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EC number: 235-120-4
CAS number: 12070-08-5
No substance specific data on repeated dose toxicity is available
for titanium carbide. Due to similar physico-chemical properties,
similar or lower transformation/dissolution results and similar or lower
in vitro bioaccessibility in synthetic body fluids compared to titanium
dioxide, data from TiO2 can be used for read-across.
Available data on repeated inhalation exposure of rats to titanium
dioxide, especially those of the 2-year inhalation
toxicity/carcinogenicity study, allowed a derivation of NOAEC values for
non-neoplastic adverse and neoplastic effects after chronic exposure to
pigment grade titanium dioxide. Two-year inhalation exposure in male and
female Sprague-Dawley rats to 10, 50, or 250 mg/m³ of titanium dioxide
(Lee et al., 1985) resulted in a dose- and time-dependent deposition of
titanium dioxide in the lungs leading to a marked impairment of lung
clearance. The continued exposure to titanium dioxide within the lungs
was associated with a dose-related dust cell accumulation, a foamy
macrophage response, type II pneumocyte hyperplasia, alveolar
proteinosis, alveolar bronchiolarisation, cholesterol granuloma
formation, focal pleurisy and collagenised fibrosis at exposure to 50
and 250 mg/m³ of titanium dioxide. Based on these findings, a NOAEC of
10 mg/m³ was derived for fibrogenic (non-neoplastic) effects in the
lung. Another chronic study in mice, rats and hamsters (Bermudez, 2002)
indicate that a concentration of 50 mg/m³ already elicits a particle
overload in rats. Thus, the LOAEL is considered to be over-conservative
for humans. Instead of deriving a long-term DNEL for the inhalation
route the general dust level has been used. The median value of particle
size of titanium carbide was determined to be 2.13 µm. Thus, the general
dust limit of 3 mg/m³ for respirable particles has been applied
according to ECHA guidance on information requirements and chemical
safety assessment, Chapter R.8: Characterisation of dose
[concentration]-response for human health, chapter R.8.7.1.
For other workplaces where the nature of the aerosols corresponds
largely to the definition of the inhalable/respirable fraction, the
application of this DNEL warrants an intrinsic conservatism.
The available data in rats and mice clearly suggest that ingested
titanium dioxide is neither toxic nor carcinogenic to both species: In
the NCI carcinogenicity study, Fischer 344 rats and B6C3F1 mice were fed
diets containing 0, 25000 and 50000 ppm titanium dioxide for 103 weeks
(NCI 1979). Based on the histopathological examination, titanium dioxide
was considered to be neither toxic nor carcinogenic to rats and mice.
Thus, the highest dietary concentration of 50000 ppm titanium dioxide is
representing the NOAEL which corresponds to a dose of 3500 mg titanium
dioxide/kg bw/d for rats. Therefore, the oral NOAEL of 3500 mg of
titanium dioxide/kg bw/d for chronic toxicity in rats is used as dose
descriptor for the calculation of a DNEL for systemic effects for humans
exposed orally to comparable titanium compounds, like titanium dioxide.
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