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Bioaccumulation: terrestrial

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Endpoint:
bioaccumulation: terrestrial
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Non-guideline field study, well performed and with acceptable documentation. Valuable data on chromium bioaccumulation in different earthworm species under field conditions (including Cr concentrations ranging from 4.9 to 71 mg Cr/kg) is presented.
Qualifier:
no guideline available
Principles of method if other than guideline:
The study investigated the accumulation of 7 elements including chromium from different earthworm species in 20 diverse sites in the USA including natural sites, mining sites, industrial sites and sites close to galvanized towers. Chromium concentrations in soil and earthworms were assessed using AAS (atomic absorption spectrophotometer).
GLP compliance:
no
Radiolabelling:
no
Remarks:
field study
Details on sampling:
Four classes of study sites were defined: natural (Nat.), mining (Min.), industrial (Ind.), and galvanized towers (Tow.)

Soil analysis
For detailed site characteristics (Type, pH, % organic matter, concentrations of macroelements), please refer to table 1. Sampled areas varied between 10 m2 and 100 m2. Composite soil samples (n = 15) were taken close to holes were earthworms were found down to a depth of 15 cm. Soil samples were sieved (2mm) and analysed for pH, P, Ca, Mg and K by the Pennsylvania State University soil laboratory. A second soil subsample was frozen and later analysed by the Patuxent Wildlife Research Center (PWRC) for Pb, Cu, Zn, Cd, Cr and Se analysis.

Earthworm analysis:
Earthworms were dug with a spade, rinsed with distilled water , refrigerated for three days on a moist paper towel and then separated by species. The earthworms were subsequently killed in boiling water, cut into 1-3 cm sections and their alimentary canals were flushed with distilled water using a needle. Samples were put into acid-washed glass jars, frozen, and sent to PWRC for elemental analysis.
Test organisms (species):
other: Different earthworm species found in the field, see below:
Details on test organisms:
Sampled earthworm species:
Aporrectodea tuberculata
Aporrectodea longa
Aporrectodea trapezoides
Aporrectodea turdiga
Eisenoides carolinensis
Eisenoides lonnbergi
Lumbricus rubellus
Lumbricus terrestris
Sparganophilus eiseni
Test temperature:
field study
pH:
See table 1: pH range 4.2 to 7.2
TOC:
See table 1.
Nominal and measured concentrations:
Soil field chromium concentrations: see table 2.
Type:
BSAF
Value:
< 1 dimensionless
Basis:
whole body d.w.
Remarks on result:
other:
Remarks:
BSAF (6 species) based on 14 samples from industrial sites
Type:
BSAF
Value:
< 1 dimensionless
Basis:
whole body d.w.
Remarks on result:
other:
Remarks:
BSAF (5 species) based on 9 samples from natural sites
Type:
BSAF
Value:
< 1 dimensionless
Basis:
whole body d.w.
Remarks on result:
other:
Remarks:
BSAF (5 species) based on samples from 8 mining sites
Type:
BSAF
Value:
2.6 dimensionless
Basis:
whole body d.w.
Remarks on result:
other:
Remarks:
BSAF (1 species) based on samples from 4 sites close to galvanized towers
Details on results:
Metal concentrations in earthworms were poorly correlated with soil elemental concentrations. Chromium correlation coefficient: -0.14
Based on the chromium concentrations in soil and earthworms, BSAF (biota-to-soil accumulation factor) values could be derived with a median BSAF of <1 for all sites investigated. Therefore, the terrestrial bioaccumulation of chromium in the different earthworm species investigated in this study, is low.

Table 2: Chromium concentrations in soil and earthworms (d.w.) and derived BSAF

Chromium concentration in Earthworms mg/kg

Soil Chromium mg/kg

BSAF

Nat. A

Eisenoides carolinensis (c)

t

7.8

<1

Nat. B

E. loennbergi (c)

t

11

<1

Nat. B

Lumbricus rubellus (c)

1.2

11

0.1

Nat. C

E. loennbergi (c)

14

16

0.9

Nat. D

E. loennbergi (c)

16

11

1.5

Nat. E

Aporrectodea turgida (c)

1.8

4.9

0.4

Nat. F

E. loennbergi (c)

2.1

14

0.2

Nat. F

E. loennbergi (a)

t

14

<1

Nat. G

Sparganophilus eiseni (c)

t

19

<1

Min. A

L. terrestris (a)

6.0

71

0.1

Min. B

A. tuberculata (c)

13

24

0.5

Min. B

A. longa (c)

t

24

<1

Min. C1

Pheretima sp. (c)

t

7.7

<1

Min. C2

L. terrestris (c)

27

10

2.7

Min. C2

A. tuberculata (a+c)

t

10

<1

Min. C3

L. terrestris (a + c)

11

6.4

1.7

Min. C4

L. terrestris (a)

t

10

<1

Ind. A

Aporrectodea spp. (c)

