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Long-term toxicity to aquatic invertebrates

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Description of key information

Based on the 21-reproduction study performed with Daphnia magna on Water Accommodated Fractions of hydrogenated terphenyl, a NOELR for reproduction < 1 mg/L, a NOELR for mortality = 1 mg/L and a NOELR for growth < 1 mg/L was determined. Two loading rates were tested (1 & 5 mg/L). At the Loading Rate of 1 mg/L, a 32% reduction of the reproduction was observed. As the test design did not include lower concentrations, this due to technical reasons (a.o. excessively large volumes of medium to be prepared beyond the lab space available for such medium preparation), no NOELR could be determined. Based on the ECHA Guidance on IR and CSA, Part R10, Table R10-1 the following approach is considered acceptable: “In case only a LOEC is given in the report, it can be used to derive a NOEC with the following procedures: LOEC > 10 and < 20% effect: NOE Two loading rates were tested (1 & 5 mg/L). At the Loading Rate of 1 mg/L, a 32% reduction of the reproduction was observed. As the test design did not include lower concentrations, this due to technical reasons, no NOELR could be determined. Based on the ECHA Guidance on IR and CSA, Part R10, Table R10-1 the following approach is considered acceptable: “In case only a LOEC is given in the report, it can be used to derive a NOEC with the following procedures: LOEC > 10 and < 20% effect: NOEC can be calculated as LOEC/2. If the effect percentage of the LOEC is unknown no NOEC can be derived.” In the case of this study, 1 mg/L can be regarded as the LOELR for this study. This LOELR would then be associated with a reproductive effect of 32%. This is higher than the boundaries provided by the R10 guidance, where a factor of 2 is considered applicable. However, in this case (with a 32% effect), an assessment factor of 10 is considered suitable as this greatly exceeds the assessment factor of 2. Based on the above mentioned reasoning, for risk assessment purposes it is assumed that the NOELR is > 0.1 but < 1 mg/L.

Key value for chemical safety assessment

Additional information

There is one 21 -day Daphnia magna reproduction study with hydrogenated terphenyl available (Tobor-Kaplon, 2014). The study was performed according to the OECD211 and GLP guidelines. The test was performed on Water Accommodated Fractions (WAFs) prepared at loading rates of 1.0 and 5.0 mg/L in triplicates. A 4-day period of magnetic stirring was applied in order to ensure maximum dissolution in test medium. The obtained mixtures were allowed to settle overnight. Subsequently, the aqueous WAFs were siphoned off, pooled and used as test solutions.

The reproduction test was performed in a semi-static system, included 10 vessels per test concentration and 20 vessels for an untreated control group. Each of the vessels contained one neonate (<24h old) Daphnia magna in 50 mL test medium. WAFs prepared at loading rates of 1.0 and 5.0 mg/L were tested in order to determine the NOELR for reproduction, mortality and growth. During the study samples for analyses were taken at 3 occassions. Samples were taken at the beginning and the end of one interval of 72 hours and two intervals of 48 hours. Concentrations of o-Terphenyl and m-Phenyl cyclohexyl benzene were analysed as they were identified as two main/relevant components. The analysis was performed to confirm repeatability of the preparation procedure and differences between applied treatments. Therefore, the effect parameters were expressed in terms of loading rates instead of measured concentrations. The study met the acceptability criteria prescribed by the protocol and was considered valid.

No mortality was observed in the control during the entire exposure period. In the lower loading rate one daphnid was found dead at day 18 of exposure. In the highest loading rate mortality reached 90% at day 3 of exposure. One daphnia survived in this treatment until the end of exposure. On average, 117 living young were produced per daphnid in the control treatment, while 80 and 8 living young were produced in WAFs prepared at 1.0 and 5.0 mg/L, i. e. resulting in 32 and 93% reduction of reproduction, respectively. The reproduction was significantly lower than in the control in both treatments. It should be noted that reproduction was calculated based on the number of introduced instead of surviving daphnids. This was done because the observed mortality was considered test substance related. The time to first brood was not affected by the test substance. The growth of daphnids was significantly reduced in both loading rates.

Effect parameters based on loading rates are summarized in below (in function of loading rate (mg/L):

·      NOELR for reproduction < 1.0 mg/L

·      NOELR for mortality = 1.0 mg/L

·      NOELR for growth < 1.0 mg/L