Potassium chromate

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

1978 to 1990

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The EU RAR summarises results from a number of algal studies which, individually, have limitations regarding study design and reliability. However, the results of these studies when taken as a whole, provide an adequate assessment of the toxicity to algae. The data are considered to fulfil the criteria laid down in Annex XI to Regulation 1907/2006: adequate for classification and labelling, adequate coverage of key parameters (growth inhibition), exposure duration comparable or longer that Article 13(3) methods (72 hours), adequate documentation provided: EU RAR, of which parts have been copied to this endpoint record. Reliability for endpoint also increased based on test results from several species.

Data source

Reference

Reference Type:

review article or handbook

Title:

European Union Risk Assessment Report: chromium trioxide, sodium chromate, sodium dichromate, ammonium dichromate and potassium dichromate

Author:

European Chemicals Bureau

Year:

2005

Bibliographic source:

3rd. Priority List; Volume 53

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Several studies, collectively, provide a weight-of-evidence to support toxicity to algae

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Chromium trioxide

EC Number:

215-607-8

EC Name:

Chromium trioxide

Cas Number:

1333-82-0

IUPAC Name:

1333-82-0

Constituent 2

Reference substance name:

Potassium dichromate

EC Number:

231-906-6

EC Name:

Potassium dichromate

Cas Number:

7778-50-9

Molecular formula:

Cr2H2O7.2K

IUPAC Name:

sodium dichromate

Constituent 3

Reference substance name:

Sodium chromate

EC Number:

231-889-5

EC Name:

Sodium chromate

Cas Number:

7775-11-3

Molecular formula:

CrH2O4.2Na

IUPAC Name:

disodium dioxido(dioxo)chromium

Details on test material:

Most of the algal toxicity data have been generated with potassium dichromate. 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.

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Various sampling procedures based on multiple studies

Test solutions

Vehicle:

no

Details on test solutions:

Various test media prepared based on multiple studies in freshwater and brackish water

Test organisms

Test organisms (species):

other: Range of species tested

Study design

Test type:

static

Limit test:

no

Remarks on exposure duration:

Range used from several studies

Post exposure observation period:

None reported

Test conditions

Hardness:

Range used from several studies

Test temperature:

Range used from several studies

pH:

Range used from several studies

Dissolved oxygen:

Not applicable

Salinity:

Range used from several studies

Nominal and measured concentrations:

Range used from several studies

Details on test conditions:

Range used from several studies

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Remarks on result:

other: See "Any other information on results incl. tables" below.

Details on results:

Potassium dichromate is recommended as a reference substance in the algal inhibition test (Method C.3; EEC, 1992). A ring test involving 16 laboratories determined the mean 72h-EC50 values for Scenedesmus subspicatus and Selenastrum capricornutum. The mean and range of the
values obtained (for the two species combined) are shown below on both a K2Cr2O7- concentration basis (EEC, 1992) and also converted to the equivalent chromium concentration.

Endpoint mean value range:
EC50(growth rate) 0.84 mg K2Cr2O7/l 0.6-1.03 mg K2Cr2O7/l =0.30 mg Cr/l =0.21-0.36 mg Cr/l
EC50(biomass) 0.53 mg K2Cr2O7/l 0.20-0.75 mg K2Cr2O7/l =0.19 mg Cr/l =0.071-0.26 mg Cr/l.

Most of the algal toxicity data have been generated with potassium dichromate. 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.

The available EC50 values for algae and plants range from 0.13 to 4.6 mg/l Cr; NOEC values are in the range 0.01 to 0.64 mg/l Cr.

With marine algae, salinity and sulphate ion concentration have been shown to be important factors in determining the toxicity of chromium (VI). The toxicity of chromium (VI) is generally highest at low salinities (<2¿) and low sulphate ion concentrations (Riedel, 1984 and 1985;Frey et al., 1983). At higher salinities, marine alga appears to be of similar or slightly lower sensitivity as freshwater algae.

Riedel (1985) studied the uptake of chromium (VI) (as potassium dichromate) by the marine diatom Thalassiosira pseudonana at low salinities (0.32-3.2¿) and sulphate ion concentrations. It was found that the rate of uptake of chromium (VI) was approximately linear with time, proportional to the aqueous chromium (VI) concentration and inversely proportional to the aqueous sulphate concentration. The concentration of chromium (VI) that inhibited cell growth also inhibited sulphate uptake.

Any other information on results incl. tables

The results of the algal toxicity studies evaluated in the EU RAR are summarised below.

Species	Endpoint: growth (g) biomass (b)	Value (mg/L)	Reference
Algae - freshwater
Chlamydomonas sp	10 d NOEC (g)c	0.5	Cairns Jr. et al. (1978)
Chlorella vulgaris	72 h IC50 (g)	0.47	Jouany et al. (1982)
Chlorella pyrenoidosa	96 h NOEC (b)	0.1	Meisch and Schmitt-Beckmann (1979)
Chlorella sp (wild)	96 h NOEC (b)	0.1	Meisch and Schmitt-Beckmann (1979)
Lyngbya (blue-green)	18 d NOEC (g)c	0.1	Cairns Jr. et al. (1978)
Microcystis aeruginosa (bluegreen)	96 h NOEC (g)	0.35	Sloof and Canton (1983)
Scenedesmus pannonicus	96 h NOEC	0.11	Sloof and Canton (1983)
Scenedesmus subspicatus	72 h EC50 (g)	4.6	Kuhn and Pattard (1990)
	72 h EC10 (g)	0.64
	72 h EC50 (b)	0.13
	72 h EC10 (b)	0.032
Selenastrum capricornutum	72 h IC50 (g)	0.99	Nyholm (1991)
	72 h IC10 (g)	0.11
	96 h EC50 (b)	0.217	Greene et al. (1988)
	72 h EC50 (g)	0.233	Christensen et al. (1983) Christensen and Nyholm (1984)
	72 h EC10 (g)	0.01
Algae- brackish water
Thalassiosira pseudonana	EC50	0.341	-l Riedel(1984)

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.

c duration of test too long for inclusion in PNEC derivation.

d study rated as IIIb

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Based on a review of existing algal data from the EU RAR, an acceptable assessment of toxicity was achieved.

Executive summary:

From the EU RAR, most of the algal toxicity data have been generated with potassium dichromate. 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.

The available EC50 values for algae range from 0.13 to 4.6 mg/l Cr; NOEC values are in the range 0.01 to 0.64 mg/l Cr. With marine algae, salinity and sulphate ion concentration have been shown to be important factors in determining the toxicity of chromium (VI). The toxicity of chromium (VI) is generally highest at low salinities (<2¿) and low sulphate ion concentrations (Riedel, 1984 and 1985; Frey et al., 1983). At higher salinities, marine alga appears to be of similar or slightly lower sensitivity as freshwater algae.