12

30

0.4

Ind. B

L. terrestris (a)

1.8

30

0.1

Ind. C

A. longa (c)

6.0

30

0.2

Ind. D

A. trapezoides (c)

11

30

0.4

Ind. D

A. trapezoides (a)

2.1

12

0.2

Ind. E

A. trapezoides (c)

20

51

0.4

Ind. E

A. trapezoides (a)

3.6

51

0.1

Ind. F1

A. longa (c)

4.9

16

0.3

Ind. F2

A. longa (c)

1.3

15

0.1

Ind. F2

A. tuberculata (c)

53

15

3.5

Ind. G

L. rubellus (c)

22

32

0.7

Ind. G

A. trapezoides (c)

8.4

32

0.3

Ind. H1

A. trapezoides (c)

26

9.3

2.8

Ind. H2

A. trapezoides (c)

9.8

10

1

Tow. A

E. loennbergi (a)

39

10

3.9

Con. A

E. loennbergi (a)

15

11

1.4

Tow. B

E. loennbergi (c)

51

9.5

5.4

Con. B

E. loennbergi (a)

12

9.7

1.2

Validity criteria fulfilled:
not applicable
Conclusions:
In the present study the accumulation of chromium in different earthworm species was investigated in a field experiment covering a wide range of species and soil conditions (including Cr concentrations ranging from 4.9 to 71 mg/kg). Based on the chromium concentrations in soil and earthworms, BSAF (biota-to-soil accumulation factor) values could be derived with a median BSAF of <1 for all sites investigated. Therefore, the terrestrial bioaccumulation of chromium in the different earthworm species investigated in this study, is low.
Endpoint:
bioaccumulation: terrestrial
Type of information:
experimental study
Adequacy of study:
disregarded due to major methodological deficiencies
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: see 'Remarks'
Remarks:
Hydroponic assays are not a relevant route of exposure for the assessment of terrestrial bioaccumulation. Feeding studies performed in this study provide valuable insights on chromium mobility with regard to secondary poisoning. However, due to several methodological shortcomings and insufficient documentation (see below), the study is included for informational purpose only.
Qualifier:
no guideline followed
Principles of method if other than guideline:
The study investigated chromium uptake and distribution in bean (Phaseolus vulgaris) and wheat (Triticum aestivum) based on hydroponic assays with chromium-51-labelled Cr(III) and Cr(VI) substances. In addition, the absorption of chromium by rats was investigated in feeding studies.
GLP compliance:
no
Radiolabelling:
yes
Details on sampling:
Plants were harvested, separated into seeds, chaff/pods, leaves, stem and roots. Plant tissues were freeze-dried except bean seeds and wheat plant tops. Plant tissues were pulverized and subsequently sieved.
Vehicle:
not specified
Details on preparation and application of test substrate:
Plant culture: Plants were grown in purified (chromium-free, <0.02 ppb Cr) nutrient solution (no details given). Application of radiochromium solution at flowering stage (bean) and boot stage (wheat) for a total of 22 days. Treatments were added every other day for a total of seven additions. On day 22, 9 days after final treatment, the solution was sampled and replaced by standard, Cr-free nutrient solution.

Radiochromium treatment:
Stock chromium solution, radiolabelled: 51CrCl3 (New England Nuclear, Boston, USA) was added to 2.5 mL of a 200 µg Cr/mL CrCl3 working solution which was further diluted to a final concentration of 10 µg Cr/mL
Cr(VI) solution, radiolabelled: 2 mL of Cr stock solution and 0.8 mL 0.1 N acetic acid were added to the nutrient solution.
Cr(III) solution, radiolabelled: 2 mL of Cr stock solution and 0.8 mL 0.1 N acetic acid were mixed in a vial and reduced with 0.6 mL of 0.001 M ascorbic acid. The solution was then added to the nutrient solution
Test organisms (species):
other: Phaseolus vulgaris, Triticum aestivum
Details on test organisms:
Phaseolus vulgaris: 40 day growth period (18d depuration)
Triticum aestivum: 50 day growth period (22d depuration)
Total exposure / uptake duration:
22 d
Total depuration duration:
> 18 - < 28 d
Test temperature:
no data
pH:
no data
TOC:
no data
Moisture:
no data
Nominal and measured concentrations:
no, only relative activity levels remaining in the solution after final treatment. No distinction between solved, precipitated and adsorbed chromium.

Results:

- there was little difference in the uptake of 51Cr from the Cr(VI) or Cr(III) source

- bean plants contained an average of 55% of the total 51Cr added, whereas wheat plants contained on average 81% of added 51Cr.

- 51Cr was strongly bound to roots for both wheat and beans (>91.5% of total Cr applied found on root)

- translocation to aboveground tissues in both species was low (< 7% in bean leaves, <1.5% in wheat leaves)

The results, however, are not considered reliable for risk assessment due to several methodological shortcomings and insufficient documentation, i.e. plant age not reported, exposure concentrations (total Cr concentrations applied) not reported, chemical form of Cr in the nutrient solution is not known, pH not reported, Cr concentration used in the nutrient solution was “selected to be nontoxic”, is however not reported and toxicity-thresholds as cited by the authors are exceeded, mesh size for sieving of plant material not reported, plant toxicity effects not reported. In addition, hydroponic exposure is not a relevant route of exposure for the assessment of terrestrial bioaccumulation in plants.

