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Ecotoxicological information

Toxicity to soil microorganisms

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Reference
Endpoint:
toxicity to soil microorganisms
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
See Read-across statement in section 13 for justification.
Reason / purpose for cross-reference:
read-across source
Dose descriptor:
EC50
Remarks:
extrapolation, see below
Effect conc.:
5.9 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
not specified
Basis for effect:
other: see table below
Remarks on result:
other: see table below
Details on results:
The test results ranged from 1.0 mg/kg dw to 3,332 mg/kg dw (both values being for arylsulphatase).

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.

The values used in this risk assessment were selected from those presented in Table 4.4 of Appendix IV in the Crommentuijn review, applying the following criteria. Values for the NOEC or EC10 which were reported directly were used as NOEC values. Where an EC value for an effect between 10 and 20% was reported, a NOEC of half the EC value was taken. Effect levels greater than 20% were not used. Where results from different exposure periods were reported for the same study, the result from the longest available exposure matching the above criteria was taken. In one case, a NOEC and an EC10 value were presented for the same study and duration; in this case the geometric mean of the two values was used. The basic data are presented in Table VII.1. This includes the original values where the effect was between 10% and 20% (ie before division by two), and the values for different durations.

Toxicity of chromium (III) to soil processes (after Crommentuijn et al, 1997)

Process

Soil type

pH

% OM

%clay

Temp °C

Exposure

Endpoint

Result
(mg/kg dw)

Reference

Arylsulphatase

sand

7.7

1.6

2

20

18 m

EC10

2.1

Hanstra and Doelman, 1991

Sandy loam

5.1

5.7

9

20

6 w

EC10

(46)

18 m

EC10

1.0

Silty loam

7.4

2.4

19

20

18 m

EC10

83

clay

6.8

3.2

60

20

6 w

EC10

(43)

18 m

EC10

276

Sandy peat

3.0

12.8

5

20

6 w

EC10

(3338)

18 m

EC10

2730

Nitrification*

7.2

2

17

30

21 d

NOEC

100

Denneman and Van Gestel, 1990

N-mineralisation

5.8

4.4

23

30

20 d

EC20

260a

6.6

5

45

30

20 d

EC15

260a

7.8

6.4

30

30

20 d

EC13

260a

Phosphatase (acid)

Webster

5.8

4.4

23

37

1.5 h

NOEC

130

Juma and Tabatabai, 1977

Phosphatase (alkaline)

Okoboji

7.4

9.3

34

37

1.5 h

EC14

130a

Doelman and Haanstra, 1989

Phosphatase

sand

7.7

1.6

2

20

6 w

EC10

(1092)

18 m

EC10

723

Sandy loam

6

5.7

9

20

6 w

EC10

(2782)

18 m

EC10

858

Silty loam

7.4

2.4

19

20

6 w

EC10

(728)

18 m

EC10

280

clay

7.5

3.2

60

20

6 w

EC10

(52)

18 m

EC10

2153

Sandy peat

4.4

12.8

5

20

6 w

EC10

380

Respiration

Sandy loam

5.1

5.7

9

20

8 w

EC10

(5)

Denneman and Van Gestel, 1990

10 m

NOEC

(148)

10 w

EC10

(7)

43 w

EC10

6

Silty loam

7.4

2.6

19

20

21 m

EC10

86b

21 m

NOEC

182b

Sandy peat

4.3

12.8

5

20

19 m

EC10

71

clay

6.8

3.2

60

20

19 m

NOEC

400

Urease

sand

7.7

1.6

2

20

6 w

EC10

(1880)

Doelman and Haanstra, 1989

18 m

EC10

390

Silty loam

7.4

2.4

19

20

6 w

EC10

(2050)

18 m

EC10

890

Clay

7.5

3.2

60

20

18 m

EC10

350

Sandy peat

4.4

12.8

5

20

6 w

EC10

360

Harps

7.8

6.4

30

37

2 h

NOEC

26

Denneman and Van Gestel, 1990

Luton

6.8

7.4

30

37

2 h

EC17

260a

Okoboji

7.4

9.3

34

37

2 h

EC19

26a

Notes: All results basedon measured concentrations and on added amount of chromium. All involved addition of chromium (III) chloride except for * where chromium (III) sulphate was used.
( ): values in parentheses not used in the statistical extrapolation since a value from a longer exposure is available.
a: NOEC determined as ECx/2 as x=20 for use in the extrapolation.
b: geometric mean of the two values used in the extrapolation.

Validity criteria fulfilled:
not specified
Executive summary:

In the environment, it is likely that chromium (VI) will be reduced to chromium (III) in soil, and it is also likely that such conversion would have taken place in many of the toxicity tests. 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

Description of key information

From an EU review of studies to assess the impact of chromium (VI) and (III) on microbially-mediated soil processes a statistical assessment was carried out. A substantial amount of information is available for the toxicity of chromium (VI) to terrestrial organisms. In the environment, it is likely that chromium (VI) will be reduced to chromium (III) in soil, and it is also likely that such conversion would have taken place in many of the toxicity tests.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
5.9 mg/kg soil dw

Additional information

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. In this case it is considered that an assessment factor of 1 is sufficient, hence the PNEC for soil processes with chromium (III) is 5.9 mg/kg.