Benzene, C15-16-alkyl derivs.

Endpoint summary

Additional information

In cases where no data were available on the target substance, Benzene, C15-16-alkyl derivs., data were read across from a structurally related material (the test substance).

FISH

Short-term toxicity to fish

The key study (ANON, Instituto di Ricerche Biomediche 1999) determined the toxicity of a read-across source substance for Benzene, C15 -16 -alkyl derivs. to fish in an extended acute study. Fish were exposed for 14 days to a water accommodated fraction of 0, 5, 6.5, and 10 µg/L of test substance. The test medium was renewed daily. Fish were monitored daily for toxicity during the study for swimming behaviour, reaction to stimuli, discoloration, food intake, and mortality. All fish were weighed and measured before the test and survivors were weighed at test termination. No adverse effects were observed for the concentrations tested during the study period. A decrease in the test substance concentration was observed within 24 hours (day 1 and day 14), but the daily renewal of test solutions maintained the exposure to the test substance. Both the LOEC and NOEC were higher than the solubility concentration of >10 µg/L/day.

Long-term toxicity to fish

An OECD 203 study (Fernandez, et al. 2000a) with zebra fish (Danio rerio) was conducted in which the exposure period was extended to 21 days. Fish were exposed to a read-across source substance for Benzene, C15 -16 -alkyl derivs. in a flow-through system at a limit concentration of 58 µg/L using acetone as a solvent. Fish were fed with Nutrafin once every three days during the test. No mortality was observed in the treatment solutions during the study. No toxic symptoms were observed. The 21-day NOEC is therefore greater than the limit dose of 58 µg/L. The lack of fish toxicity is consistent with expectations. Overall, a read-across source substance for Benzene, C15 -16 -alkyl derivs. has very low water solubility and in a 14-day study with fish there were no effects at the limits of water solubility. In fact, in short-term tests conducted by Gledhill et al. (1991), fish were unaffected even at nominal concentrations of 1000 mg/L and with the test substance visibly floating on the surface of the test vessels. Furthermore, short-term studies conducted with aquatic invertebrates and algae indicated no dose-responsive effects at the water solubility limit. Finally, a 21-day long-term study in Daphnia was conducted and resulted in a LOAEC of 0.015 mg/L (15 µg/L). Based on the generally greater sensitivity of Daphnia than fish, the lack of bioaccumulation potential, the available fish, invertebrate and algae data, and in accordance with Annex IX, Section 9, column 2 of the REACH regulation, a long-term toxicity study in fish is not deemed necessary.

AQUATIC INVERTEBRATES

Short-term toxicity to aquatic invertebrates

The key study (Verge, et al. 1999) determined the short-term toxicity of a read-across source substance for Benzene, C15 -16 -alkyl derivs. to Daphnia magna. A test solution was prepared, without use of solvent, to reach the solubility concentration (0.041 mg/L). Daphnids were then exposed to concentrations of 0, 12.5%, 25%, 50%, 75%, and 100% of the saturated test solution for 48 hours. At the end of this period, the daphnids were observed for mobility. Though immobilized daphnids were seen at four test concentrations, there was no dose-responsive increase in immobilization, nor was the number of immobilized daphnids significantly increased over the negative controls. Therefore, the 48-hr EC50 is >0.041 mg/L (>41 µg/L), which is greater than the limits of water solubility for the test substance.

A second study (Fernandez, et al. 2000b) also used the OECD 202 guidelines but extended the exposure period up to 96 hours and beyond (up to 144 hours). Acetone was used to enhance water solubility. The study focused on a series of seven LAB homologues with alkyl chains ranging from C4 up to C18. Results indicate 48 hr EC50 values > 0.1 mg/L (>100 µg/L) for all LAB homologues tested. Exposure time periods greater than 96 hours resulted in values below the water solubility limit (Fernandez et al. 2000b). The EC50 values for homologues C10 and C12 are particularly relevant because the average alkyl chain length for commercial LAB is C11.6. EC50 results at 96 hours were 82.9 and 61.9 µg/L for the C10 and C12 homologues, respectively, both above the measured water solubility limit. EC50 values at 120 hours were 35.3 and 27.8 µg/L for C10 and C12, respectively. EC50 values at 144 hours (6 days) were 24.8 and 27.8 µg/L for C10 and C12, respectively, which are slightly below the solubility measured in the water solubility test.

Long-term toxicity to aquatic invertebrates

The key study (Gledhill, et al. 1991) examined the effects of chronic exposure of Daphnia magna to the test substance. Groups of 10 daphnids were exposed to the test substance for 21 days using a flow-through procedure and a solvent (acetone). Ten first-instar Daphnia (<24 h old) were placed in each of four replicate chambers for each test substance concentration, the control and the solvent control. Reproduction was assessed three times weekly. Biological parameters (adult survival, young produced, young produced per adult) were assessed on days 0, 4, 7, 14, and 21. The 21-day NOAEC for daphnids was 0.0075 mg/L (7.5 µg/L) and the LOAEC was 0.015 mg/L (15 µg/L) test substance. The results can be considered conservative as the potential for sediment partitioning and biodegradation as would occur in nature was minimized in the laboratory systems. Growth was established only at day 21.

The second key study (Minderhout, et al. 2013) was intended to determine the effects of a read-across source substance for Benzene, C15-16-alkyl derivs. on the survival, growth and reproduction of Daphnia magna, during a 21-day exposure period under semi-static test conditions. The test organisms were exposed to the test substance at nominal Water Accommodated Fraction (WAF) loading rates of 0.01 to 10 mg/L under semi-static conditions for 21 days. There were no statistically significant treatment-related effects on survival, reproduction or growth at concentrations ≤10 mg/L, the highest nominal WAF loading rate tested. Consequently, the NOELR was 10 mg/L. The LOELR was >10 mg/L and the Maximum Acceptable Toxicant Level (MATL) was calculated to be >10 mg/L. The 21-day EL50 value for adult immobility and reproduction were both >10 mg/L, the highest nominal WAF loading rate tested.

ALGAE AND AQUATIC PLANTS

Effects on algae and aquatic plants

The key study (PETRESA 2000) examined the toxicity of various LABs to aquatic algae. Tests were also done on C10, C12, and C14 linear alkyl benzenes in addition to the commercial LAB. Scenedesmus subspicatus was exposed to the test substances for 72 hours. During this time, readings of the growth rate were taken. The nominal concentrations tested were 25, 50 and 100 µg/L, with corresponding measured concentrations of 23, 25, and 98 µg/L, respectively, for the C12-LAB. The 72-hr EC50 values for all substances were >100 µg/L (nominal), which is higher than the measured solubility limit for C12-LAB (37.6 µg/L).