Absorption of Plant Cr by rats:

 

Table: Chromium remaining in rats at various times after feeding bean leaf tissue with incorporated 51Cr or inorganic 51Cr

Treatment

4h

12h

24h

48h

72h

51Cr bean

100

55.6

1.9

<0.5

<0.5

(CrO2)2-

100

41.5

1.1

<0.5

<0.5

After 48h, <0.5% of the total chromium applied remained in rats, however >95% of the initial activity was found in the fecal samples. Organ and tissue samples showed less than 0.2% of the initial dose. Therefore, absorption of 51chromium was low. Total applied chromium concentrations are however not reported, therefore results can not be considered reliable.

Validity criteria fulfilled:
no
Conclusions:
Due to several methodological shortcomings and insufficient documentation the results on plant chromium bioaccumulation cannot be considered reliable and are included for informational purposes only. The feeding experiments with organic and anorganic radiolabelled chromium performed in this study do however give valuable insights on chromium mobility with regard to secondary poisoning. After 48h, <0.5% of the total chromium applied remained in rats and >95% of the initial activity was found in the fecal samples, pointing to a low potential for chromium accumulation through the food chain. Total applied chromium concentrations are however not reported and results should therefore be considered with caution.
Endpoint:
bioaccumulation: terrestrial
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
3 weeks
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Although no published guideline was followed, and not all experimental procedures and parameters were reported, the experimental description in the paper is clear and convincing.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Earthworms were exposed to moderately contaminated soils collected from field sites in the Netherlands. The exposure period was 3 weeks and it was assumed that by this time an equilibrium between soil and the earthworm body had been established. A control was carried out using an uncontaminated OECD artificial soil. Worm tissue samples were analysed for metal concentrations, including Cr, using graphite furnace atomic absorption spectroscopy.
GLP compliance:
no
Specific details on test material used for the study:
Soils with moderate metal contamination, including chromium. Details in ET&C (1997)16/12): 2479 – 2488.
Radiolabelling:
no
Details on sampling:
- Sampling intervals/frequency for test organisms: Initial body weights and final body weights (after 3 weeks) were measured
- Sampling intervals/frequency for test medium samples: Initial soil pH and final soil pH (after 3 weeks) was measured
- Sample storage conditions before analysis: After exposure, earthworms were left overnight on humid filter paper, frozen, lyophilized and dismembered.
- Details on sampling and analysis of test organisms and test media samples (e.g. sample preparation, analytical methods):
Soil - CaCl2 extraction (0.01M) and digestion with nitric acid (reported in Environ. Toxicol. Chem. 16: 2470-2478).
Earthworms - Deionised water, nitric acid and concentrated hydrochloric acid was added to the sample and digested in a microwave oven (1h, 630W). Resultant sample was diluted with deionized water and filtered (0.45 µm). Cr was measured with graphite furnace atomic absorption spectroscopy.
Vehicle:
not specified
Details on preparation and application of test substrate:
Test material not applied directly to soils, instead field soils moderately contaminated with chromium were collected from field sites in the Netherlands. Full details reported in Environ. Toxicol. Chem. 16: 2470-2478.
Test organisms (species):
other: Eisenia andrei
Details on test organisms:
TEST ORGANISM
- Common name: Red tiger worm
- Source: Cultures kept for many generations at 20ºC
- Age at test initiation (mean and range, SD): Adults originating from cocoons produced 21-24 weeks before study initiation.
Total exposure / uptake duration:
3 wk
Test temperature:
20ºC
pH:
The pH of soils ranged from 3.02 to 7.02 and maximum deviations from initial values were -0.5 and +0.4 pH units. The artificial soil had a slightly higher pH increase of 0.7 units.
TOC:
Not reported.
Moisture:
Not reported.
Details on test conditions:
TEST SYSTEM
- Test container (material, size): 1 L glass jars
- Amount of soil or substrate: 1 kg fresh weigh of soil
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: Not stated
- No. of replicates per control / vehicle control: Not stated

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): Netherlands (See Environ. Toxicol. Chem. 16: 2470-2478)

OTHER TEST CONDITIONS
- Adjustment of pH: Not adjusted
- Photoperiod: Constant illumination

Nominal and measured concentrations:
Reported in Environ. Toxicol. Chem. 16: 2470-2478.
Type:
BCF
Value:
0.03 - 0.53 dimensionless
Basis:
whole body d.w.
Time of plateau:
3 wk
Kinetic parameters:
Not stated.
Metabolites:
Not stated.
Details on results:
- Mortality of test organisms: In some soils one or two dead individuals were observed. In one soil almost all test organisms died. This was excluded for the analysis.
- Behavioural abnormalities: None reported.
- Observations on body length and weight: Maximum weight gain was 70-80% in one soil and maximum weight loss was 35-50% in two soils.
- Mortality and/or behavioural abnormalities of control: None reported.
- Loss of test substance during test period: Not reported.
Reported statistics:
Statistics were carried out according to those reported in Environ. Toxicol. Chem. 16: 2470-2478.

