Sodium dichromate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: See "Remarks"

Remarks:

Insufficient information for assessment (validity criteria etc.), no chemical verification of exposure concentrations in test medium

Qualifier:

equivalent or similar to guideline

Guideline:

other:

Version / remarks:

USEPA bottle test method (EPA-600/9-78-018)

Deviations:

yes

Remarks:

not specified

Principles of method if other than guideline:

Green algae Selenastrum capricornutum were exposed to potassium dichromate (K2Cr2O7) in a 72-h algae growth inhibition test.

GLP compliance:

not specified

Remarks:

not specified in publication

Specific details on test material used for the study:

K2Cr2O7 (CAS 7778-50-9)

Analytical monitoring:

not specified

Details on sampling:

No information given.

Vehicle:

no

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

- Strain: no data
- Source (laboratory, culture collection): no data
- Age of inoculum (at test initiation): no data
- Inoculum cell density: 1000 cells/mL, i.e. 0.014 mg dwt/L
- Method of cultivation: flask experiment

ACCLIMATION
- no data

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

24-26 °C

pH:

8.1

Nominal and measured concentrations:

Nominal range: approx. 0.01 mg - 10 mg Cr/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 125 mL Erlenmeyer flask, closed, fill volume 50 mL
- Initial cells density: 1000 cells/mL

GROWTH MEDIUM
- Standard medium used: no
- phosphate-limited standard growth medium according to ISO/TC 147/SC 5/WG5, not further specified

OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: 8.1
- Photoperiod: continuous fluorescent light
- Light intensity and quality: 6.9 klx

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations/growht rate: counting chamber, total algal cell volume
- Biomass measurements were carried out with a Model ZBI coulter counter

TEST CONCENTRATIONS
- no detailed information on test concentrations given

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

>= 0.233 - <= 0.235 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr

Basis for effect:

growth rate

Remarks:

growth rate based on total algal cell volume

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

>= 0.01 - <= 0.012 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr

Basis for effect:

growth rate

Remarks:

growth rate based on total algal cell volume

Details on results:

- Results are given as a range, based on Weibull, probit and logit analysis

Results with reference substance (positive control):

not specified

Validity criteria fulfilled:

not specified

Remarks:

No information given

Conclusions:

In a 72-h growth inhibition test similar to the USEPA bottle test method (EPA-600/9-78-018) performed with the freshwater green algae Pseudokirchneriella subcapitata (prev. Selenastrum capricornutum), the lowest 72-h ErC10 and ErC50 values for potassium dichromate were determined with 0.66 mg/L and 0.0268 mg/L, respectively. Corresponding 72-h ErC10 and ErC50 values for chromium amount to 0.009 mg Cr/L and 0.012 mg Cr/L, respectively.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: See 'Remarks'

Remarks:

Insufficient information for assessment (validity criteria etc.), no information on control (growth); not clear how growth rate was calculated/defined

Qualifier:

no guideline followed

Principles of method if other than guideline:

Green algae Chlorella vulgaris were exposed to potassium dichromate (K2Cr2O7) in a 96-h algae growth inhibition test under static or pseudo dynamic conditions.

GLP compliance:

not specified

Remarks:

not specified in publication

Analytical monitoring:

yes

Details on sampling:

- Samples were taken after 21, 32,76 and 96 h exposure from the supernatant of each algal suspension

Vehicle:

no

Test organisms (species):

Chlorella vulgaris

Details on test organisms:

TEST ORGANISM
- Strain: 211/11b
- Source (laboratory, culture collection): Algae and Protozoa Center of Cambridge
- Age of inoculum (at test initiation): 7 days
- Method of cultivation: Axenic cultures were grown in 500-ml Erlenmeyers fixed on a gyratory shaker at 150 rpm, under 1500 ± 100 lx, a 16/8h photoperiod and at 20±1°C. Weekly subcultures were achieved by diluting a 7-day culture that contained approximately 30x10E6 cells/mL with fresh medium (10% v/v).

ACCLIMATION
- Culturing media and conditions: same as test

Test type:

other: static or pseudo-dynamic

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

20±1°C

Nominal and measured concentrations:

Nominal: 0.1, 0.2, 0.4, 0.6, 0.8 and 0.9 mg Cr/l.

