Chromium chloride, basic

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

96 hours

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Justification for type of information:

As with all inorganic salts, the significance for toxicity or environmental assessment is the presence of specific ions that will form when in solution or when in biological systems.In the case of Cr III salts, the counter ion will have an effect on solubility and this is itself dependant on the type of media being used and in particular the pH of that media. It is generally accepted that in the case of metal salts, testing with salts that are soluble in the respective test media will ensure maximum exposure of the metal ions. This will include chlorides and nitrates as being more soluble and will indeed have relevance when dissolved in acid media, such as if ingested.Read-across to other chromium III salts is therefore considered valid as long as the exposure in the test system is greater than would be expected for the substance under review for registration.

Qualifier:

according to guideline

Guideline:

other: Protocol for bioassessment of hazardous waste sites. EPA-600/2-83-05

Principles of method if other than guideline:

96 hours exposure period

GLP compliance:

no

Specific details on test material used for the study:

Chromium chloride used as a reference, but analysis and result all expressed as Cr3+

Analytical monitoring:

yes

Details on sampling:

Detaills not described

Vehicle:

no

Test organisms (species):

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

Details on test organisms:

Algal cells (10,OOO cells/ml) were exposed to the test solutions for 96 h. Algae cultured in algal assay medium served as the controls.

Test type:

static

Water media type:

freshwater

Remarks:

Natural water, contaminated with Chromium

Limit test:

no

Total exposure duration:

96 h

Remarks on exposure duration:

This exceeds normal guidelines for 72 hour exposure. This should not greatly impact on the results in since this is a satable inorganic substance.

pH:

Samples on which algal assays were performed were adjusted with 0.1 N NaOH, as necessary, to a final pH that ranged from 5.6 to 8.9

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

0.3 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

chromium

Basis for effect:

biomass

Duration:

96 h

Dose descriptor:

IC50

Effect conc.:

ca. 0.75 mg/L

Nominal / measured:

estimated

Conc. based on:

other: Registered substance

Basis for effect:

biomass

Details on results:

The research using different contaminated waters resulted in an EC50 range of 0.229 - 0.360 mg/l with a mean of 0.265 mg/l CrThese have been rounded to 0.3 mg/l Cr.

Reported statistics and error estimates:

Linear regression analysis [9] was used to calculate the mean inhibitory concentrations (EC50) related to measured chromium concentrations.The difference in yields between the control and test flasks was calculated and reported as percent inhibition.

Validity criteria fulfilled:

not specified

Conclusions:

Water from a number of contaminated sources was assessed for toxicity and a relatively consistant EC50 determined of ca 0.3 mg/l Cr
Based on Cr3+ IC50 0.3 mg/l, EC50 of hydroxy chloride is ca 0.75 mg/l

Executive summary:

Peer reviewed research using scientifically valid methods determined the inhibitory concentrations of Cr3+ to algea

Description of key information

Although under laboratory conditions chromium appears to have an impact on algal growth at concentrations sufficiently low for classification, the presence of sediments and salts found in natural water will limit the solubility of chromium 3+ in the environment in view of ion exchange quickly leading to precipitation as Cr(OH)3

Data on chloride suggests tolerance by freshwater species to be in excess of 100 mg/l Cl.

Many 'freshwater' sources have chloride > 100 mg/l.

Standard OECD hard test-water contains > 100 mg/l

Key value for chemical safety assessment

EC50 for freshwater algae:

0.75 mg/L

Additional information

Based on Cr3+ IC50 0.3 mg/l, EC50 of hydroxy chloride is ca 0.75 mg/l