Table1– Body concentrations and bioconcentration factors for Eisenia andrei following 3 weeks of exposure to 20 contaminated field soils

Sample

pH

Body concentration of Cr

(mmol/kg dry weight)

BCF

A

3.42

0.11

0.53

B

5.67

0.08

0.09

C

5.35

0.09

0.07

D

7.17

0.09

0.19

E

6.53

0.06

0.13

F

6.51

0.05

0.08

G

6.80

0.12

0.06

H

3.54

0.02

0.10

I

3.02

BD

ND

J

4.98

0.03

0.06

K

3.77

ND

ND

L

6.83

ND

ND

M

3.82

0.03

0.12

N

3.85

0.02

0.03

O

5.26

0.10

0.10

P

6.75

0.33

0.19

Q

6.69

0.08

0.08

R

6.89

0.36

0.09

S

7.02

0.11

0.10

T

6.95

0.11

0.12

BD = concentrations below detection limit for both replicates

ND = not determined

Validity criteria fulfilled:
no
Remarks:
Study not conducted to established test guidelines. Please refer to ‘Rationale for reliability incl. deficiencies’.
Conclusions:
Chromium BCFs showed some variability among soils but were low, with BCFs ranging from 0.03 to 0.53. The authors investigated the role of soil characteristics in moderating uptake and suggested that soil characteristics do not appear to affect the uptake of chromium. However, the concentrations of chromium present in the soil during the exposure period was not reported here but in Environ. Toxicol. Chem. 16: 2470-2478 and also the speciation of chromium in these soils was unknown.
Executive summary:

Earthworms were exposed to moderately contaminated soils containing chromium for 3 weeks in a non-standard study. 20 soils were collected from field sites in the Netherlands and the soil characterisation was reported in Environ. Toxicol. Chem. 16: 2470-2478. 10 adult earthworms (Eisenia andrei) were exposed to each soil type and to one control (OECD artificial soil). Earthworm behaviour in exposed soils was judged with respect to behaviour in the control soil. Earthworms were exposed for 3 weeks and it was assumed that by this time an equilibrium between soil and the earthworm body had been established. Initial and final (fresh) body weights were measured and earthworm tissue samples were analysed for metal concentrations, including chromium, using graphite furnace atomic absorption spectroscopy.

Chromium BCFs showed some variability among soils but were low, with BCFs ranging from 0.03 to 0.53. The authors investigated the role of soil characteristics in moderating uptake and suggested that soil characteristics do not appear to affect the uptake of chromium. However, the concentrations of chromium present in the soil during the exposure period was not reported here but in Environ. Toxicol. Chem. 16: 2470-2478 and also the speciation of chromium in these soils was unknown. It was reported in the EU RAR that the negative dependence of Kpsoil on dissolved organic carbon seen in Environ. Toxicol. Chem. 16: 2470 -2478, was typical of chromium (III) species rather than chromium (VI) oxyanions. 

Endpoint:
bioaccumulation: terrestrial
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Non-guideline field study, well performed with minor deficiencies regarding methodological documentation. No raw data is presented on chromium soil concentrations and concentrations in earthworm tissue, no data on detection limits and/or element recoveries presented. However provides valuable data on chromium bioaccumulation under field conditions.
Qualifier:
no guideline available
Principles of method if other than guideline:
The study investigates accumulation and toxic effects of heavy metals towards earthworms in laboratory and field experiments using different types of agricultural soils treated with municipal waste compost. Chromium concentrations in soils and worm tissue were analysed via AAS (atomic absorption spectrometry)
GLP compliance:
not specified
Radiolabelling:
no
Details on sampling:
Earthworm sampling:
Earthworms were sampled by digging and hand sorting of the top 20cm layer of a field plot with 6 different types of agricultural soils, which had been annually treated with municipal waste compost over the past decade. Worms were allowed to void their guts prior to analysis.