Details on test conditions:

TEST SYSTEM
- Test vessel: glass test tubes (18/180 mm) for static test; glass test tubes (24x220 mm) for pseudo-dynamic test
- Fill volume: 10 mL
- Renewal rate of test solution: five times per day with an automatic pipet (only for pseudo-dynamic test)
- Initial cells density: 1.5-3.0×10E6 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: no
- Detailed composition if non-standard medium was used: Lefevre-Czarda medium supplemented with trace elements

OTHER TEST CONDITIONS
- Sterile test conditions: not specified
- Photoperiod: 16:8 h light:dark
- Light intensity and quality: 2200 ± 50 lux

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: cell counting
- Other: optical density; biomass (dry weight)

TEST CONCENTRATIONS
- Spacing factor for test concentrations: <= 2

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.47 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr

Basis for effect:

growth rate

Remarks on result:

other: static test conditions

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.12 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr

Basis for effect:

growth rate

Remarks on result:

other: pseudo-dynamic test conditions

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

0.59 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr

Basis for effect:

growth rate

Remarks on result:

other: static test conditions

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

0.16 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

growth rate

Remarks on result:

other: pseudo-dynamic test conditions

Details on results:

- The concentrations of total Cr(VI) in the water phase were between 64 and 88% of the nominal concentrations.

Validity criteria fulfilled:

not specified

Remarks:

insufficient information

Conclusions:

Green algae Chlorella vulgaris were exposed to potassium dichromate (K2Cr2O7) in a 96-h algae growth inhibition test under static or pseudo dynamic conditions. Since static conditions are conform with current guidelines (e.g. OECD 201), results are considered more reliable and comparable than reslults from non-standard testing (pseudo-dynamic). A 72 h EC50 of 0.47 mg Cr/L (nominal) was determined for the growth inhibition of chromium to C. vulgaris.

Reference 3

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: See 'Remarks'

Remarks:

No chemical verification of exposure concentrations in test medium and no information on test medium is reported. No statistical analysis was performed, therefore no reliable NOEC can be derived. Endpoint isbased on biomass, growth rate was not calculated.Rresults for wild type strain Chlorella WR1 are considered not relevant, since organisms were pre-adapted to chromium contaminations.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Toxicity to freshwater algae ChIorella pyrenoidosa was examined in a 96-h static toxicity test under continuous lighting or with a 16:8 h light:dark photoperiod.

GLP compliance:

not specified

Remarks:

not specified in publication

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Controls: Negative control

Test organisms (species):

Chlorella pyrenoidosa

Details on test organisms:

TEST ORGANISM
- Strain: 211-8b
- Source: Collection of Algae, Göttingen
- Method of cultivation: In liquid cultures under sterile autotrophic conditions
- Environmental conditions: 16:8 h light/dark cycle, 5000 lux, 1.5% CO2, 25°C

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

25°C

Nominal and measured concentrations:

0.1, 0.5, 1.0 and 2.0 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
- Initial cells density: 5x10E5 or 0.5x10E5 cells/mL
- Control end cells density: 2.3x10E7 (continuous light), 0.54x10E7 (16:8 h light/dark)

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: Continuous light or 16:8 h light/dark
- Light intensity and quality: 5000 lux

EFFECT PARAMETERS MEASURED: Total dry weight, cell number and total chlorophyll
- Determination of cell concentrations: Determined by hemocytometer counting in a Zeiss-Standard microscope.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2 and 5
- Test concentrations: 0.1, 0.5, 1.0 and 2.0 mg/L (nominal)

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

0.1 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr

Basis for effect:

biomass

Remarks:

dry weight

Duration:

96 h

Dose descriptor:

LOEC

Effect conc.:

0.5 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr

Basis for effect:

biomass

Remarks:

dry weight

Details on results:

- Control end cells density: 2.3x10E7 (continuous light), 0.54x10E7 (16:8 h light/dark)

Reported statistics and error estimates:

No statistical analysis performed.

Table 1: Dry weight, chlorophyll content and cell numbers of C. pyrenoidosa after 96 h

Cr concentration [mg/L]	Total dry weight [g/L]		Total chlorophyll [% of dry weight]		Cell number x 10E7
	continuous light	16:8 h	continuous light	16:8 h	continuous light	16:8 h
control	2.45	0.83	3.0	3.2	2.30	0.54
0.1	2.49	0.94	2.4	3.3	2.34	0.50
0.5	2.11	0.66	1.6	1.7	3.83	0.46
1.0	1.88	0.29	1.4	1.6	4.10	0.37
2.0	1.41	0.08	1.2	1.6	4.70	0.36

Validity criteria fulfilled:

not specified

Remarks:

growth rates were not calculated

Conclusions:

The potential toxicity of hexavalent chromium (potassium dichromate, K2CrO7) to the freshwater algae ChIorella pyrenoidosa was tested in a 96 h static toxicity test under continuous lighting or with a 16:8 h light:dark photoperiod. Based on biomass (dry weight), inhibiting effects were observed at 0.5 mg Cr/L (LOEC) and the corresponding NOEC was determined at 0.1 mg Cr/L (nominal, biomass).

