Chrome tungsten titanium buff rutile

Endpoint summary

Description of key information

Short description of key information on bioaccumulation potential result:

The assessment for Chrome tungsten titanium buff rutile; CAS-no. 68186-92-5; C.I. Pigment Yellow 163 is based on a Read-Across from studies conducted on two chemically closely related rutile pigments.

Absorption

Nickel rutile (C.I. Pigment Yellow 53 (CAS no.8007-18-9))

rat oral, 90 d: no relevant metal levels in studied organs (Bomhard et al. 1982)

rat inhalation, 5 d: no relevant metal ion levels in studied organs; lung clearance half-time: 50 d (BASF 1994)

Chrome rutile (C.I. Pigment Brown 24 (CAS no. 68186-90-3))

rat oral, 90 d: no relevant metal levels in studied organs lung clearance half-time: 50 d (Bomhard et al. 1982)

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

Bioaccessibility in 5 artificial physiologial test media:

The bioaccessibility of “Chromium titanium tungsten buff rutile” been investigated experimentally in vitro by simulating dissolution under physiological conditions considered to mimic the most relevant exposure routes (oral, dermal and inhalation), as follows:

- Gamble’s solution (GMB, pH 7.4) which mimics the interstitial fluid within the deep lung under normal health conditions,

- phosphate-buffered saline (PBS, pH 7.2), which is a standard physiological solution that mimics the ionic strength of human blood serum,

- artificial sweat (ASW, pH 6.5) which simulates the hypo osmolar fluid, linked to hyponatraemia (loss of Na+ from blood), which is excreted from the body upon sweating,

- artificial lysosomal fluid (ALF, pH 4.5), which simulates intracellular conditions in lung cells occurring in conjunction with phagocytosis and represents relatively harsh conditions and

- artificial gastric fluid (GST, pH 1.5), which mimics the very harsh digestion milieu of high acidity in the stomach.

In five different artificial physiological media, up to 0.03 % titanium, (i.e., GST; pH 1.5 & ALF; pH 4.5), 0.045 % chromium (GST; pH 1.5) and 0.62 % tungsten (i.e., ALF; pH 4.5) of “Chromium titanium tungsten buff rutile” was dissolved depending on solution parameters and test duration.

Results from repeated dose studies with the analogous chrome rutile (CAS 68186-90-3; oral, 90 d rat) and nickel rutile (CAS 8007-18-9; oral 90 d rat, inhalation 5 d rat) suggest that the substance is not bioavailable.

Nickel rutile

In an OECD guideline 408 compliant subchronic study, five male and five female Wistar rats were administered 0.45, 4.5, 45 and 450 mg/kg bw/day for 90 d (Bomhard et al. 1982). Antimony levels were slightly above detection limits in kidneys and liver, whereas no measurable nickel levels were detected. In a GLP compliant bioavailability study, male Wistar rats were exposed for 5 d to 60 mg/m3 test substance; the observation period was 0, 3, 10, 31 and 60 d (BASF 1994). Nickel and antimony levels in the lung declined following first-order kinetics with a clearance half-life of 50 d. In liver and kidneys, antimony and nickel were present in the range of the limit of quantification or below, with the exception of a clear Ni peak in the kidneys on day 3 of the post-exposure period. This peak can hardly be explained physiologically and a contamination with Ni during the processing steps by an unknown Ni source cannot be excluded. In conclusion, study results indicate a negligible bioavailability of Ni and Sb after inhalation of the test substance.

Chrome rutile

Comparable results as in the 90 d oral rat study with the nickel rutile (Bomhard et al. 1982)