Soil types:
Three loamy soils and three sandy soils were chosen for sampling:
Soil A: 30% clay; Soil B: 10% clay; Soil C: riverine clay loam with 40% clay; Soil D: peaty sand with 10% humus in top layer; Soil E: reclaimed sandy podzolized soil with 7% humus; Soil F: Plaggen soil with 3% humus
Soil samples were collected from the top 20cm, air-dried and passed through a 2 mm sieve before analysis. For detailed soil characteristics, please refer to table 1-2 (any other information on materials and methods incl. tables, below)
Vehicle:
no
Test organisms (species):
other: Allolobophora caliginosa
Test temperature:
n/a
pH:
please refer to table 1-2.
TOC:
please refer to table 1-2.
Moisture:
no data
Details on test conditions:
For CEC in meq/100g, please please refer to table 1-2. Each soil type was divided by concrete slabs into sub-plots of 1 x 1 x 1 m, with the original profile of each soil type present to a depth of one metre. Soils were then mixed with compost into the top 20 cm at rates of 0, 20 and 40 t ha-1 y-1 in four replicates (see table 1-2 below). During the sampling, soils were sown with perennial ryegrass.
Type:
BSAF
Value:
0.08 dimensionless
Basis:
whole body d.w.
Calculation basis:
steady state
Remarks on result:
other:
Remarks:
Median BSAF for A. caliginosa (n=18) based on six different soils (each with three different levels of compost addition, see table 1-2)
Details on results:
- Annual treatment with municipal waste compost did not exert a significant positive or negative influence on earthworm numbers. However, earthworm numbers were dependent on soil type.
- chromium concentration in adults and sub-adults: no significant differences between adult and sub-adult worms were found
- Cr concentrations in soil ranged from approx. 15 mg/kg to approx. 130 mg/kg (only graphical presentation)
- chromium was hardly accumulated in earthworms and behaved similar in all soils, showing he lowest concentration factors of all elements investigated (Cr, Mn, Fe, Ni, Pb, Cu, Zn, Cd)
- A. caliginosa was found in all investigated soils and was therefore used for comparative assessment of concentration factors
- For A. caliginosa concentration factors (= biota-soil accumulation factors, BSAF), i.e. the ratio of worm metal concentration in mg/kg to soil metal concentration in mg/kg, please refer to table 3 (any other information on results incl. tables).

Table 3. A. caliginosa concentration factors / BSAF for chromium in six different soil type amended with municipal waste compost. 1 = untreated control; 2 = 20 t ha-1 y-1; 3= 40 t ha-1 y-1

Soil

Cr

A1

0.01

A2

0.03

A3

0.07

B1

0.11

B2

0.10

B3

0.15

C1

0.03

C2

0.02

C3

0.07

D1

0.08

D2

0.03

D3

0.10

E1

0.09

E2

0.03

E3

0.13

F1

0.00

F2

0.11

F3

0.13

Median

0.08

Based on A. caliginosa chromium concentrations and the respective chromium soil concentrations in six different soils (representing different levels of municipal waste amendment), a median BSAF of 0.08 can be derived.

Validity criteria fulfilled:
not applicable
Conclusions:
In the present study the accumulation of chromium in the earthworm species A. caliginosa was investigated in a field experiment. Based on the chromium concentrations in soil and earthworms, BSAF (biota-to-soil accumulation factor) values could be derived ranging from 0.01 to 0.15 (median BSAF = 0.08). Therefore, the terrestrial bioaccumulation of chromium is low.
Endpoint:
bioaccumulation: terrestrial
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Non-guideline field study, well performed and with acceptable documentation. Provides valuable data on chromium bioaccumulation under field conditions
Qualifier:
no guideline followed
Principles of method if other than guideline:
The study investigated metal concentrations in two earthworm species derived from two sewage sludge-amended former mining and non-mined soils. The Concentrations of twelve elements including chromium were assessed in soil samples and earthworm tissue using AAS (atomic absorption spectroscopy).
GLP compliance:
no
Radiolabelling:
no
Details on sampling:
Two sewage sludge application fields representative of minesoil and nonmined areas and two nonamended fields representative of minesoil and nonmined areas were selected for earthworm sampling:
Minesoil 3: 174 t of cumulative added sludge (1974-1977) applied, pH 7.5
Minesoil 6: no sludge applied, pH 7.9
Soil 21: Ipava silt loam (aquic argiudolls), 188 t of cumulative added sludge (1974-1977) applied, pH 5.9
Soil 110: Lawson silt loam (cumulic hapludolls); no sludge applied, pH 8.0

For the elemental composition of the applied sewage sludge, please refer to table 1 (any other information on materials and methods incl. tables, below)

Earthworm sampling:
Earthworms were obtained by digging up soil down to a depth of 20 cm. Paired sets of worm samples were collected. Worms were washed with deionized water, placed in polyethylene chambers lined with moist paper towels and allowed gut evacuation for 6 to 8 days at 23 °C. Subsequently, worms were dried at 105 °C for 24h in acid digestion tubes and wet and dry weights were determined.
Test organisms (species):
other:
Details on test organisms:
Lumbricus terrestris and Aporrectodea tuberculata
Test temperature:
field study
pH:
Minesoil 3: pH 7.5
Minesoil 6: pH 7.9
Soil 21: Ipava silt loam (aquic argiudolls) pH 5.9
Soil 110: Lawson silt loam (cumulic hapludolls) pH 8.0
Details on test conditions:
Worms were allowed gut evacuation for 6 to 8 days at 23 °C
Type:
BSAF
Value:
0.05 dimensionless
Basis:
whole body d.w.
Calculation basis:
steady state
Remarks on result:
other:
Remarks:
Minesoil, nonamended; Mean factors derived from 6 sampling dates, SD: 0.05
Type:
BSAF
Value:
0.08 dimensionless
Basis:
whole body d.w.
Calculation basis:
steady state
Remarks on result:
other:
Remarks:
Minesoil, amended; Mean factors derived from 6 sampling dates, SD: 0.11
Type:
BSAF
Value:
0.04 dimensionless
Basis:
whole body d.w.
Calculation basis:
steady state
Remarks on result:
other:
Remarks:
Nonmined soil, nonamended; Mean factors derived from 6 sampling dates, SD: 0.02
Type:
BSAF
Value:
0.06 dimensionless
Basis:
whole body d.w.
Calculation basis:
steady state
Remarks on result:
other:
Remarks:
Nonmined soil, nonamended; Mean factors derived from 6 sampling dates, SD: 0.05