Reference 4

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: See 'Remarks'

Remarks:

no chemical verification of exposure concentrations in test medium, otherwise only minor deviations from guideline

Qualifier:

according to guideline

Guideline:

other: EPA-600/9-78-018 (The Selenastrum Capricornutum Printz Algal Assay Bottle Test)

Version / remarks:

1978

GLP compliance:

not specified

Remarks:

not specified in publication

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Controls: Negative control

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

24 mg/L

Test temperature:

25±1°C

pH:

8.0

Nominal and measured concentrations:

Test concentrations not specified (6-8 concentrations tested).

Details on test conditions:

TEST SYSTEM
- Test vessel: 125 mL glass Erlenmeyer flask
- Volume: 50 mL
- Agitation: 130 rpm
- Initial cells density: 0.28 mg dry wt./L (1.00 x 10E4 cells/mL) or 0.024 mg dry wt./L (1.00 x 10E3 cells/mL)
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): >= 5

GROWTH MEDIUM
- Standard medium used: Yes, ISO standard medium modified to contain 1/20 of original phosphate (18 µg P/L)
- Medium characteristics: 50 mg/L NaHCO3, 100 µg/L Na2EDTAx2H2O

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Water obtained from Millipore Super Q system

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: Continuous fluorescent light (Daylight)
- Light intensity and quality: 4000 lux (~60µE/[m2 x s])

EFFECT PARAMETERS MEASURED: Growth
- Determination of cell concentrations: Biomass measurements with a model ZBI Coulter Counter equipped with a mean cell volume calculator (MCV) and 100 µm aperture tube once a day. Dry weights (70°C) were calculated from cell volumes by using a conversion factor of 5.0 x 10E-7 (mg dry wt./L) /[MCV (µE3) x cells / mL].

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.11 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.99 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr

Basis for effect:

growth rate

Details on results:

- 72 h average growth rate in control cultures: 1.75 /day

Results with reference substance (positive control):

3,5-Dichlorophenol:
EC10: 1.9 mg/L (growth rate), EC50: 6.3 mg/L (growth rate)

Reported statistics and error estimates:

Dose-response curves were obtained by nonlinear least squares fit model.

Validity criteria fulfilled:

yes

Remarks:

control growth rate 1.75/day; section-by-section growth rate and CV of control replicates not assessable (raw data not given)

Conclusions:

In a 72-h growth inhibition test performed according to US EPA-600/9-78-018 with freshwater algae P.subcapitata, a 72 h EC10 and EC50 of 0.11 and 0.99 mg Cr/L (nominal), respectively, were determined based on algal growth rate.

Reference 5

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: See 'Remarks'

Remarks:

No analytic verification of Cr(VI) exposure concentrations in test medium. The exposure duration is not defined. Data on growth rate in the control is not shown.

Qualifier:

no guideline followed

Principles of method if other than guideline:

The toxicity of potassium dichromate to the marine diatom Thalassiosira pseudonana was investigated in artificial ocean water with variable sulfate concentrations and fixed salinities of 0.32 and 3.2 ppt. The 50% inhibition of the algal growth rate (EC50) was determined via in vivo fluorescence measurement.

GLP compliance:

not specified

Remarks:

not specified in publication

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Dissolved in distilled deionized water

Test organisms (species):

other: Thalassiosira pseudonana

Details on test organisms:

TEST ORGANISM
- Strain: Clone 3H
- Source (laboratory, culture collection): Collection R. R. L. Guillard at Woods Hole Oceanographic Institution
- Method of cultivation: Same as test

ACCLIMATION
- Acclimation period: Test were started via inoculation of 0.1 mL of a rapidly grown algal pre-culture in SOW-WC medium at the experimental salinity.
- Culturing media and conditions: Same as test

Test type:

static

Water media type:

brackish water

Limit test:

no

Remarks on exposure duration:

Not specified

Hardness:

Not reported

Test temperature:

20 ± 1°C

pH:

At the start ~8.5; During rapid growth phase ~9.5

Dissolved oxygen:

Not reported

Salinity:

0.32 and 3.2 ‰

Conductivity:

Not reported

Nominal and measured concentrations:

