Trichromium dicarbide

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

An embryonic stem cells test showing negative results confirmed the lack of embryotoxicity of Cr(III).

Effect on fertility: via oral route

Dose descriptor:

NOAEL

1 368 mg/kg bw/day

Effect on fertility: via inhalation route

Dose descriptor:

NOAEC

30 mg/m³

Additional information

No data were available on testing reproductive toxicity of trichromium dicarbide and therefore chromium(III) oxide studies were evaluated. Inhalation exposure of chromium(III) oxide did not cause any changes in ovarian or testicular weights, or in sperm motility, morphology or concentration. The NOAEC for inhalation exposure is 30 mg/m3 Cr(III), which was the highest dose tested in a 13 week inhalation study. An oral study using doses as high as 1368 mg Cr(III)/kg bw/day did not show any fertility effects. The study was not performed according to any guidelines, but the poor oral bioavailability of chromium supports these observations. The release of chromium from chromium carbide is very similar to the release from chromium(III) oxide and therefore the results obtained with these substances can readily be used in the assessment of trichromium dicarbide. The dermal route is insignificant for toxicity to reproduction caused by trichromium dicarbide, as the substance is practically insoluble and it is not expected to be absorbed from the skin to the systemic circulation.

Short description of key information:

A subchronic rat inhalation toxicity study with chromium(III) oxide did not cause any fertility effects even at the highest dose tested. The NOAEC was 44 mg Cr2O3/m3, corresponding to 30 mg Cr(III)/m3.

A 60-day study, with rats fed high doses of Cr2O3 in bread did not show any fertility effects even at the highest dose of 1368 mg Cr(III)/kg bw/day.

As trichromium dicarbide is practically insoluble, the dermal route can be considered as irrelevant for reprotoxicity due to the low bioavailability of Cr.

Effects on developmental toxicity

Description of key information

No malformations were observed among the offspring of chromium(III) oxide treated rats (oral exposure, Cr2O3 baked in bread, fed for 60 days before mating). Based on this, oral intake of chromium(III) oxide would not cause developmental effects in the offspring. NOAEL is 1216 mg Cr(3+)/kg/day.

Effect on developmental toxicity: via oral route

Dose descriptor:

NOAEL

1 216 mg/kg bw/day

Additional information

No studies on teratogenic effects of trichromium dicarbide were available and therefore read-across to other substances was applied.

No malformations were observed among the offspring of female rats orally exposed to chromium(III) oxide during 60 days before mating (NOAEL 1216 mg/kg bw/day). Maternal treatment with 200 mg chromium chloride/kg bw/day during gestation days 6-17 did not either result in any signs of embryotoxicity/teratogenicity or maternal toxicity. No signs of maternal toxicity were either observed, a fact which decreases the relevance of the results, as it is quite evident that a higher dose would be needed to reach a level with a potential to cause developmental toxicity.

An in vitro Embryonic Stem Cell Test with chromium(III)chloride supports the lack of embryotoxicity. Chromium chloride is much more soluble in water than trichromium dicarbide, and as no reprotoxic effects were seen with this substance, it is unlikely that trichromium dicarbide, with a clearly lower bioavailability, would cause embryotoxicity/teratogenicity or maternal toxicity.

The dermal route is insignificant for toxicity to reproduction caused by trichromium dicarbide, as the substance is practically insoluble and is not absorbed from the skin to the systemic circulation. No inhalation studies were found.

Justification for classification or non-classification

Based on the the NOAEL and NOEAC values obtained with high chromium(III) oxide doses, there are no indications that chromium should be classified for toxicity to reproduction or for developmental toxicity.

Based on read-across, no classification is suggested for trichromium dicarbide.