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Toxicity to aquatic plants other than algae

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Description of key information

The only valid value for acute toxicity to freshwater plants is a 4-day EC50 >25.5 mg Sb/L for Lemna minor (Brooke et al, 1986).

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Brooke et al. (1986) exposed Lemna minor for 4 days to trivalent antimony (SbCl3) in a static test design. The endpoint studied was reduction in frond production. The test was performed in quadruplicate with five concentrations (range: 1.6 - 25.5 mg Sb/L) and a control, with 20 fronds in each test chamber. No EC50 could be obtained. However, in the highest exposure group, i. e. 25.5 mg Sb/L, a significant reduction in frond production occurred (32 %). The resulting NOEC from this study was 12.5 mg Sb/L, with the corresponding LOEC of 25.5 mg Sb/L.

Fjallborg and Dave (2004) spiked sewage sludge with SbCl5 and after and equilibration period of 60 days, radish, oats or lettuce were grown. After 14 days cultivation the toxicity of the elutriate to Lemna minor was tested. The authors report that the dry weight of Lemna minor was not consistently affected by Sb concentration up to a maximum test concentration of 0.22 mg Sb/L. Although this study included analytical monitoring of the elutriate, its non-standard design and unbounded LOEC make it unsuitable for use in the assessment.

Duester et al (2011) evaluated the effect of antimony potassium tartrate (SbIII) and potassium hexahydroxoantimonate (SbV) on the growth of duckweed (L.minor) and the floating plant Wolffia arrhiza. As indicated in the discussion on their results for the green alga P.subcapitata, the results for antimony potassium tartrate are not reliable for antimony and antimony compounds. The 7d-EC50 for pentavalent antimony is >219 mg Sb/L for both floating plants, and are considered reliable. This unbounded value, however, is almost one order of magnitude higher than the unbounded value of >25.5 mg Sb/L that is reported by Brooke et al (1986).