Diarsenic trioxide

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: ISO 18187

Version / remarks:

Contact test for solid samples using the dehydrogenase activity of Arthrobacter globiformis

Deviations:

no

GLP compliance:

no

Specific details on test material used for the study:

Na2HAsO4.7H2O

Analytical monitoring:

yes

Remarks:

background concentration and confirmation of nominal concentrations

Vehicle:

no

Details on preparation and application of test substrate:

Test substance added as aqueous solution and mixed with soil

Test organisms (inoculum):

other: Arthrobacter globiformis

Total exposure duration:

2 h

Remarks:

7 day equilibration after spiking prior to testing

Test temperature:

30

Moisture:

LUFA 2.2 - Dystric Cambisol: 20% of WHC
Refesol 05-G: 20% of WHC
Refesol 06-A: 20% of WHC
Ter Munck - Haplic Luvisol: 20% of WHC
Woburn - Dystric Cambisol: 20% of WHC
Zegveld - Histosol: 20% of WHC

Details on test conditions:

LUFA 2.2 - Dystric Cambisol: 1.78% OC
Refesol 05-G: 2.51% OC
Refesol 06-A: 2.75% OC
Ter Munck - Haplic Luvisol: 1% OC
Woburn - Dystric Cambisol: 5.1% OC
Zegveld - Histosol: 21.68% OC

Test in 24 well plates incubated in the dark for 2 h on a horizontal schaker (U=150/min) at a temperature of 30 ± 1 °C.

Nominal and measured concentrations:

Nominal concentrations in all test soils amounted to 0 (negative control), 30, 95 300, 949, and 3000 mg As/kg soil dry weight.
Measured As concentrations are within 20% of nominal values.

Reference substance (positive control):

yes

Remarks:

600 mg benzalkonium chloride/kg soil dry weight

Key result

Duration:

2 h

Dose descriptor:

NOEC

Effect conc.:

30 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: LUFA 2.2

Remarks:

Dystric Cambisol

Duration:

2 h

Dose descriptor:

other: LOEC

Effect conc.:

95 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: LUFA 2.2

Remarks:

Dystric Cambisol

Duration:

2 h

Dose descriptor:

EC10

Remarks:

EC10 < lowest test dose

Effect conc.:

13.4 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: LUFA 2.2

Remarks:

Dystric Cambisol

Duration:

2 h

Dose descriptor:

EC50

Effect conc.:

367.9 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: LUFA 2.2

Remarks:

Dystric Cambisol

Duration:

2 h

Dose descriptor:

NOEC

Effect conc.:

95 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Refesol 05-G

Duration:

2 h

Dose descriptor:

other: LOEC

Effect conc.:

300 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Refesol 05-G

Key result

Duration:

2 h

Dose descriptor:

EC10

Effect conc.:

103.5 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Refesol 05-G

Duration:

2 h

Dose descriptor:

EC50

Effect conc.:

431.9 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Refesol 05-G

Duration:

2 h

Dose descriptor:

other: LOEC

Effect conc.:

<= 30 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Refesol 06-A

Duration:

2 h

Dose descriptor:

EC10

Remarks:

EC10 < lowest test dose

Effect conc.:

4.9 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Refesol 06-A

Duration:

2 h

Dose descriptor:

EC50

Effect conc.:

289.9 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Refesol 06-A

Duration:

2 h

Dose descriptor:

NOEC

Effect conc.:

95 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Ter Munck

Remarks:

Haplic Luvisol

Duration:

2 h

Dose descriptor:

other: LOEC

Effect conc.:

300 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Ter Munck

Remarks:

Haplic Luvisol

Key result

Duration:

2 h

Dose descriptor:

EC10

Effect conc.:

40.9 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Ter Munck

Remarks:

Haplic Luvisol

Duration:

2 h

Dose descriptor:

EC50

Effect conc.:

555.3 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Ter Munck

Remarks:

Haplic Luvisol

Duration:

2 h

Dose descriptor:

NOEC

Effect conc.:

95 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Woburn

Remarks:

Dystric Cambisol

Duration:

2 h

Dose descriptor:

other: LOEC

Effect conc.:

300 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Woburn

Remarks:

Dystric Cambisol

Key result

Duration:

2 h

Dose descriptor:

EC10

Effect conc.:

112.6 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Woburn

Remarks:

Dystric Cambisol

Duration:

2 h

Dose descriptor:

EC50

Effect conc.:

983.2 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Woburn

Remarks:

Dystric Cambisol

Key result

Duration:

2 h

Dose descriptor:

NOEC

Effect conc.:

30 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Zegveld

Remarks:

Histosol

Duration:

2 h

Dose descriptor:

other: LOEC

Effect conc.:

95 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Zegveld

Remarks:

Histosol

Duration:

2 h

Dose descriptor:

EC10

Remarks:

EC10 < lowest test dose

Effect conc.:

10.1 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Zegveld

Remarks:

Histosol

Duration:

2 h

Dose descriptor:

EC50

Effect conc.:

460.2 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

other: dehydrogenase activity

Remarks on result:

other: Zegveld

Remarks:

Histosol

Reported statistics and error estimates:

Normality of the data:
checked with Kolmogorov-Smirnov or Shapiro-Wilk's test

Variance homogeneity of the data:
Levene's or Cochran test

NOEC and LOEC:
- In case data of normal distribution, homoscedasticity and a monotone dose-response relationship: Williams' Multiple Sequential t-test
- In case of normal distribution and variance heterogeneinty: one-sided Welch's t-test
- In case of normal distribution and homoscedasticity, but absence of a monotone relationship: Dunnett's t-test
- In case data were not normally distributed, but homoscedastic: Jonckheere-Terpstra test
- In case data were not normally distributed and heteroscedastic: Bonferroni U-test
- In case data were not normally distributed and the dose-response relationship was not monotone: Bonferroni Median test
(α = 0.05)

ECx values were determined with both linear and non-linear regression models
It was checked for the best fit (R2, Chi2, AIC) after performing an F-test to control significance of the dose response relationship

Validity criteria fulfilled:

yes

Conclusions:

The reliable 2-h EC10 or NOEC values for the effect of arsenic to the dehydrogenase activity of Arthrobacter globiformis ranged between 30.0 and 112.6 mg As/kg soil dry weight (based on added As concentrations in soil).
EC10 values were lower than the lowest test dose (30 mg As/kg soil dry weight) in three different soils and therefore their uncertainty was judged too high to consider these EC10 values for derivation of the PNEC.

Reference 2

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

ISO 14238

Deviations:

yes

Remarks:

soils not immediately used in the test after sampling

Qualifier:

according to guideline

Guideline:

OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)

Deviations:

no

GLP compliance:

no

Specific details on test material used for the study:

Na2HAsO4.7H2O

Analytical monitoring:

yes

Remarks:

background concentration and confirmation of nominal concentrations

Vehicle:

no

Details on preparation and application of test substrate:

Test substance added as aqueous solution and mixed with soil

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Remarks:

7 day equilibration after spiking prior to testing

Test temperature:

20

Moisture:

LUFA 2.2 - Dystric Cambisol: 47% of WHC
Refesol 05-G: 40% of WHC
Refesol 06-A: 30% of WHC
Ter Munck - Haplic Luvisol: 55% of WHC
Woburn - Dystric Cambisol: 45% of WHC
Zegveld - Histosol: 50% of WHC

Details on test conditions:

LUFA 2.2 - Dystric Cambisol: 1.78% OC
Refesol 05-G: 2.51% OC
Refesol 06-A: 2.75% OC
Ter Munck - Haplic Luvisol: 1% OC
Woburn - Dystric Cambisol: 5.1% OC
Zegveld - Histosol: 21.68% OC

Nominal and measured concentrations:

Nominal concentrations:
LUFA 2.2 - Dystric Cambisol: 0, 20, 63.3, 200, 632.5, and 2000 mg As/kg soil dry weight
Refesol 05-G: 0, 10, 31.6, 100, 316, and 1000 mg As/kg soil dry weight
Refesol 06-A: 0, 10, 31.6, 100, 316, and 1000 mg As/kg soil dry weight
Ter Munck - Haplic Luvisol: 0, 20, 63.3, 200, 632.5, and 2000 mg As/kg soil dry weight
Woburn - Dystric Cambisol: 0, 20, 63.3, 200, 632.5, and 2000 mg As/kg soil dry weight
Zegveld - Histosol: 0, 20, 63.3, 200, 632.5, and 2000 mg As/kg soil dry weight

Measured As concentrations are within 20% of nominal values.

