Chromium trioxide

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1983 to 1985

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The EU RAR summarises the results of two studies which have limitations regarding study design and reliability. However, the results of these studies, on four species, combined with data on algae, provide an adequate assessment of toxicity to primary producers in the aquatic compartment.

Qualifier:

no guideline followed

Guideline:

other: different studies included

Principles of method if other than guideline:

Two studies on four species, collectively, provide an adequate assessment of toxicity to aquatic plants.

GLP compliance:

no

Analytical monitoring:

yes

Details on sampling:

Range of methods used

Vehicle:

no

Details on test solutions:

Range of media used

Test organisms (species):

other: Lemna gibba, Lemna minor, Spirodela polyrhiza and Spirodela punctata

Test type:

other: Different test designs

Water media type:

freshwater

Limit test:

no

Remarks on exposure duration:

Range used

Post exposure observation period:

Not indicated

Hardness:

Range from different tests

Test temperature:

Range from different tests

pH:

Range from different tests

Dissolved oxygen:

Range from different tests

Salinity:

Range from different tests

Nominal and measured concentrations:

Range from different tests

Details on test conditions:

Range from different tests

Reference substance (positive control):

no

The results of the studies evaluated in the EU RAR are summarised below:

Species	Endpoint: growth (g) biomass (b)	Value (mg/L)	Reference
Lemna gibba	8 d NOEC (g)	0.1b,d	Staves and Knaus (1985)
Lemna minor	7 d NOEC (g)	0.11	Sloof and Canton (1983)
Spirodela polyrhiza	8 d NOEC (g)	0.1b,d	Staves and Knaus (1985)
Spirodela punctata	8 d NOEC (g)	0.5a,b,d	Staves and Knaus (1985)

a NOEC calculated as LOEC/2 from paper, effect of 14%; (b) - biomass; (g) – growth

b sodium chromate tested; all others used potassium dichromate. All concentrations as Cr.

d study rated as IIIb

Validity criteria fulfilled:

yes

Conclusions:

Based on a review of data on algae and aquatic plants, the data from the EU RAR provides an acceptable assessment of toxicity to aquatic primary producers.

Executive summary:

From two studies with four species, the 7 to 8 day NOEC values (growth) to aquatic plants range from 0.1 to 0.5 mg/L, based on tests with potassium dichromate and sodium chromate.

Where comparison is possible, the toxicity of sodium chromate or sodium dichromate, when expressed on a total chromium basis, does not appear to be significantly different from that of potassium dichromate. This is as would be expected if the equilibria between the chromate and dichromate anions are established in the test medium. Little information is available for ammonium dichromate and chromic acid, but it would be expected that their toxicity would be similar to that of the other chromates/dichromates, when expressed on a total chromium concentration basis.

Reference 2

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not specified

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

Deviations:

yes

Remarks:

no details on test concentration preparation or assessment of endpoint parameters

GLP compliance:

not specified

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: not specified
- Test concentration separation factor: sqrt(10), approx. 3.2

Test organisms (species):

Lemna minor

Details on test organisms:

TEST ORGANISM
- Common name: duckweed
- Strain: M19
- Source (laboratory, culture collection): standardized laboratory culture
- Method of cultivation: The composition of the standard medium for culturing and testing is presented in section "Any other information on materials and methods incl. tables".

ACCLIMATION
- Culturing media and conditions (same as test or not): The same standard medium was used for culturing and testing. The composition is presented in section "Any other information on materials and methods incl. tables".

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Test temperature:

25+/-1°C

Details on test conditions:

TEST SYSTEM
- Material, size, headspace, fill volume: 0.2 L test volume per concentration
- No. of colonies per vessel: 2
- No. of fronds per colony: 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The composition of the standard medium for testing is presented in section "Any other information on materials and methods incl tables".

OTHER TEST CONDITIONS
- Light intensity and quality: 35 W/m²

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
As effect parameter the specific growth rate was measured for each test group.

Key result

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

0.32 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Reported statistics and error estimates:

The NOEC value is based on nominal test concentrations.

Validity criteria fulfilled:

not applicable

Conclusions:

A toxicity study was conducted with the freshwater aquatic plant Lemna minor exposed to potassium dichromate for a test duration of 7 days under static laboratory conditions. The test conditions are well described and comparable to OECD TG 221. Hence, the results can be considered as reliable for the assessment of the toxicity of the registered substance to aquatic plants other than algae.
The test was set up with 2 colonies of 2 fronts per 0.2 mL test volume for each test vessel of the test groups. The effect parameter measured throughout the test was the specific growth rate of the test organisms in comparison to the control. Based on the obtained results, a 7-d NOEC of nominal 0.32 mg/L was determined for Lemna minor.

Executive summary:

The relative susceptibility of 11 taxonomically different species (bacteria, algae, plants, crustaceans, insects, hydrozoans, molluscs, fish and amphibians) to chemicals was determined by comparing the (semi)chronic toxicity data of 8 test substances, one of them being potassium dichromate. The test was carried out with Lemna minor representing an aquatic plant other than algae in a way that is comparable to OECD TG 221 for a test duration of 7 days under static conditions.The test was set up with 2 colonies of 2 fronts per 0.2 mL test volume for each test vessel of the test groups. The effect parameter measured throughout the test was the specific growth rate of the test organisms in comparison to the control. Based on the obtained results, a 7-d NOEC of nominal 0.32 mg/L was determined for Lemna minor.

Description of key information

1) Key_ Toxicity to aquatic plants by summary of data from European Union Risk Assessment Report: chromium trioxide, sodium chromate, sodium dichromate, ammonium dichromate and potassium dichromate

3rd. Priority List; Volume 53: NOEC = 0.1 - 0.5 mg/L (nominal) for four species from various studies with similar test durations ranging from 7 to 8 days, for potassium dichromate and sodium chromate.

2) Key_Toxicity to aquatic plants: NOEC (7d) = 0.32 mg/L for growth of Lemna minor exposed to potassium dichromate (static, freshwater, test design comparable with OECD 221)

Key value for chemical safety assessment

EC10 or NOEC for freshwater plants:

0.1 mg/L

Additional information

1) From two studies with four species, the 7 to 8 day NOEC values (growth) to aquatic plants range from 0.1 to 0.5 mg/L, based on tests with potassium dichromate and sodium chromate.

Where comparison is possible, the toxicity of sodium chromate or sodium dichromate, when expressed on a total chromium basis, does not appear to be significantly different from that of potassium dichromate. This is as would be expected if the equilibria between the chromate and dichromate anions are established in the test medium. Little information is available for ammonium dichromate and chromic acid, but it would be expected that their toxicity would be similar to that of the other chromates/dichromates, when expressed on a total chromium concentration basis.

2) The relative susceptibility of 11 taxonomically different species (bacteria, algae, plants, crustaceans, insects, hydrozoans, molluscs, fish and amphibians) to chemicals was determined by comparing the (semi)chronic toxicity data of 8 test substances, one of them being potassium dichromate. The test was carried out with Lemna minor representing an aquatic plant other than algae in a way that is comparable to OECD TG 221 for a test duration of 7 days under static conditions.The test was set up with 2 colonies of 2 fronts per 0.2 mL test volume for each test vessel of the test groups. The effect parameter measured throughout the test was the specific growth rate of the test organisms in comparison to the control. Based on the obtained results, a 7-d NOEC of nominal 0.32 mg/L was determined for Lemna minor.