Soil chromium concentrations ranged from 12 to 73 mg Cr/kg, whilst earthworm chromium concentrations ranged from 0.1 to 8.8 mg Cr/kg. Means of six samplings are given in table 2 below. Metal enrichment ratios (chromium concentrations in worms/ chromium concentrations in soil for six sampling dates), i.e. biota-soil-accumulation factors, were determined for each soil type, both for amended and non-amended soils (for composition of amended sludge, please refer to table 1):

BSAF (Minesoil, nonamended): 0.05±0.05, BSAF (Minesoil, amended): 0.08±0.11

BSAF (Nonmined, nonamended): 0.04±0.02, BSAF (Nonmined, amended): 0.06±0.05

Table 2: Chromium concentrations in soils an earthworms (mg/kg d.w.)

 

 

Nonamended

Sludge amended

Minesoil

Soil

23 ± 1.5

38 ± 11

 

Earthworms

1.2 ±1.2

2.3 ± 2.6

Nonmined Soil

Soil

18 ± 3.5

45 ± 20

 

Earthworms

0.6 ± 0.4

2.6 ± 3.2

Validity criteria fulfilled:
not applicable
Conclusions:
In the present study the accumulation of chromium in different earthworm species was investigated in a field experiment. Based on the chromium concentrations in soil and earthworms, BSAF (biota-to-soil accumulation factor) values could be derived ranging from 0.04 to 0.08. Therefore, the terrestrial bioaccumulation of chromium in the different earthworm species investigated in this study, is low.
Endpoint:
bioaccumulation: terrestrial
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
6 weeks
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was not conducted according to an established guideline and some experimental procedures and parameters were not reported. However, the paper describes the work reasonably thoroughly and the results are consistent with other reported work.
Principles of method if other than guideline:
This study was not carried out to a test guideline. Earthworms were incubated in untreated artificial soil for 1 week, then exposed to the test material for 3 weeks and then transferred to untreated artifical soil for a 3 week recovery period. Soil samples were taken and analysed at the start and end of the 3 week exposure period. Elimination rates were determined by analysing worms at the end of the recovery period.
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not stated.
Radiolabelling:
no
Details on sampling:
- Sampling intervals/frequency for test organisms: Elimination rates were determined at the end of the 3 week recovery period
- Sampling intervals/frequency for test medium samples: At the start and the end of the 3 week exposure period
- Sample storage conditions before analysis: Earthworms were incubated on wet filter paper in the dark at 15C for 48 hours. After 24 hours filter paper was renewed.
- Details on sampling and analysis of test organisms and test media samples (e.g. sample preparation, analytical methods): Soil and earthworm samples were digested in HNO3 at 180C for 16 hours and analysed by ICP-AES and AAS respectively.
Vehicle:
no
Details on preparation and application of test substrate:
Non standard guideline outlined in Ecotox. Environ Saf, 23: 206-220 (1992).
Test organisms (species):
other: Eisenia andrei
Details on test organisms:
TEST ORGANISM
- Common name: Redworm
- Source: Laboratory culture
- Age at test initiation (mean and range, SD): Ranged between 9.5 and 15.5 weeks

