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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Experimental and calculated values are used to indicate the range of toxicity expected. Data on the toxicity of alkenes to algae 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 algae is not expected at C12 and above.

Key value for chemical safety assessment

Additional information

Pearson (1985) tested the acute toxicity of hex-1-ene to Pseudokirchneriella subcapitata. The study did not include analytical monitoring of the exposure concentrations, and the authors note that the test substance was not wholly soluble at the higher test concentrations. For this reason, the results from this study have been interpreted based on the highest nominal concentration below the limit of solubility, a test concentration of 22mg/l. At this concentration no effects were observed. Due to the lack of analytical monitoring, this study is not used as a key study.

Hoberg (2003c) tested the acute toxicity of hexene to Pseudokirchneriella subcapitata in an OECD Guideline 201 test, which included analytical monitoring of the test concentrations. Results are reported based on the geometric mean measured exposure concentrations. The 96 hour EC50 of >5.5 mg/L for growth rate is supported by a QSAR 96 hour EC50 of 3.2 mg/L for hex-1-ene (Nabholz and Mayo-Bean, 2009) and a EL50 of 8.4mg/l for hexene (DiToro et al, 2010).

No experimental data are available for C8 category members. Supporting QSAR values of EC50 of 1.1 mg/l for oct-1-ene (Nabholz and Mayo-Bean, 2009) and 1.5 mg/l for octene (DiToro et al, 2010) were calculated.

The toxicity of dec-1 -ene to Pseudokirchneriella subcapitata was investigated in an OECD 201 test (Brixham Environmental Laboratories, 2010e). 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 in sealed test vessels 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 three highest exposure concentrations had detectable levels of dec-1 -ene after 72 hours. Due to the loss of test compound over time the results are reported based on nominal loading rates. The 72 hour ErL50 lies between 1 and 1.8mg/l and the analytical monitoring indicates that the mean exposure concentration at 1.8mg/l was below the limit of solubility of dec-1 -ene. Supporting QSAR values of EC50 of 0.3 mg/l for dec-1-ene (Nabholz and Mayo-Bean, 2009) and 0.3 mg/l for decene (DiToro et al, 2010) were calculated.

The toxicity of dodec-1 -ene toPseudokirchneriella subcapitatawas investigated in an OECD 201 test (Harlan Laboratories, 2013). Due to the low solubility of the test substance the study was conducted as a limit test. A gas saturated solution was prepared by passing a steady stream of compressed air (0.5 L/minute) through a reservoir of test item and into a reservoir of test media for 48 hours to give a 100 % v/v saturated solution of the test item. The test was carried out in completely filled, sealed test vessels. Measured concentrations ranged from 0.0133 mg/L in the freshly prepared solutions to less than the limit of quantification (0.00013 mg/L) at 72 hours. After 72 hours there were no statistically significant differences from the control. These results are interpreted as demonstrating that the 72 hour EC50 of dodec-1 -ene is greater than 0.00093 mg/L and the corresponding NOEC is greater than or equal to 0.00093 mg/L, the limit of solubility in the test media.

The toxicity of dodec-1 -ene to Pseudokirchneriella subcapitata was also investigated in an OECD 201 test (Brixham Environmental Laboratories, 2010f). Due to the low solubility of the test substance the study used a solvent carrier, so this study is used as supporting data only. The test substance was mixed with the solvent beforebeing 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 in sealed test vessels to minimise the loss of the test substance. At the lower loading rates (0.032 -0.25mg/l) the measured concentrations were below the limit of detection (0.01mg/l) throughout the test. No effects were seen at these loading rates. A 77% effect was observed at 0.5mg/l, the next highest loading rate and a similar level of effect was also observed at the 1 and 2mg/l loading rates. Exposure concentrations at the 0.5mg/l loading rate were at the limit of detection at the start of the exposure and had dropped below the limit of detection after 72 hours. An ErL50 has therefore not been calculated. Instead the results based on loading rate are a 72 ErL50 of 0.25 -0.5mg/l and are interpreted as indicating effects below the limit of solubility. Supporting QSAR values of EC50 of 0.09 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.

Thompson and Swigert (1995) tested the toxicity of tetradec-1 -ene to Selenstrum capricornutum in an OECD 201 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. The 96 hour EL50 was >1000mg/l WAF, a NOELR was not reported.

