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EC number: 296-473-8 | CAS number: 92704-41-1 The product of high temperature calcination (above 450°C (842°F)) of naturally occurring kaolin, a hydrated aluminum silicate, resulting in the evolution of water and the formation of new substances depending upon the calcination temperatures employed.
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
Endpoint summary
Administrative data
Description of key information
Oral:
NOAEL (male rats): 1760 - 3000 mg/kg bw/day (RA Syloid 244; 103 weeks)
NOAEL (female rats): 1780 - 3210 mg/kg bw/day (RA Syloid 244; 103 weeks)
Dermal:
No dermal repeated dose toxicity studies.
Inhalation:
NOAEC (rats): 1.3 mg/m³ (RA Aerosil 200; 13 weeks)
Key value for chemical safety assessment
Repeated dose toxicity: via oral route - systemic effects
Endpoint conclusion
- Dose descriptor:
- NOAEL
- 1 760 mg/kg bw/day
- Study duration:
- chronic
- Species:
- rat
Repeated dose toxicity: inhalation - systemic effects
Endpoint conclusion
- Dose descriptor:
- NOAEC
- 1.3 mg/m³
- Study duration:
- subchronic
- Species:
- rat
Additional information
Oral
There are no data available for Kaolin, calcined. However, some investigations on repeated dose toxicity by the oral route are available for silica gel, cryst.-free (Syloid 244). Similar to OECD 453 a combined chronic toxicity/carcinogenicity study was carried out (Takizawa et al. 1988, RL2). No particular adverse effects were observed in rats and mice treated with Syloid 244 lifelong at dietary level of 5%, corresponding to 1760 - 3000 mg/kg bw/day and 1780 - 3210 mg/kg bw/day for male and female rats, respectively and 5270 – 7490 mg/kg bw/day and 3950 – 13310 mg/kg bw/day for male and female mice, respectively .
In a feeding study, conducted similar to OECD 408, male and female rats received Syloid 244 for 26 weeks (Hackenberg 1975, RL2). No treatment-related findings were noted up to and including 8980 mg/kg bw/day. Isolated pathological findings were unrelated to dosing and common in untreated rats. No histopathological changes were observed in the kidneys and reproductive organs. The effect level (NOAEL) was 8980 and 7950 mg/kg bw/day for females and males, respectively.
Dermal
Repeated dose toxicity studies are not available for the dermal route.
Inhalation
There are no data available for Kaolin, calcined. However, some investigations on repeated dose toxicity by inhalation are available for structure-analogue substances. Several repeated dose inhalation studies have been conducted with synthetic amorphous silica, using various animal species, mostly rat, but also guinea pig and monkey. The exposure concentrations ranged between approx. 1 and 31 mg/m³.
A repeated dose inhalation study (13 weeks) including recovery intervals of up to one year, was carried out to investigate the effects of Aerosil 200 (pyrogenic synthetic amorphous silica). Dose-related changes caused by inflammatory reactions of the tissue were observed in the lung of animals exposed to the test material. Associated lesions only partly recovered during the one-year post-exposure period at the top exposure level. The level of 1.3 mg/m³ induced only slight changes, which generally disappeared quickly (cellular infiltration, stimulation of collagen production and increase in lung weight). Focal interstitial fibrosis was not noted directly after the exposure period of 3 months, but appeared with a delay in the 31 mg/m³ rats, and to a lesser degree, in the 5.9 mg/m³ group. Interestingly, all types of pulmonary lesions were more marked in males than in females. Treatment-related, microscopic changes in the nasal region were occasionally found at the end of the exposure period such as focal necrosis and slight atrophy of the olfactory epithelium (Reuzel et al. 1991, RL2).
In a short-term inhalation study programme, three synthetic amorphous silica (precipitated, pyrogenic, gel silica types) were investigated in comparison to a crystalline silica as positive control (Arts et al., 2003, RL2; Arts and Kuper, 2003, RL2). Wistar rats were exposed to 1, 5 and 25 mg/m³ (nominal concentration) of each silica for 5 days, 6 hours/day. Satellite groups were exposed correspondingly and kept for a recovery period of one and three months. The silica gel and the pyrogenic silica were only examined in males because they had proven to be more sensitive than females, as observed in the study of the precipitated silica.
The inhalation of respirable particles of synthetic amorphous silica (SAS) produces a time- and dose-related inflammation response of the lung tissue in animal studies. Progressive events following excess exposure are characterised as “interstitial fibrosis/early nodular fibrosis/incipient fibrosis”. However, a progression process of any lesion has not been observed like that seen after quartz exposure, i.e. all observations suggest reversibility. There are no signs of classical nodular silicosis or a lymphatic-type pneumoconiosis. On the other hand, crystalline silica produces persistent lung inflammation even at much lower exposure levels (Johnston et al., 2000, RL2).
For all tested synthetic amorphous silica a similar effect profile was determined. In general, the high exposure concentrations (25 mg/m³) induced dose-related effects which reflected an inflammatory response of the lung tissue, associated with a slight morphological tissue reaction (hypertrophy, partly hyperplasia of the bronchiolar epithelium). All observed changes disappeared or tended to disappear during the recovery period, showing clear signs of reversibility, while recovery was not observed in the positive control group (crystalline silica). For the precipitated silica (Zeosyl 45) and the silica gel (Syloid 74), effects at the mid-exposure concentration (5 mg/m³) were confined to very slight increases in the relative neutrophil count with a concomitant decrease in the relative macrophage count at the day after exposure. There were no morphological tissue changes. For the pyrogenic type (Cab-O-Sil M5), slight hypertrophy of the bronchiolar epithelium was noted also at the mid-dose level and a slight body weight loss for all tested concentration levels. No effects were noted at the low concentration levels (1 mg/m³) of Zeosyl 45 and Syloid 74.
Prolonged exposure of rats (3, 6 and 12 months), guinea pigs and monkeys (10 to 18 months) to 15 mg/m³ (total dust) precipitated, pyrogenic and gel silica produced effects including impairment of lung function, clear inflammatory reactions with signs of early nodular fibrosis (Groth et al., 1980, RL4). High deposition of synthetic amorphous silica was noted in macrophages in lung and tracheal lymph nodes of the monkeys, not or barely found in rat and guinea pig. Macrophage and mononuclear cell aggregation was found to be significantly more pronounced in monkeys (bronchioles, aleveolar ducts venules, arterioles) than in rats and guinea pigs. However, it has to be emphasised that this study is not assignable (RL4) because of very limited documentation of the rat and guinea pig studies and shortcomings in the monkey test (accidential preexposure to asbestos) but the results are useful in relation to finding of other studies.
Justification for classification or non-classification
Oral:
Based on data for structural analogue substances, no repeated dose oral toxicity is expected from the exposure to Kaolin, calcined. There is no need for classification according to DSD (67/548/EEC) or CLP (1272/2008/EC).
Dermal:
Repeated dose toxicity studies are not available for the dermal route.
Inhalation:
Based on data for structural analogue substances there is no need for classification of Kaolin, calcined according to DSD (67/548/EEC) or CLP (1272/2008/EC).
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