Reaction mass of chromium (+ 3) hydroxide sulfate and sodium sulfate

Toxicity to soil microorganisms

Link to relevant study record(s)

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	260^a
		6.6	5	45	30	20 d	EC15	260^a
		7.8	6.4	30	30	20 d	EC13	260^a
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	130^a	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	86^b
						21 m	NOEC	182^b
	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	260^a
	Okoboji	7.4	9.3	34	37	2 h	EC19	26^a

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.