Reference substance (positive control):

no

Duration:

28 d

Dose descriptor:

other: LOEC

Effect conc.:

<= 20 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

nitrate formation rate

Remarks on result:

other: LUFA 2.2

Remarks:

Dystric Cambisol

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

855.2 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

nitrate formation rate

Remarks on result:

other: LUFA 2.2

Remarks:

Dystric Cambisol

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

nitrate formation rate

Remarks on result:

other: Refesol 05-G

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

nitrate formation rate

Remarks on result:

other: Refesol 06-A

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 2 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

nitrate formation rate

Remarks on result:

other: Ter Munck

Remarks:

Haplic Luvisol

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 2 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

nitrate formation rate

Remarks on result:

other: Woburn

Remarks:

Dystric Cambisol

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 2 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

nitrate formation rate

Remarks on result:

other: Zegveld

Remarks:

Histosol

Key result

Duration:

28 d

Dose descriptor:

EC10

Effect conc.:

58.9 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

nitrate formation rate

Remarks on result:

other: Zegveld

Remarks:

Histosol

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

1 711.9 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

As (added dose)

Basis for effect:

nitrate formation rate

Remarks on result:

other: Zegveld

Remarks:

Histosol

Reported statistics and error estimates:

Normality of the data:
checked with Kolmogorov-Smirnov or Shapiro-Wilk's test

Variance homogeneity of the data:
Levene's or Cochran test

NOEC and LOEC:
- In case data of normal distribution, homoscedasticity and a monotone dose-response relationship: Williams' Multiple Sequential t-test
- In case of normal distribution and variance heterogeneinty: one-sided Welch's t-test
- In case of normal distribution and homoscedasticity, but absence of a monotone relationship: Dunnett's t-test
- In case data were not normally distributed, but homoscedastic: Jonckheere-Terpstra test
- In case data were not normally distributed and heteroscedastic: Bonferroni U-test
- In case data were not normally distributed and the dose-response relationship was not monotone: Bonferroni Median test
(α = 0.05)

ECx values were determined with both linear and non-linear regression models
It was checked for the best fit (R2, Chi2, AIC) after performing an F-test to control significance of the dose response relationship

Validity criteria fulfilled:

yes

Conclusions:

Regarding the effect of arsenic on the nitrifcation rate in six soils, a 28 d LOEC <= 23 mg As/kg soil dry weight was determined for LUFA 2.2 soil, whereas no effects were observed in the five other soils at concentrations up to 1000 or 2000 mg As/kg soil dry weight. Only one reliable EC10 value could be derived for the effect of arsenic on soil the nitrification rate in soil (58.9 mg As/L, based on added As concentrations in soil).

Description of key information

In total, 6 reliable EC₁₀ or NOEC values for chronic arsenic toxicity to soil microorganisms were retrieved from 1 published study report. All data were derived from soils amended with disodium hydrogen arsenate salts. These data cover effects on arsenic on nitrification and dehydrogenase activity in 6 different soils. The reliable NOEC and EC₁₀ values range between 30.0 and 112.6 mg As/kg dw (both values for dehydrogenase activity), expressed based on added elemental As concentrations in soil. All reliable NOEC and EC₁₀ values were taken forward to the derivation of the PNEC according to the statistical extrapolation approach.

In addition, unbounded NOEC values of 52.8 mg As/kg soil (total soil concentration) were retrieved for the long-term effect of arsenic on the soil microbial biomass, ATP content, dehydrogenase activity and nitrification in a sandy cambisol contaminated for 9 years with sodium arsenic salts.