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Diss Factsheets

Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vitro
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented study report on chromium carbide which meets common scientific principles.
Cross-reference
Reason / purpose for cross-reference:
reference to same study
Reference
Endpoint:
basic toxicokinetics in vitro / ex vivo
Remarks:
transformation/dissolution in artificial physiological media
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented study reports which meet basic scientific principles
Reason / purpose for cross-reference:
reference to same study
Objective of study:
other: bioaccessibility / bioavailability
Qualifier:
no guideline followed
Principles of method if other than guideline:
There is not an internationally agreed guideline for these tests (e.g. OECD). However, similar tests have been conducted for several metal compounds incl. steels in previous EU risk assessments. In vitro studies on the release of metals from chromium carbide and Cr metal particles were carried out in various artificial body fluids. The results were compared with those obtained in experiments with Cr(III) oxide.

Jiang et al. (2012): The aim of these tests is to assess the dissolution of chemical compounds in a set of artificial physiological media. The test media are selected to simulate relevant human-chemical interactions (as far as practical), i.e. contact of a test substance with skin, a substance entering the human body by inhalation or by ingestion into the gastro-intestinal tract. Principle of test is similar to OECD Series on testing and assessment number 29 guidance document on transformation/dissolution of metals and metal compounds in aqueous media (2001; document ENV/JM/MONO(2001)9). The dissolved amount of the test item was specified by measured dissolved Cr concentrations in the test media under the applied test conditions.
GLP compliance:
not specified
Specific details on test material used for the study:
Jiang et al. (2012):
Powders of "reaction mass of heptachromium tricarbide and trichromium dicarbide" particles (Cr-C, sized less than 40 µm, surface area of 1.26 m2/g BET) were supplied by Delachaux,France. The test item referred to as Cr-C in the published research article " Chemical Stability of Chromium Carbide and Chromium Nitride powders compared with chromium metal in synthetic biological solutions" by Jiang et al. (ISRN Corrosion 2012, doi:10.5402/2012/379697), is a multiconstituent substance: reaction mass of heptachromium tricarbide CAS# 12075-40-0 and trichromium dicarbide CAS# 12012-35-0 (see attached).
Radiolabelling:
no
Species:
other: in vitro (simulated human body fluids) (Jiang et al., 2012)
Duration and frequency of treatment / exposure:
Jiang et al. (2012): Samples were taken after 2, 4, 8, 24 and 168 h.
Dose / conc.:
100 other: mg of test item/L artificial media
Details on study design:
Particles of the test compounds were immersed in artificial body fluids (artificial sweat pH 6.5, phosphate buffered saline pH 7.2, Gamble's solution pH 7.4, artificial lysosomal fluid pH 4.5 and artificial gastric fluid pH 1.7). The exposures were carried out for up to 168 h after which the released metals were detected.
In addition, the surface composition of the particles was measured before and after the exposures.
The experiments were carried out in 30C and/or 37C.
Preliminary studies:
The results showed that the release of chromium from chromium carbide was very low. In the worst-case situation (artificial gastric fluid pH 1.5) the amount of Cr released after 168 h was <0.00005 µg/µg Cr in the loaded particles (<0.005%). In the various test solutions, Cr release from chromium carbide was comparable to or lower than the release from pure Cr metal or chromium(III) oxide. The release rate increased with decreasing pH of the test media. The differences in the release rates of the tested powders were not attributable to the differences in surface area or to the particle size distribution in solution. The surface area of the tested chromium carbide powder was 1.26 m2/g, whereas the corresponding area for the chromium metal particles was 0.46 m2/g.
Type:
other: bioaccessibility
Results:
Released amount of chromium expressed as % (µg Cr/µg Cr*100) for Cr-C: GST (<0.005%) > ALF (<0.004%) > ASW (<0.003%) > PBS (<0.001%) = approx. GMB (<0.001%)
Bioaccessibility (or Bioavailability) testing results:
see below

Mean released concentrations and standard deviations (SD) in µg/L of chromium for Cr-C particles after exposure in the different biological fluids (GST-gastric fluid, ALF - artificial lysosomal fluid, ASW - artificial sweat, GMB - Gamble's solution, PBS - phosphate buffered saline). Values corrected for Cr background.