Nominal:
At salinity of 0.32 ppt: 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1 μM Cr (0.00052, 0.0010, 0.0026, 0.0052, 0.010, 0.026, 0.052 mg Cr/L)
At salinity of 3.2 ppt: 0.1, 0.2, 0.5, 1, 2, 5, 10 μM Cr (0.0052, 0.010, 0.026, 0.052, 0.104, 0.26 and 0.52 mg Cr/l)

Details on test conditions:

TEST SYSTEM
- Test vessel: Pyrex test tubes
- Material, size, headspace, fill volume: Autoclaved, acid-washed Siliclad coated 50 mL Pyrex test tubes.
- Test volume: 30 mL
- Initial cells density: 2 x 10^4 cells (salinity of 3.2 ppt); 6 x 10^4 cells (salinity of 0.32 ppt)

GROWTH MEDIUM
- Standard medium used: no, artificial estuarine water made up by diluting Standard Ocean Water (SOW) with the major salts of the nutrient enriched artificial freshwater medium WC.
- Detailed composition if non-standard medium was used: The medium was autoclaved prior to addition of trace metals, Fe-EDTA and vitamins at f/2 levels. SOW-WC with variable sulfate and fixed salinity were made by substitution of sulfate by chloride salts in the stock solutions and mixing of the corresponding stocks.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Standard Ocean Water (SOW)
- Culture medium different from test medium: no

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: 16:8 h light:dark
- Light intensity and quality: Cool-white fluorescent light at 170 µE x m^-2 x s^-1
- Salinity (for marine algae): 3.2 and 0.32 ppt (ng/L)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable):
- Determination of cell concentrations: Cell growth was determined daily by vivo fluorescence using a fluorometer

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2 and 2.5

Reference substance (positive control):

no

Key result

Dose descriptor:

EC50

Effect conc.:

0.341 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr

Basis for effect:

growth rate

Remarks on result:

other: Salinity: 3.2 ppt; Sulphate: 2.9 mM

Details on results:

- The control growth rate was much lower in the 0.32‰ experiments (~0.7 day-1) than in the 3.2‰ experiments (~2 day-1), therefore test conditions at 3.2 ‰ were considered more appropriate for the tested species. The "normal" sulphate concentration at 3.2‰ would be around 2.9 mM (EU RAR 2005). Thus, the EC50 derived at a salinity of 3.2 ‰ and a sulphate concentration of 2.9 mM is considered most relevant.
- Toxicity effects of Cr in a sulfate concentration and salinity-dependent manner were observed.

Reported statistics and error estimates:

EC50 Growth rate and fluorescence yield were calculated by the maximum likelihood method using a FORTRAN program for iterative calculation.

Table 1.: Calculated concentrations estimated to cause 50 % inhibition of growth rate (EC50), for different sulfate concentrations and salinities (0.32 and 3.20 ppt).

Salinity (ppt)	SO4^2-(mM)	EC50 (growth rate, µM)	EC50 (growth rate, mg Cr/L)
3.20	2.90	6.56	0.341
3.20	1.45	3.80	0.198
3.20	0.58	1.44	0.075
3.20	0.29	0.66	0.034
3.20	0.15	0.40	0.021
0.32	0.38	0.75	0.039
0.32	0.19	0.23	0.012
0.32	0.08	0.19	0.010
0.32	0.04	0.10	0.005
0.32	0.02	0.04	0.002

Validity criteria fulfilled:

not specified

Remarks:

raw data on growth rate not shown

Conclusions:

The conducted study investigated the potential effects of Cr exposure on the cell growth of the unicellular green alga Thalassiosira pseudonana in artificial ocean water at variable sulfate concentrations and two salinities. The control growth rate was much lower in the 0.32‰ experiments than in the 3.2‰ experiments, therefore test conditions at 3.2 ‰ were considered more appropriate for the tested species. The "normal" sulphate concentration at 3.2‰ would be around 2.9 mM (EU RAR 2005). Thus, the EC50 of 0.341 mg Cr/L derived at a salinity of 3.2 ‰ and a sulphate concentration of 2.9 mM is considered most relevant.

Reference 6

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: See "Remarks"

Remarks:

Insufficient information for assessment (validity criteria etc.), no chemical verification of exposure concentrations in test medium

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Microcystis aeruginosa (Cyanobacteria) were exposed to potassium bichromate (K2Cr2O7) in a 96-h algae growth inhibition test under static conditions.

