) tested the toxicity of tetradec-1 -ene to Daphnia magna in an OECD 202 test. Due to the low solubility of the test substance test organisms were exposed to water accommodated fractions (WAF) and exposure concentrations expressed as a loading rate. The test was conducted as a limit test with a single exposure concentration of 1000mg/l WAF. No immobilisation was observed at this loading rate, so the 48 hour EL50 >1000mg/l WAF.

Whale and Cheesman (1995) tested the toxicity of tetradec-1 -ene to the marine species Acartia tonsa in an OECD 202 test. Due to the low solubility of the test substance test organisms were exposed to water accommodated fractions (WAF) and exposure concentrations expressed as a loading rate. The test was conducted as a limit test with a single exposure concentration of 1000mg/l WAF. 78% immobilisation was observed at this loading rate.

Both studies follow the same method and prepare the WAF in a similar and appropriate manner. However, the results of the two studies vary greatly. The major difference between the studies is that Drottar and Swigert use the standard freshwater test organism Daphnia magna, while Whale and Cheesman use Acartia tonsa, a non-standard marine species. Due to this the study with Daphnia has been selected as the key study. Supporting QSAR values of 0.006 mg/l for tetradec-1-ene (Nabholz and Mayo-Bean, 2009) and no toxicity expected at the limit of solubility for tetradecene (DiToro et al, 2010) were calculated.

Christensen (1996) tested the toxicity of tetradecene to Mysidopsis bahia in a guideline study. Due to the low solubility of the test substance used a Suspended Particulate Phase (SPP) approach was used. A single SPP solution formed from 500ml test substance in 4500ml dilution water was diluted to form the various test concentrations. Increased mortality was not seen at the highest tested concentration of 1000000mg/l SPP.

Christensen (1996) tested the toxicity of alkenes, C15 - 18 to Mysidopsis bahia. Due to the low solubility of the test substance test organisms were exposed to water accommodated fractions (WAF) and exposure concentrations were expressed as a loading rate. The study was conducted as a limit test. The 96 hour EL50 was >1000 mg/l WAF.

Whale (1995) tested the toxicity of alkenes, C15 - 18 to the marine species Acartia tonsa. Due to the low solubility of the test substance test organisms were exposed to water accommodated fractions (WAF) and exposure concentrations expressed as a loading rate. The 48 hour EL50 was > 1000 mg/l WAF.

Douglas and Halls (1993) tested the toxicity of hexadec-1-ene to Daphnia magna in an OECD 202 test. Due to the low solubility of the test substance test organisms were exposed to water accommodated fractions (WAF) and exposure concentrations were expressed as a loading rate. A single stock solution of 1000mg/l WAF was prepared and then diluted to achieve the lower test concentrations. WAF should be prepared by adding the appropriate amount of test substance to the test media, rather than by dilution. Therefore, only the results from the 1000 mg/l WAF are considered valid. 85% immobilisation was observed at this loading rate.

Whale and Cheesman (1995) tested the toxicity of hexadec-1-ene to the marine species Acartia tonsa in an OECD 202 test. Due to the low solubility of the test substance test organisms were exposed to water accommodated fractions (WAF) and exposure concentrations were expressed as a loading rate. The test was conducted as a limit test with a single exposure concentration of 1000 mg/l WAF. 81% immobilisation was observed at this loading rate.

Douglas and Halls (1993) tested the toxicity of C20 -24 alpha olefins to Daphnia magna in an OECD 202 test. Due to the low solubility of the test substances test organisms were exposed to water accommodated fractions (WAF) and exposure concentrations expressed as a loading rate. The exposure concentrations were prepared by the dilution of a 1000mg/l WAF, rather than by adding the appropriate amount of test substance to water and generating separate WAFs. We have therefore only reported results from the single loading rate of 1000mg/l. 100% effect levels were observed after 48 hours.

Wetton (1998) tested the toxicity of alkenes, C20 -24 to Daphnia magna in an OECD 202 test. Due to the low solubility of the test substance test organisms were exposed to water accommodated fractions (WAF) and exposure concentrations expressed as a loading rate. The studies were conducted as limit tests. The 48 hour EL50 was >1000mg/l WAF.

Vryenhoef and Mullee (2008) also tested the toxicity of alkenes, C20 - 24 to Daphnia magna in an OECD 202 test. Due to the low solubility of the test substance test organisms were exposed to water accommodated fractions (WAF) and exposure concentrations were expressed as a loading rate. The test was conducted as a limit test with a single exposure concentration of 100 mg/l WAF. No immobilisation was observed at this loading rate, so the 48 hour EL50 is >100mg/l WAF.

The experimental data indicates that toxicity to aquatic invertebrates increases with carbon number from C6-C10, as log Kow increases. At carbon numbers above this the majority of studies indicate that acute toxicity is not observed at the limits of solubility, and this is supported by the known mode of action of these chemicals as non-polar narcotics. Four of the older studies report acute effects in studies with C14, C16 and C20-24 alpha olefins. However, additional studies for the same or similar compounds report no acute effects. The QSAR values are in good agreement with the experimental data, although Nabholz and Mayo-Bean (2009) and DiToro et al (2010) disagree as to where toxicity is no longer observed. As experimental data is available at C6, C10 and C12 and C14 this is used as key, with values for C8 filled by read across from the available experimental data and QSAR values.

Summary

·        C6 – toxicity is observed at 1 – 10 mg/l (Hoberg 2003a)

·        C8 – toxicity is set at ~ 1mg/l based on weight of evidence

Note whether this is just above or below 1 is irrelevant for classification as data is available for fish indicating toxicity <1 mg/l.

·        C10– toxicity is set at <1 mg/l (Brixham Environmental Laboratories 2010c)

·        C12 and higher – no toxicity to invertebrates is expected (Harlan, 2013; Christensen, 1996; Drottar and Swigert, 1995)

Major Carbon Number	6	8	10	12	14
Experimental	Hexene EC50 4.4mg/l M	nd	Dec-1-ene EC50 0.56-1 mg/l N	Dodec-1-ene >sol	Tetradec-1-ene > sol Tetradecene > sol
ECOSAR	EC50 4.2mg/l	EC50 0.9mg/l	EC50 0.2mg/l	EC50 0.033mg/l	EC50 0.006mg/l
PETROTOX	EL50 20mg/l	EL50 3.6mg/l	EL50 0.7mg/l	EL50 >sol	EL50 >sol

M = measured. N = nominal.

At C8 and above the log Kow of the substance is above 5, the maximum