Hudson (1999) tested the toxicity of tetradec-1 -ene and tetradecene to Skeletonema costatum in an ISO 10523 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 with four exposure concentrations up to a maximum loading rate of 1000mg/l WAF. The 48 hour EL50 was >1000mg/l WAF, a NOELR was not reported. Supporting QSAR values of no toxicity expected at the limit of solubility for tetradec-1-ene (Nabholz and Mayo-Bean, 2009) and tetradecene (DiToro et al, 2010) were calculated.

Douglas and Halls (1993) tested the toxicity of hexadec-1 -ene to Selenastrum capricornutum in an OECD 201 test. Due to the low solubility of the test substance test organisms were exposed to water accommodated fractions (WAF) and exposure concentrations expressed were as a loading rate. The test was conducted as a limit test with a single exposure concentration of 1000mg/l WAF. The 72 hour EL50 was >1000mg/l WAF and the 72 hour NOELR was 1000 mg/l WAF.

Hudson (1999) tested the toxicity of hexadec-1-ene to Skeletonema costatum in an ISO 10523 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 with four exposure concentrations up to a maximum loading rate of 1000 mg/l WAF. The 48 hour EL50 was >1000 mg/l WAF, a NOELR was not reported.

Whale (1995) tested the toxicity of alkenes, C15 - 18 to Skeletonema costatum in a study following PARCOM guidelines. 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. No effects were observed at the highest loading rate. The 72 hour EL50 is >1000 mg/l WAF and the 72 hour NOELR is 1000 mg/l WAF.

Roddie (1995) tested the toxicity of alkenes, C16 - 18 to Skeletonema costatum in an ISO 10523 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. No effects were observed at the highest loading rate. The 72 hour EL50 is >5600 mg/l WAF and the 72 hour NOELR is 5600 mg/l WAF.

Roddie (1998) tested the toxicity of alkenes, C16 - 18 to Skeletonema costatum in an ISO 10523 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 72 hour EL50 is 4777 mg/l WAF.

Douglas (1993) tested the toxicity of C20 -24 alpha olefins to algae in an OECD 201 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 study was conducted as a limit test with a single loading rate of 1000mg/l WAF. The 72 hour EL50 was >1000mg/l WAF.

Pateman (1998) tested the toxicity of alkenes, C20 -24 to Pseudokirchnerella subcapita in an OECD 201 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 effects were observed at this loading rate, so the 72 hour EL50 >1000mg/l WAF and the NOELR is 1000mg/l WAF.

Vryenhoef and Mullee (2008) tested the toxicity of alkenes, C20 - 24 to Desmodesmus subspicatus in an OECD 201 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 effects were observed at this loading rate, so the 72 hour EL50 is >100 mg/l WAF and the NOELR is 100 mg/l WAF.

The experimental data indicates that toxicity to algae increases with carbon number from C6-C10, as log Kow increases. At carbon numbers above this acute toxicity is not observed at the limits of solubility. The QSAR values are in good agreement with the experimental data, although ECOSAR predicts that toxicity would be observed at C12. As experimental data is available at C6, C10, C12 and C14 this is used as key, with values for C8 filled by read across from the available experimental data and QSAR values.

 

The available data for C6-C14 is summarised in the table below:

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

·        C8 – toxicity is set at 1 – 10 mg/l based on weight of evidence

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

·        C12 and higher – no toxicity to algae and aquatic plants is expected (Harlan, 2013; Hudson, 1999; Thompson and Swigert, 1995)

Major Carbon Number

6

8

10

12

14

Experimental

Hexene EC50 >5.5mg/l M

nd

Dec-1-ene EL50 1-1.8 mg/l N

Dodec-1-ene > sol 

Tetradec-1-ene > sol Tetradecene > sol

ECOSAR

EC50 3.2mg/l

EC50 1.1mg/l

EC50 0.3mg/l

EC50 0.09mg/l

EC50 >sol

PETROTOX

EL50 8.4mg/l

EL50 1.5mg/l

EL50 0.3mg/l

EL50 >sol

EL50 >sol

M = measured. N = nominal.

At C14 and above the log Kow of the substance is above 6.4, the maximum log Kow within ECOSAR. These values should therefore be viewed as indicative.