Pentadecan-15-olide

Endpoint summary

Additional information

To assess the aquatic toxicity of the substance, studies are available on the registered substance and on a read-across substance (EC Number: 422-320-3). This supporting substance is considered adequate for read-across purpose (see Iuclid section 13 for justification).

Three weight of evidence studies are available to assess the short-term toxicity of the substance to fish. The first weight of evidence study (Caspers, 1994) was performed according to EU Method C.1 with GLP statement on the registered substance but was not deemed as reliable as aeration was used and substance loss may have occurred due to this. The two other weight of evidence studies (Stäbler, 2005 and Sewell, 1995) were performed according to OECD Guideline 203 and EU Method C.1 with GLP statement on the read-across substance and were considered reliable with restrictions. No effects were observed on fish over a 96 hours study period at any concentration up to the solubility limit of the test substance. Therefore, no acute LC50 value can be calculated for fish.

Five studies are available to assess the acute aquatic toxicity to invertebrates, of which two were performed on the registered substance (Harris, 2013; Caspers, 1995) and three were performed on the read-across substance (Harris, 2013; Stäbler, 2005a; Stäbler, 2005b). In these 48 h daphnid acute studies, no effects were found up to and including the maximum solubility of the test substance in aqueous test medium, except the study from Stäbler (2005b) where effects were observed but well above maximum water solubility and quite obviously due to physical adhesion to an oily film at the test vessel surface. No EC50 can therefore be calculated for acute effects on invertebrates.

Four studies are available to assess the toxicity of the substance to aquatic algae. The first study (Caspers, 1996), assessed as the key study, was performed according to EU Method C.3 with GLP statement on the registered substance. Under the conditions of this test, no ErC50 value can be derived for algae either as insufficient toxicity was observed (72h-ErC50 > 0.47 mg/L, the highest tested concentration) but some effects were observed indicating a potential for mild toxicity close to the solubility limit in the early stages of the study, although the 72h-ErC10 value based on growth rate was greater than the solubiltiy limit at 0.42 mg/L. The other studies (Scheerbaum, 2005; Dengler, 2005; Sewell, 1995), assessed as supporting studies, were performed according to OECD Guideline 201 and EU Method C.3 with GLP statement on the read-across substance. No ErC50 value can be derived for algae because either insufficient toxicity was observed or effects were observed at concentrations greater than the solubility limit. However, some mild effects were observed, especially in the first day of the study although this diminished over the study period, indicating a mild potential for toxicity close to the solubility limit (worst case 72h-ErC10 value at 0.73 mg/L), but it is not clear if these effects are physical or due to actual toxicity of the substance. It is not possible to maintain this concentration under the conditions of an algae study due to degradation and adsorption of the substance during the test. In conclusion, according to the key study performed on the registered substance, no ErC50 can be derived for algae but the 72h-ErC10 at 0.42 mg/L is used as the key value, greater than the solubility limit of the registered substance.

One key study is available to assess the long-term toxicity to fish. This study (Sewell, 2003) was performed according to international guidelines with GLP statement on the read-across substance to assess the effects of the test material on freshly laid eggs of the fathead minnow (Pimephales promelas). Despite significant limitations concerning out of bounds and systematic differences between groups for temperature, unexplained mortality in a single replicate and statistical differnces between the control and solvent control, the study is nevertheless considered valid but an extreme worst case endpoint value. The NOEC value, based on the mean measured test concentrations of the centrifuged test media, was considered to be 0.027 mg/L, in terms of length and weight.

Two studies are available to assess the long-term toxicity of the substance to aquatic invertebrates. The first study (Caspers, 1996), assessed as the key study, was performed on the registered substance following a method similar to OECD Guideline 211 with GLP statement. The 21d-NOEC based on reproduction and the time-weighted mean of measured test concentrations of the test media was 0.068 mg/L. The second study (Sewell, 2002), assessed as the supporting study, was performed according to OECD Guideline 211 with GLP statement on the read-across substance. The 21d-NOEC based on the time-weighted mean of measured test concentrations of the test media was 0.039 mg/L. This result should be considered with care. Both effect patterns are similar between these two studies (100% mortality at the highest concentration in each test and no effects were observed at all other concentrations). This set of results is not ideal to derive a reliable NOEC as there is no dose response relationship, however, both the measured concentrations and effects observed of these studies seem very much consistent. The study from Caspers provides a better approximation of the NOEC value than the study from Sewell based on tested concentrations because the difference between the NOEC and the LOEC is significantly greater (a factor of 4.1) than for the study on the registered substance (a factor of 1.9). Therefore, the key value retained for the long-term toxicity to aquatic invertebrates is a NOEC value of 0.068 mg/L.

 

Two studies are available to assess the toxicity of the substance to microorganisms. The first activated sludge respiration inhibition test (Dengler, 2005), assessed as the key study, was performed according to OECD Guideline 209 and EU Method C.11 with GLP statement on the read-across substance. There was no inhibitory effect of the test item at any concentration. The EC50 and NOEC were above 100 mg/L. The second activated sludge respiration inhibition test (Caspers, 1996), assessed as the supporting study, was performed according to ISO Guideline 8192, similar to OECD Guideline 209 with GLP statement on the registered substance. No deviation from the negative control was observed, whatever the substance concentration, therefore the EC50 is considered to be greater than 10 000 mg/L. In conclusion, according to the key study, the key NOEC value used for chemical safety assessment is taken as 100 mg/L as a worst case value.

 

In conclusion, no effects were found in acute studies although they were observed in long term studies on daphnids and fish with fish being the most sensitive endpoint. The key NOEC value used for PNEC derivation is 0.027 mg/L, for fish.

 

The table below summarized the conclusion:

	Acute values L(E)C50, mg/L	Chronic values NOEC/EC10, mg/L
Fish	No acute 96h-LC50 value	33d-NOEC = 0.027 mg/L.
Aquatic invertebrates	No acute 48h-EC50 value	21d-NOEC = 0.068 mg/L.
Aquatic algae	No acute 72h-ErC50 value	72h-ErC10 = 0.42 mg/L
Microorganisms	3h-EC50 > 100 mg/L;	3h-NOEC ≥ 100 mg/L