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Long-term toxicity to aquatic invertebrates

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Description of key information

The lowest valid NOEC for chronic toxicity to freshwater invertebrates is 1.74 mg Sb/L for Daphnia magna (Heijerick and Vangheluwe, 2003).

There are no valid chronic studies with marine invertebrates.

Key value for chemical safety assessment

Additional information

There is one study available providing reliable long term data for aquatic invertebrates (Heijerick and Vangheluwe, 2003).

Heijerick and Vangheluwe (2003) performed a 21-d chronic toxicity test with Daphnia magna using SbCl3as the test substance. This study, which is in accordance with the OECD 211 guideline, was conducted as a semi-static test, with full renewal of the test medium three times/week. The test was performed with five measured concentrations (range: 0.056 – 9.96 mg Sb/L) and a control, with ten test chambers per concentration, using one juvenile (<24h-old) daphnid in each chamber. Mortality of adult organisms was noted and newborn neonates were counted and removed when the exposure medium was renewed. Two endpoints, based on survival and reproduction (net reproduction rate, R, and the intrinsic rate of natural increase, rm) were determined. The resulting 21-d NOEC for reproduction of Daphnia magna was 1.74 mg Sb/L, with a LOEC of 3.13 mg Sb/L. The LC50 (21-d) was 4.77 mg/L, the EC50, R (21-d) was 3.82 mg/L, and the EC50, rm (21-d) was 4.86 mg/L.

The study by Kimball (1978) only contains reliable results for a 7-d screening test on Daphnia magna. The 7-d screening test was conducted as a static renewal test with exposure to trivalent antimony (SbCl3). The test was performed with four replicates, six concentrations (range: 1.9 – 52.2 mg Sb/L) and a control, with ten test chambers per replicate, using one 2-week old adult daphnid in each chamber. Once the daphnids began reproducing, the neonates and the moults of the adults were counted. Survival was recorded at each renewal period (three times weekly). The resulting 7-d NOEC for reproduction of Daphnia magna was 3.9 mg Sb/L. The LC50 for the 7-d screening study was 14.5 mg/L. The set-up for the 28-d test was identical to the screening test, except that neonate daphnids , instead of two week old adults, were placed into the beakers and the concentration range used was 0.52- 7.05 mg Sb/L. However, the results from the 28-d exposure period could not be used due to the high control mortality (30%).

The reasons why the study by Doe et al.(1987) on chronic toxicity of Daphnia magna is considered unreliable, even though the exposure concentrations were measured, are that there is no information presented on (i) the size of the groups (the only information given is that there was 1 animal/50 ml), (ii) the number and concentrations that were used, (iii) dose-response curves (no raw data are available), (iv) the number of replicates (if any), and (v) what statistics have been used to calculate the LC50 value and NOECs. The 30 day LC50 is 2.7 mg Sb/L and NOECs for reproduction (30d) and growth (33d) are 1.7 mg Sb/L and 0.8 mg Sb/L, respectively. However, the only information on concentrations is a legend in a figure indicating that one control and two doses of 1.7 mg Sb/L and 3.7 mg Sb/L have been used.

No information is available on the speciation of antimony in ecotoxicity tests, and the PNEC for antimony is therefore expressed in terms of the dissolved antimony concentration.