GLP compliance:

not specified

Remarks:

not specified in publication

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Microcystis aeruginosa

Details on test organisms:

TEST ORGANISM
- Source: standardized laboratory cultures

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

see below

Test temperature:

23±2 °C

Nominal and measured concentrations:

Test concentrations not reported

Details on test conditions:

TEST SYSTEM
- Initial cells density: 1.5*10^6 cells in 150 mL
- No. of vessels per concentration (replicates): 3

GROWTH MEDIUM
- for detailed composition, see below

OTHER TEST CONDITIONS
- Sterile test conditions: no data
- Adjustment of pH: no data
- Photoperiod: continuous light
- Light intensity and quality: 13 W/m2

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: specific growth rate

Reference substance (positive control):

not specified

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

0.35 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr

Basis for effect:

growth rate

Remarks:

specific growth rate

Details on results:

- Exponential growth in the control (for algal test): no information available

Validity criteria fulfilled:

not specified

Remarks:

insufficient data presented (no information on control growth, section-by-section growth)

Conclusions:

In a 96-h growth inhibition test performed with the freshwater cyanobacteria M. aeruginosa, a 96-h NOEC value of 1 mg/L (nominal, specific growth rate) was derived for potassium dichromate, corresponding to a 96-h NOEC of 0.35 mg chromium/L (nominal, specific growth rate).

Reference 7

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: See "Remarks"

Remarks:

Insufficient information for assessment (validity criteria etc.), no chemical verification of exposure concentrations in test medium and endpoints are based on biomass only (growth rate not calculated).

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Green algae Scenedesmus pannonicus were exposed to potassium bichromate (K2Cr2O7) in a 96-h algae growth inhibition test under static conditions.

GLP compliance:

not specified

Remarks:

not specified in publication

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Scenedesmus pannonicus

Details on test organisms:

TEST ORGANISM
- Source: standardized laboratory cultures

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

23±2 °C

Nominal and measured concentrations:

Test concentrations not reported

Details on test conditions:

TEST SYSTEM
- Initial cells density: 1.5*10^6 cells in 150 mL
- No. of vessels per concentration (replicates): 3

GROWTH MEDIUM
- for detailed composition, see below

OTHER TEST CONDITIONS
- Sterile test conditions: no data
- Adjustment of pH: no data
- Photoperiod: continuous light
- Light intensity and quality: 13 W/m2


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- growth (biomass)

Reference substance (positive control):

not specified

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

0.11 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr

Basis for effect:

biomass

Details on results:

- Exponential growth in the control (for algal test): no information available

Validity criteria fulfilled:

not specified

Remarks:

insufficient data presented (no information on control growth, section-by-section growth)

Conclusions:

In a 96-h growth inhibition test performed with the freshwater algae S. pannonicus, a 96-h NOEC value of 0.32 mg/L (nominal, biomass) was derived for potassium dichromate, corresponding to a 96-h NOEC of 0.11 mg chromium/L (nominal, biomass).

Description of key information

Reliable toxicity data (Klimisch 1 or 2) of soluble hexavalent chromium substances are lacking for algae or cyanobacteria but available studies (Klimisch 3) were applied in a weight-of-evidence approach.

Freshwater

Relevant EC50 values are reported in 3 studies for the inhibition of growth rate of freshwater algae species Chlorella vulgaris and Pseudokirchneriella subcapitata (prev. Selenastrum capricornutum), and range from 0.23 to 0.99 mg Cr/L (Christensen and Nyholm, 1984; Jouany et al., 1983; Nyholm, 1991 - all Klimisch 3).

Relevant NOEC or EC10 values for the inhibition of growth rate of freshwater algae were derived in 3 studies for one green algae species (P. subcapitata) and one cyanobacterium (Microcystis aeruginosa). Respective NOEC/EC10 values range from 0.01 to 0.35 mg Cr/L (Christensen and Nyholm, 1984; Nyholm, 1991; Sloof and Canton, 1983 - all Klimisch 3).

In addition, NOEC values of 0.1 and 0.11 mg Cr/L are available for the effect on biomass of green algae Chlorella pyrenoidosa and Scenedesmus pannonicus (Meisch and Schmitt-Beckmann, 1979; Sloof and Canton, 1983 - all Klimisch 3).

The lowest reported effect concentrations, i.e. the EC50 of 0.23 mg Cr/L and the NOEC of 0.01 mg Cr/L are applied as key values.

Saltwater

An EC50 of 0.341 mg Cr/L was derived for the inhibition of growth rate of marine diatom Thalassiosira pseudonana at a salinity of 3.2 ‰ and a sulphate concentration of 2.9 mM in an unreliable study (Riedel, 1984; Klimisch 3). NOEC or EC10 values were, however, not derived.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.23 mg/L

EC50 for marine water algae:

0.341 mg/L

EC10 or NOEC for freshwater algae:

0.01 mg/L