Chromium chloride, basic

Toxicity to soil microorganisms

Administrative data

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

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:

Although many publication note that Cr III is less toxic than Cr VI, this research covers the conversion of Cr VI to Cr III under microbial influence. The use of microbial innoculation is used in remdiation of Cr VI contaminiated soils and this paper considered tolerance to Cr VI.
The fact that the micro-organisms survive the Cr VI and then thrive in the Cr III enriched media demonstrates toxicity to Cr III to be significanty lower than Cr VI.

Cross-reference

Reason / purpose for cross-reference:

data waiving: supporting information

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

2017

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 850.5100 (Soil Microbial Community Toxicity Test)

Principles of method if other than guideline:

The effect of Cr on Pseudomonas aeruginosa growth was checked by comparing the growth of Pseudomonas aeruginosa in medium containing certain concentration of chromium and in medium without chromium.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

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:

Potassium dichromate

Specific details on test material used for the study:

Specific details not provided

Sampling and analysis

Analytical monitoring:

yes

Test substrate

Vehicle:

yes

Details on preparation and application of test substrate:

Water

Test organisms

Test organisms (inoculum):

soil

Study design

Total exposure duration:

24 h

Test conditions

Test temperature:

These plates were incubated at 37ºC

Moisture:

In water based media

Details on test conditions:

Nutrient agar used

Nominal and measured concentrations:

Nominal 0, 20, 50, 100, 150, 200 ppm

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

24 h

Dose descriptor:

EC100

Effect conc.:

> 50 other: ppm

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Cell growth

Effect concentrations 2

Duration:

24 h

Dose descriptor:

EC0

Effect conc.:

ca. 50 other: ppm

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Cell growth

Details on results:

Pseudomonas aeruginosa grew normally up to at least 50 ppm of Cr (VI), and was killed at 100 ppm of Cr (VI)
Biotransformation efficiency of Cr (VI) into Cr (III)

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

Although many publication note that Cr III is less toxic than Cr VI, this research covers the conversion of Cr VI to Cr III under microbial influence. The use of microbial innoculation is used in remdiation of Cr VI contaminiated soils and this paper considered tolerance to Cr VI.
The fact that the micro-organisms survive the Cr VI and then thrive in the Cr III enriched media demonstrates toxicity to Cr III to be significanty lower than Cr VI.
It was also found that Pseudomonas aeruginosa reduced Cr (VI) into Cr (III) with the conversion efficiency of 94% after and extended 48h treatment.

Executive summary:

Chromium 3+ exists in natural soils and is well tolerated by micro-organisms.