GST

ALF

ASW

PBS

GMB

h

Mean

SD

Mean

SD

Mean

SD

Mean

SD

Mean

SD

2

1.09

0.27

1.23

0.44

1.50

0.62

1.41

0.50

0.31

0.46

4

1.60

0.54

0.90

0.07

1.29

0.86

0.82

0.53

0.47

0.10

8

0.92

0.14

1.31

0.43

0.77

0.78

0.62

0.27

0.31

0.14

24

1.43

0.22

1.80

0.12

1.16

0.29

2.03

0.41

0.71

0.62

168

4.73

0.56

3.92

0.19

2.82

0.59

0.56

0.068

0.80

0.47

Measured dissolved Cr concentrations in method blanks:

h

GST pH 1.7

ALF pH 4.5

ASW pH 6.5

PBS pH 7.2

GMB pH 7.4

2

0.66

2.30

1.39

0.91

0.58

4

0.26

2.26

1.40

0.70

0.21

8

0.72

2.29

1.75

0.90

0.51

24

0.59

2.23

1.37

0.81

0.17

168

0.17

2.43

1.76

0.58

0.25

Conclusions:
The release studies showed that very small amounts of metals are released from chromium carbide ("reaction mass of heptachromium tricarbide and trichromium dicarbide", Jiang et al. 2012), Cr metal and Cr2O3 into different artificial body fluids. Released chromium expressed as % (µg Cr/µg Cr*100) are below 0.005% for chromium carbide ("reaction mass of heptachromium tricarbide and trichromium dicarbide", Jiang et al. 2012) in all investigated artificial fluids.
Executive summary:

In vitro studies on the release of chromium from chromium carbide particles were carried out in various artificial body fluids. The results were compared with those obtained in experiments with pure Cr metal or chromium(III) oxide.

The results showed that the release of chromium from chromium carbide was very low (<0.005% of the total chromium amount), being at a similar level as from chromium metal or chromium(III) oxide. The release rate increased with decreasing pH of the test media and it was not related to the surface area of the particles.

As extremely small amounts of chromium is released from chromium carbide, Cr metal and Cr2O3, the bioaccessibility is very low. This leads to a situation with very low bioavailability.

Data source

Reference
Reference Type:
publication
Title:
Chemical stability of chromium carbide and chromium nitride powders compared with chromium metal in synthetic biological solutions
Author:
Jiang, T., Odnevall Wallinder, I., G. Herting
Year:
2012
Bibliographic source:
ISRN Corrosion, doi:10.5402/2012/379697

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
other: EN 1811
Deviations:
yes
Remarks:
in addition to artificial sweat, other artificial body fluids were also used as tets medium
Principles of method if other than guideline:
Release of chromium from chromium carbide was tested. For sensitisation, the amount of metals released into artificial sweat is highly relevant.
GLP compliance:
no
Type of study:
other: EN 1811

Test material

Constituent 1
Reference substance name:
Reaction mass of heptachromium tricarbide and trichromium dicarbide
EC Number:
915-035-5
Molecular formula:
Cr7C3; Cr3C2
IUPAC Name:
Reaction mass of heptachromium tricarbide and trichromium dicarbide
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Details on test material:
Chromium carbide: Cr balance, Fe 0.077%, C 10.1%, N 0.07%, Si 0.021%, Al 0.015%, O 0.075%. In the text the chromium carbide was referred to as Cr7C3. Supplier Delachaux. Particle size <40 µm. In the characterization studies done in the paper, the predominating crystalline phase was identified as Cr7C3. Cr2O3 was also identified.
In an attached paper, the distributor of the test material confirmed it as a reaction mass of heptachromium tricarbide and trichromium dicarbide.

Results and discussion

In vitro / in chemico

Results
Remarks on result:
other: see "remarks"
Remarks:
The release of chromium from the tested chromium carbide powder into artificial sweat solution was very low: < 0.003% of the chromium contents of the powder were detected in the test solution after 168 hours. The release was similar as for chromium metal. The paper did not present any data on the presence of Cr(VI).

Any other information on results incl. tables

The release of chromium from the tested chromium carbide powder into artificial sweat solution was very low: < 0.003% of the chromium contents of the powder were detected in the test solution after 168 hours. The release was similar as for chromium metal. The paper did not present any data on the presence of Cr(VI).

Applicant's summary and conclusion

Conclusions:
The release of chromium from chromium carbide into artificial sweat was very low, and therefore it can be concluded that the potential for chromium carbide to cause sensitisation due to dissolved metal is highly unlikely.