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Ecotoxicological information

Toxicity to soil macroorganisms except arthropods

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Reference
Endpoint:
toxicity to soil macroorganisms except arthropods: long-term
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to Read-across statement attached in Section 13.
Reason / purpose for cross-reference:
read-across source
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
32 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
reproduction
Remarks:
and growth
Details on results:
At concentrations of 100 mg Cr/kg dry soil and higher, reproduction was significantly reduced, while growth was only significantly reduced at the highest concentration tested (1000 mg Cr/kg dry soil). It can be concluded that earthworm concentrations exceeding 3 mg Cr /kg dry weight are toxic for E. andrei. Chromium is rapidly eliminated from the worms, suggesting that no strong binding within the earthworms occurred.
Reported statistics and error estimates:
EC50 values for the effect of zinc on earthworm reproduction were calculated according to a logit model. NOECs were calculated using William's test or Dunnett's test in the TOXSTAT software package and Student's t test.
Validity criteria fulfilled:
yes
Conclusions:
Reliable study, NOEC used for PNEC derivation.
Executive summary:

Van Gestel et al. (1993) carried out an OECD 21-day earthworm reproduction test using Eisenia andrei in artificial soil at 2°C at different nominal test concentrations (0 -100 -180 -320 -560 -1000 mg/kg). 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.

Description of key information

Van Gestel et al. (1993) carried out an OECD 21-day earthworm reproduction test using Eisenia andreii n artificial soil at 2°C at different nominal test concentrations (0 -100 -180 -320 -560 -1000 mg/kg). 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.

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for soil macroorganisms:
32 mg/kg soil dw

Additional information

The study of Sivakumar (2005) was conducted to evaluate the effects of Cr(VI) on the survival, behavior, and morphology of the earthworm, Eisenia fetida, in water at pH 6, 7, and 8 and their toxicity in 10 different soils and an organic substrate. Six concentrations of 100, 150, 200, 250, 300, and 350 mg Cr/kg were applied to the test animals in the definitive test. The 14-day LC50 values of Cr(VI) in all soils ranged from 222 mg/kg to 257 mg/kg at pH 6, 7 and 8. The LC50 values of Cr(VI) was 219 mg/kg in the organic substrate. Changes were not observed in the morphology of earthworms and in their burrowing behavior in both soil and organic media at all test concentrations. The soil variables that showed significant correlations with LC50 values were considered in the development of regression equations. The equations showed that clay alone accounted for 92% of the variation in the toxicity (LC50 values) of Cr(VI).

Further, Cr(VI) availability in soils may also be reduced because of its reduction to Cr(III) in the presence of reducing agents and the higher affinity of the latter (30- to 300 - fold) to soil clay minerals than Cr(VI).

The toxicity of Cr(VI) was four and seven times greater than that of Cr(III) in water and soil, respectively. Stepwise multiple regression analysis predicted that the clay content of soils accounted for 92% and 88% of the variation in the LC50 values of Cr(III) and Cr(VI), respectively.

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