Slags, ferrochromium-manufg.

Endpoint summary

Description of key information

There are no repeated dose toxicity studies on ferrochromium slags and therefore data on silicates are used for read-across. 
The toxicity of the metal anions is assumed to be negligible because of their low solubility. Even if the inhaled dust were pure chromium, the toxicity would be low, without systemic effects. 
The experimental repeated dose toxicity by inhalation or by oral route of the read-across materials (calcium silicate, sodium aluminium silicate, kaolin (an Al-silicate), nonfibrous glass (containing Ca-, Al, Mg- and borosilicates) and silica gel) has appeared to be low.

Additional information

There are no repeated dose toxicity studies on ferrochromium slag. The amorphous glass phase of FeCr-slag consists of practically insoluble silicates, and therefore it is seen justified to use read-across to studies on synthetic amorphous silica, calcium silicate, sodium aluminium silicate, kaolin (an Al-silicate) and nonfibrous glass (containing Ca-, Al, Mg- and borosilicates).

An effects profile similar to the read-across materials is supposed to hold also for ferrochromium slag. This is based on the assumption that the particle size and morphology rather than particle composition is the determinant of inflammatory response in the lung. This implies that FeCr slag would not provoke a more severe pulmonary response under same test conditions.

The toxicity of the metal anions is assumed to be negligible because of their low solubility. Even if the inhaled dust were pure chromium, the toxicity would be low. The subchronic LOAEC for chromium(III) oxide is 4.4 mg/m³(corresponding to 3 mg Cr(III) /m³), and the severity and frequency of inflammatory changes in the lungs were minimal. No systemic adverse effects were observed in the inhalation study. However the release of Cr for FeCr slag is very low, and therefore the the critical effects should be based on the amorphous glass phase and particle effects.

No significant pathological lung effects attributable to occupational long-term exposure to synthetic amorphous silicates have been reported, and no signs of pneumoconiosis, silicosis and fibrosis were evident.

The experimental repeated dose toxicity by inhalation or by oral route of the read-across materials has appeared to be low.

Nonfibrous glass dust (17–19 mg/m³) and kaolin (23–27 mg/m³) have induced only minimal pulmonary changes without fibrosis when rats or guinea pig were exposed for a year. In another study, no toxicity was observed in rats, which were exposed to kaolin at 10 mg/m³for up to 12 months. Calcium silicate (three commercial grades) exposed (10 mg/m³) rats had perinuclear fibrotic nodules when exposed to one of the materials. The effect was, however, supposed to be caused by the detected quartz contents of the lung.  

After long-term (2 years) oral application in the diet of rats and mice, no adverse effects were demonstrable for silica gel. There were no biological or any other meaningful alterations in body weight, food consumption or physical features of the exposed animals. No significant dose-related effects were seen at any dose level upon clinical laboratory examinations. The pathological examinations revealed no gross or microscopic changes in the tissues examined.

Following feeding of 0.625 to 10 % sodium aluminium silicate in the diet for 14 days, only occasional growth depression or slight elevation of organ weights were observed at the highest doses.

Justification for classification or non-classification

No classification for repeated dose toxicity is suggested because of low toxicity seen in animals and also the observations in workers exposed to the read-across materials do suggest low toxicity.