ACCLIMATION
- Acclimation period: 1 week
- Acclimation conditions (same as test or not): Artificial soil (test soil)
Total exposure / uptake duration:
3 wk
Total depuration duration:
3 wk
Test temperature:
Not stated.
pH:
Not stated.
TOC:
Not stated.
Moisture:
Not stated.
Details on test conditions:
TEST SYSTEM
Non standard guideline outlined in Ecotox. Environ Saf, 23: 206-220 (1992)
SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
Artificial soil used, properties not stated.
Nominal and measured concentrations:
Test material was applied at 0, 10, 32, 100, 320, 1000 mg Cr/kg dry soil.
Type:
BCF
Value:
0.031 - 0.047 dimensionless
Basis:
not specified
Remarks on result:
other: Dose rate 10 -100 mg Cr/kg dry soil
Type:
BCF
Value:
0.016 - 0.019 dimensionless
Basis:
not specified
Remarks on result:
other: Dose rate 320 - 1000 mg Cr/kg dry soil
Type:
BCF
Value:
0.048 dimensionless
Basis:
not specified
Remarks on result:
other: Control soil (6.3 mg Cr/kg dry weight
Elimination:
yes
Parameter:
DT50
Depuration time (DT):
7 d
Elimination:
yes
Parameter:
DT50
Depuration time (DT):
109 d
Kinetic parameters:
Not stated.
Metabolites:
Not stated.
Details on results:
Growth was significantly reduced at 100 mg Cr/kg dry soil.
Reported statistics:
Not stated
Validity criteria fulfilled:
no
Remarks:
Study not conducted to established test guidelines. Please refer to ‘Rationale for reliability incl. deficiencies’.
Conclusions:
Chromium levels in worms at the highest dose levels (100, 300 and 1000 mg Cr/kg dry soil) were significantly increased compared to controls, demonstrating a dose related increase. In the exposed worms concentrations ranged between 0.8 and 18 mg Cr/kg dry weight at the lowest and highest exposure level respectively whereas control worms had a chromium concentration of 0.3 mg Cr/kg dry weight.
Reported BCF values for the accumulation of chromium in the worms were 0.031-0.047 at the three lowest dose levels (10, 32, 100 mg Cr/kg dry soil) and 0.016-0.019 at the two highest dose levels (320 and 1000 mg Cr/kg dry soil). The control soil had a BCF value of 0.048 which corresponded to 6.3 mg Cr/kg dry weight. Chromium levels returned to normal for all dose groups (0.3 and 1.1 mg Cr/kg dry weight) after 3 weeks. It was concluded that chromium was eliminated from the earthworms with half life times of 51-109 days for the two lowest dose groups and of 5-7 days for the three highest dose groups.
Executive summary:

The accumulation and elimination of chromium by the earthworm Eisenia andrei was determined in an artificial soil in a non standard study. Earthworms were exposed to 5 concentrations (10 - 1000 mg Cr/kg dry soil) of chromium (III) nitrate for 3 weeks. The earthworms were then transferred to an untreated artificial soil for a 3 week recovery period. Elimination rates were determined by analysing the earthworms at the end of the recovery period.

Chromium levels in worms at the highest dose levels (100, 300 and 1000 mg Cr/kg dry soil) were significantly increased compared to controls, demonstrating a dose related increase. In the exposed worms concentrations ranged between 0.8 and 18 mg Cr/kg dry weight at the lowest and highest exposure level respectively whereas control worms had a chromium concentration of 0.3 mg Cr/kg dry weight.

Reported BCF values for the accumulation of chromium in the worms were 0.031-0.047 at the three lowest dose levels (10, 32, 100 mg Cr/kg dry soil) and 0.016-0.019 at the two highest dose levels (320 and 1000 mg Cr/kg dry soil). The control soil had a BCF value of 0.048 which corresponded to 6.3 mg Cr/kg dry weight. The bioaccumulation of chromium (III) in these earthworms can be considered as negligible.

Chromium levels returned to normal for all dose groups (0.3 and 1.1 mg Cr/kg dry weight) after 3 weeks. It was concluded that chromium was eliminated from the earthworms with half life times of 51-109 days for the two lowest dose groups and of 5-7 days for the three highest dose groups.

Description of key information

Nine studies on the bioaccumulation of chromium (III) and total chromium concentrations in terrestrial organisms are available, including laboratory and field studies. Based on a weight of evidence approach using data of terrestrial bioaccumulation in different earthworm and plant species including field data, the terrestrial bioaccumulation of chromium(III) is considered to be negligible. Furthermore, measured BSAFs seem to be inversely related to soil concentrations indicative of active regulation, as typically observed for metals.

Key value for chemical safety assessment

Additional information

The accumulation and elimination of chromium by the earthworm Eisenia andrei was determined in an artificial soil (van Gestel et al, 1993). Earthworms were exposed to 5 concentrations (10 - 1000 mg Cr/kg dw) of chromium (III) nitrate for 3 weeks. The earthworms were then transferred to an untreated artificial soil for a 3-week recovery period. Elimination rates were determined by analysing the earthworms at the end of the recovery period. Chromium levels in worms at the highest dose levels (100, 300 and 1000 mg Cr/kg dw) were significantly increased compared to controls, demonstrating a dose related increase. In exposed worms, concentrations ranged from 0.8 to 18 mg Cr/kg dry weight at the lowest and highest exposure level, respectively, whereas a chromium concentration of 0.3 mg Cr/kg dw was measured in control worms. Reported BAF values range from 0.031 to 0.047 at the three lowest levels (10, 32, 100 mg Cr/kg dw) and from 0.016 to 0.019 at the two highest levels (320 and 1000 mg Cr/kg dry soil). The highest BSAF, a BSAF of 0.048, is reported for control worms at a background concentration of 6.3 mg Cr/kg dw. Thus, bioaccumulation of chromium (III) in earthworms can be considered as negligible. Measured BSAFs seem to be inversely related to soil concentrations indicative of active regulation, as typically observed for metals. Chromium levels returned to normal for all dose groups (0.3 and 1.1 mg Cr/kg dry weight) after 3 weeks. It was concluded that chromium was eliminated from the earthworms with a half-life of 51-109 days for the two lowest dose groups and of 5-7 days for the three highest dose groups.

