Kaolin, calcined

Endpoint summary

Description of key information

Oral: 
LD50 (rats) > 5000 mg/kg bw (RA Kaolin clay; limit test)
Inhalation:
LC50 (rats) > 2.07 mg/L air (4 hours, limit test)
Dermal:
LD50 (rats) > 5000 mg/kg bw (RA Kaolin clay; 24 hours, limit test)

Additional information

Oral

No experimental data are available for Kaolin, calcined, but there are acute oral studies performed with the structurally related substances Kaolin clay, Silicic acid, aluminium salt and with the Fluid Cracking Catalysts (FCC) CCZ-44 and FCC CBZ-1, containing up to 45% Kaolin, calcined.

The acute oral toxicity of Kaolin clay was tested in a GLP-guideline study according to EPA OPP 81-1 (Engelhard Corp., 2010, RL2). The test substance was administered by gavage to five female and five male Sprague-Dawley rats at a fixed dose of 5000 mg/kg bw. During the observation period of 14 days, no mortality occured and no signs of toxicity were recorded. Thus, the oral LD50 is > 5000 mg/kg bw.

The acute oral toxicity of Silicic acid, aluminium salt was tested according to OECD guideline 423 (Colas, 2010, RL2). Six female rats received gavage a single dose of 2000 mg/kg bw of the test substance. No mortality occured during the observation period of 14 days and no signs of toxicity were recorded. Thus, the oral LD50 is > 2000 mg/kg bw. In accordance with OECD guideline 423, the LD50 cut-off of the test item may be considered higher than 5000 mg/kg bw for the oral route in the rat.

The acute oral toxicity of the FCC catalysts CCZ-44 and CBZ-1 were determined in a non-GLP study according to the guideline of the Department of Transportation, Code of Federal Regulations, Title 49, Part 173 (Calkins and Ward, 1976, RL2). Based on range finding results, ten albino rats each received one single dose of 31600 mg/kg bw of the test substances by gavage. No deaths were noted up to 48 hours after administration. Furthermore no signs of toxicity were observed. Thus, the oral LD50 for the FCC catalysts CCZ-44 and CBZ-1 is > 31600 mg/kg bw.

 

Inhalation

An acute inhalation study according to EPA OPP 81-3 was performed with dust powder of the read-across substance Kaolin, calcined (Engelhard Corp, 1997, RL1). Five male and five female Sprague-Dawley rats were exposed to 2.07 mg/L Kaolin, calcined in the air of whole body exposure chambers for 4 hours. The mass median aerodynamic diameter was estimated to be 2.5 microns, indicating respirable particles. No mortality occurred during14 days observation period. Clinical signs were ocular and nasal discharge, irregular respiration, hunched posture and hypoactivity during the exposure time. All rats recovered from these symptoms within 17 hours after exposure. Gross necropsy findings at terminal sacrifice revealed red foci on the surface of the lungs of one female. Apart from red lung discoloration consistent with CO2 inhalation (the euthanasia procedure), all other tissues and organs appeared normal. The LC50 is > 2.07 mg/L air.

 

Dermal

No data were located for Kaolin, calcined regarding acute dermal toxicity. But there are data available for structurally related compounds for this endpoint.

The acute dermal toxicity of Kaolin clay was examined in a GLP-guideline study according to EPA OPP 81-2 (Engelhard Corp., 1997, RL2). After acute dermal application of 5000 mg/kg bw of Kaolin, calcined as dry paste to the intact skin of five female and five male Sprague-Dawley rats for 24 hours under semiocclusive conditions, no signs of systemic or organ toxicity were recorded and no deaths occurred during 14 days observation period. The dermal LD50 is > 5000 mg/kg bw.

After acute dermal application of 2000, 3000, 4000 and 5000 mg/kg bw of silicic acid, aluminium salt (Zeolex 23A) as aqueous paste to the intact skin of 4 rabbits per dose for 24 hours under occlusive conditions, no signs of systemic or organ toxicity were recorded and no deaths occured. Dermal reactions were limited to slight erythema and edema which were fully reversible at the latest within 4 days. (Woltjen and Calkins, 1978, RL2). The dermal LD50 is > 5000 mg/kg bw.

The acute dermal toxicity of the FCC catalysts CCZ-44 and CBZ-1 were determined in a non-GLP study according to the guideline of the Department of Transportation, Code of Federal Regulations, Title 49, Part 173 (Calkins and Ward, 1976, RL2). The test substances were applied at 2000 mg/kg bw to the intact skin of 5 rabbits each for 24 hours under occlusive conditions. No deaths were noted up to 48 hours after application. The dermal LD50 is greater than 2000 mg/kg for FCC CCZ-44 and FCC CBZ-1.

 

Other routes

Following intratracheal inoculation of 0 or 5 mg of the read across substance Indian Kaolin in 0.1 mL NaCl the pulmonary fibrogenic response of the test substance was investigated in mice over a period of 210 days. The test substance incited acute inflammatory reaction at early periods followed by macrophage reaction, proliferation of fibroblasts and formation of focal fibrotic areas comprised of thick dense reticulination (grade II). However, the fibrotic lesions in mice at 210 days were quite different to that of nodular or diffuse interstitial fibrotic lesions described in Kaolin workers (Sahu et al., 1978, RL2).

Justification for classification or non-classification

Based on the results obtained, Kaolin, calcined does not fulfill the criteria to be classified for acute toxicity according to DSD (67/548/EEC) or CLP (1272/2008/EC).