Chromium trifluoride

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Type of information:

experimental study

Adequacy of study:

key study

Study period:

5 hours

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

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:

no guideline followed

Principles of method if other than guideline:

Bucillus cereus was cultured in a nutrient broth which supplemented with Fe+2, Fe+3, Cr+3, Cd+2 separately, or in combination with each other, at 37° C for 5 hours. Bacterial growth was measured every half – hour, using spectrophotometer.

GLP compliance:

no

Specific details on test material used for the study:

Cr+3 as Cr Cl3 6H20

Vehicle:

no

Details on test solutions:

Cr+3: 533 mg of CrCl 3, 6H2O were dissolved in 50 ml distilled water and then made to 100 ml to prepare 20 mM/L of chromium chloride

Test organisms (species):

Bacillus sp.

Details on inoculum:

Nutrient agar (N.A.) and nutrient broth (N.B.) (Merk) were prepared as manufacturer recommendation.Bacillus cereus ATCC (American Type Culture Collection) 11778, NCTC (National Collection of Type Culture) 1032 was used and cultivated on N.A. using streak plate method. The plate was incubated for 24 hours at 37ºC and then stored in the fridge.

Test type:

other: Agar plate

Water media type:

freshwater

Total exposure duration:

5 h

Test temperature:

37 C

Nominal and measured concentrations:

1, 5 and 10 ml of chromium stock solution was added to 199, 195 and 190 ml of Nutrient Broth and mixed well in order to have 0.1, 0.5 and 1mM concentrations of these elements.

Key result

Duration:

5 h

Dose descriptor:

EC50

Effect conc.:

ca. 50 mg/L

Nominal / measured:

nominal

Conc. based on:

other: Cr (OH)3

Basis for effect:

growth inhibition

Duration:

5 h

Dose descriptor:

EC50

Effect conc.:

ca. 25 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Remarks:

Cr3+

Basis for effect:

growth inhibition

Duration:

5 h

Dose descriptor:

EC50

Effect conc.:

ca. 55 mg/L

Nominal / measured:

nominal

Conc. based on:

other: CrF3

Basis for effect:

growth inhibition

Details on results:

Although the figures cited are entered as 'EC50', inhibition was ca 2% at the concentrations indicated. A precise EC50 was not determined.

These finding revealed that Cr3+ has partial inhibitory effects on the growth of bacteria. Bacterial growth was reduced to 79% and 76.7% using 0.1 mM/L (5.2 mg/l) and 0.5 mM/L (26 mg/l) concentration of chromium, respectively

This equates to inhibition of ca 25% at ca 96.5 mg/l Ca (OH)(NO3)2

Validity criteria fulfilled:

not specified

Conclusions:

These finding revealed that Cr3+ has partial inhibitory effects on the growth of bacteria. Bacterial growth was reduced to 79% and 76.7% using 0.1 mM/L (5.2 mg/l) and 0.5 mM/L (26 mg/l) concentration of chromium, respectively

Executive summary:

This scientifically valid study shows limited inhibition of bactial growth at approximatley 55 mg/l CrF3

Description of key information

Scientifically valid study shows limited inhibition of bactial growth at approximatley 50 mg/l equivalent of the hydroxide or chloride, with inhibition of specific bacterial strains starting at concentrations > 5 mg/l Cr III.

However, enhancement of growth at lower concentrations (essential element)

Key value for chemical safety assessment

EC50 for microorganisms:

50 mg/L

Additional information

Testing performed on other Cr III salts.