Silicic acid, lithium magnesium sodium salt

Endpoint summary

Description of key information

A repeat dose 90 day oral toxicity test was carried out on rats in 1973. The study was not under GLP at that time but the testing was thorough and equivalent to that required by todays methodology. Three concentrations of Laponite (5mg/kg bw, 50mg/kg bw and 500mg/kg bw) were fed to rats on a daily basis. No relevant mortalities were noted in the low and medium level groups. Half of the rats in the high dose group died before the end of the test period due to a build up of the test substance as a gel in the thoracic cavity, stomach and intestinal tract. No significant effect on other organs / blood was observed at necropsy.
Repeat dose studies have not been carried out on test animals for dermal or inhalation routes of exposure and waivers have been justified for non testing.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEL

50 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Additional information

The oral study, carried out in 1973, was designed to evaluate the repeat dose oral toxicity of Laponite on rats over a period of 3 months. The reason for this testing at the time was to establish the safety of this material for use in domestic personal care products such as toothpaste.

The material was dispersed in deionised water and the rats were fed by intubation. The rats were split into four groups, even numbers of male/female. Group 1 was the control group, (just water), group 2 was low dose (5mg/kg bw), group 3 was medium dose (50mg/kg bw) and group 4 was high dose (500mg/kg bw). The high dose group saw some premature deaths and these were found to be due to the fact that the Laponite forms a gel at high dose and this had accumulated in the animals digestive system and had not been digested. This level of dosing would not be permitted under today's controls. For surviving rats at necropsy, there were no signs of abnormalities relating to the oral dosing of the Laponite. The high dosage group resulted in half of the rats failing to survive to completion of the test but all rats in the other two groups (with the exception of 1 in the low dose group whose death was not attributed to the treatment) all survived. No systemic toxic effect as ascertained by blood analysis and histopathological examination were observed, even in the high dose rats.