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A number of studies investigating terrestrial toxicity are available and are summarised in the RAR and are reproduced below. Further studies to address this endpoint may be required, based on the outcome of exposure modelling.

Extract from EU RAR (2005):

Once released into soil, it is likely that much of the chromium (VI) present will be reduced to chromium (III). Toxicity data are available for chromium (VI) in soil, but it is also likely that in these experiments the majority of the chromium present will be converted to chromium (III) during the test.

Van Gestel et al. (1993) carried out an OECD 21-day earthworm reproduction test using Eisenia andrei in artificial soil at 20oC. The source of chromium used in the experiment was chromium (III) nitrate. Reproduction was found to be significantly reduced at chromium concentrations of 100 mg Cr/kg dry soil and above, while growth was significantly reduced only at a concentration of 1,000 mg Cr/kg dry soil. The NOEC from the study was 32 mg/kg dry soil. At the end of the three week exposure period, the earthworms were placed in clean soil for a further 21 days. At the end of this period, the reproduction of the earthworms had virtually recovered to that of the control organisms.

Moulinier and Mazoyer (1968) reported the results of plant toxicity tests using two forms of chromium (III), chromic oxide and chromic sulphate. Two soils were used in the test, the first had a pH of 5.5 and the other had a pH of 8.3. Wheat (variety Florence-Aurore) and tomatoes (variety John Moran) were grown in the soil spiked with various concentrations of chromium (III) (10-500 mg Cr/kg soil for wheat; 20-1,000 mg Cr/kg soil for tomatoes). Chromium (III), in the form of chromic sulphate, was shown to reduce the yields of wheat at concentrations of 200 mg Cr/kg and greater in the acid soil, and around 100 mg Cr/kg soil and greater in the alkaline soil. No effects were seen with chromium (III) in the form of the insoluble oxide. The paper concluded that chromium (III) in the form of chromic sulphate may adversely affect the yields of wheat and tomatoes. The reduction in yield was concurrent with a lower phosphate concentration in the plants. The toxic effects seen were found to be suppressed by the addition of either calcium carbonate or monobasic calcium phosphate to the soil.

Crommentuijn et al. (1997) reviewed the toxicity of chromium (III) to soil processes. The results of 51 determinations were reported, covering arylsulphatase, nitrification, N-mineralisation, phosphatase, respiration and urease. The test results ranged from 1.0 mg/kg dw to 3,332 mg/kg dw (both values being for arylsulphatase). All studies used soluble chromium (III) compounds, largely chromic (III) chloride. For this risk assessment, data were selected from this survey, taking values where a NOEC was obtained directly or where the LOEC related to an effect level of 20% or less (and using LOEC/2 as the NOEC). A total of 37 values were obtained, and a further selection was made giving preference to longer exposure times in the same studies, resulting in a final data set of 30 values. The statistical extrapolation method has been used to derive an HC5-50% value of 5.9 mg/kg.