Janssen et al (1997) exposed earthworms for 3 weeks to 20 different soils moderately contaminated with chromium. Soils were collected from field sites in the Netherlands and 10 adult earthworms (Eisenia andrei) were exposed to each soil and to one control (OECD artificial soil), respectively. Chromium BSAFs varied among soils but were generally low, ranging from 0.03 to 0.53. Soil characteristics do not appear to affect the uptake of chromium.

Pietz et al. (1984) assessed the accumulation of chromium by earthworms in former mining sites and non-mined soil to which sewage sludge containing chromium was added (12 to 73 mg Cr/kg dw). Based on six sampling dates each, four sampled sites, BSAF values ranging from 0.04 to 0.08 in Lumbricus terrestris and Aporrectodea tuberculate were reported.

Similar results were obtained in a field study carried out by Ma et al. (1982) investigating the accumulation of total chromium in the earthworm Aporrectodea caliginosa exposed to different agricultural soils treated with municipal waste compost. Based on six different soil types (pH range 4.7-7.1, OM content 2.8-13.6 % w/w), each with three different levels of compost addition and chromium concentrations ranging from 15 to 130 mg/kg, a median BSAF of 0.08 was derived.

Beyer and Cromartie (1987) conducted a field study on 9 earthworm species in 27 well characterized soils with chromium concentrations ranging from 4.9 to 71 mg/kg. Based on chromium concentrations in soil and earthworms, a median BSAF of <1 was derived for all sites. Median BSAF values were < 1 for eight out of nine species. However, a median BSAF of 2.6 was reported for one species (Eisenoides lonnbergi) on one of the investigated sites close to galvanized towers.

In an additional study by Hartenstein et al. (1980), however with significant methodological shortcomings, Eisenia fetida were grown for up to four weeks in freshly activated sludge containing approx. 100 mg Cr/kg. Significant changes in tissue concentrations of Eisenia fetida were not observed and BSAF values did not exceed unity.

Regarding the bioaccumulation of chromium(III) in terrestrial plants, data from three non-reliable studies using soluble chromium (III) salts are available. Chromium uptake in bean (Phaseolus vulgaris) and wheat (Triticum aestivum) was investigated by Huffman and Allaway (1973) using chromium-51-labelled Cr(III) and Cr(VI) substances. Chromium was strongly bound to the roots of wheat and beans (> 91.5% of total Cr applied was found on roots) and translocation to aboveground tissues was low (< 7% in bean leaves, <1.5% in wheat leaves). The results are however not considered relevant for chromium uptake in soil it was studied in a hydroponic system.

Su et al. (2005) observed that 0.1 to 0.15 % of the total chromium applied was extracted by Pteris vittata based on plants grown in soils treated with up to 1000 mg Cr(III)/kg soil. Accordingly, Han et al. (2004) reported BAFs for plants ranging from 0.006 to 0.803 for chromium treatments ranging from 100 to 2000 mg Cr(III)/kg soil. The studies by Su et al. (2005) and Han et al. (2004) are however not considered reliable due to several methodological shortcomings and insufficient documentation.

According to CICAD 76 Inorganic Chromium (III) Compounds (WHO, 2009 and references therein), “although higher concentrations of chromium have been reported in plants growing in high chromium-containing soils (e.g. soil near ore deposits or chromium-emitting industries and soil fertilized by sewage sludge) compared with plants growing in normal soils, most of the increased uptake in plants is retained in roots, and only a small fraction is translocated to the aboveground part of edible plants (Cary, 1982; IPCS, 1988)…Therefore, bioaccumulation of chromium from soil to above-ground parts of plants is unlikely (Petruzzelli et al., 1987).”

Regarding the accumulation of chromium in the food chain, Huffman and Allaway (1973) investigated the fate of radiolabelled chromium in rats by feeding experiments with plants grown in chromium-containing hydroponic solution. The study is, however, poorly documented and considered not reliable. After 48h, <0.5% of the total applied chromium remained in rats and >95% of the initial chromium was found in fecal samples, pointing to a low potential for trophic magnification.

Therefore, based on a weight of evidence approach using studies on terrestrial bioaccumulation in earthworm and plant species including field data, the terrestrial bioaccumulation of chromium(III) is considered to be negligible.

Further, “chromium(III) is required by only some microorganisms for specific metabolic processes, such as glucose metabolism and enzyme stimulation. Chromium(III), in trace amounts, has been reported to be an essential component of animal nutrition and is most notably associated with glucose and fat metabolism (WHO, 2009).” Further, “natural chromium levels, available for animals living in a specific environment, depend on the natural geological and physico-chemical characteristics of the water, sediments and soils. To ensure appropriate chromium tissue levels without causing toxicity from chromium excess, it is expected that internal chromium levels are homeostatically regulated by all living organisms. Homeostatic regulation of chromium allows organisms, within certain limits, to maintain the physiologically required levels of chromium in their various tissues, both at low and high chromium intakes (Voluntary Risk Assessment of Metallic Chromium and Trivalent Chromium Compounds by ICDA, 2008 and references therein).