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EC number: 275-735-5 | CAS number: 71630-92-7 Substance obtained by burning the husk removed from the rice paddy. Contains silica as well as the elements aluminum, calcium, carbon, chromium, copper, indium, iron, lead, magnesium, manganese, molybdenum, phosphorus, silver, sodium, tin, and zinc.
- 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
Toxicological Summary
- Administrative data
- Workers - Hazard via inhalation route
- Workers - Hazard via dermal route
- Workers - Hazard for the eyes
- Additional information - workers
- General Population - Hazard via inhalation route
- General Population - Hazard via dermal route
- General Population - Hazard via oral route
- General Population - Hazard for the eyes
- Additional information - General Population
Administrative data
Workers - Hazard via inhalation route
Systemic effects
Acute/short term exposure
DNEL related information
Local effects
Long term exposure
- Hazard assessment conclusion:
- DNEL (Derived No Effect Level)
- Value:
- 0.017 mg/m³
- Most sensitive endpoint:
- repeated dose toxicity
DNEL related information
- Overall assessment factor (AF):
- 3
- Dose descriptor:
- LOAEC
Acute/short term exposure
DNEL related information
Workers - Hazard via dermal route
Systemic effects
Acute/short term exposure
DNEL related information
Workers - Hazard for the eyes
Additional information - workers
For the alveolar fraction (aerodynamic diameter <5 µm) of crystalline silica, epidemiological data indicate that the LOAEC (human) for silicosis is 0.05 mg/m³. Applying an assessment factor 3 to account for extrapolation from a LOAEC to a NAEC, results in a DNEL for the alveolar crystalline silica fraction of 0.017 mg/m³ [(0.05 mg/m³)/3]. No further assessment factors for workers are required as the LOAEC was determined from data of subjects occupationally exposed (8-10 h/day for a working lifetime) to respirable silica particles.
Comparable results are obtained from animal data. The lowest published toxic concentration for chronic inhalation exposure in rats is 0.74 mg/m³ (Muhle et al., 1991; NTP, 2009). Rats were exposed to crystalline silica particles (MMAD 1.4 µm) at that analytic concentration for 6 h/day, 5 days/week for 24 months.
A DNEL value for the alveolar fraction of crystalline silica is derived by applying the following corrections and assessment factors:
Step 1) Relevant dose descriptor |
LOAECrat= 0.74 mg/m³ |
Step 2) Modification of starting point Correction differences between experimental and human exposure conditions Correction for differences in 8-h inhalative volumes between workers in rest and workers under light activity |
(6 h/day)/(8 h/day)
6.7 m³/10 m³ |
Step 3) Assessment factors Interspecies Intraspecies Exposure duration Dose response Quality of data base |
2.5 5 1 3 1 |
DNEL value for the alveolar crystalline silica fraction |
0.01 mg/m³ (0.74 x [6/8] x [6.7/10] x [1/(2.5 x 5 x 3)]) |
For further calculations, the DNEL value of 0.017 mg/m³ obtained from human data is preferred.
As the above mentioned DNEL values applies for the alveolar fraction of crystalline silica particles, DNEL values for rice husk ashes as a whole are derived taking into account the content of respirable particles (≤5 µm) as well as the total silica and crystalline silica contents.
Chemical composition, granulometry and crystallinity data are available for 3 rice husk ash samples:
Sample |
Test substance 1 |
Test substance 2 |
Test substance 3 |
Silica content |
>94% |
>99% |
>95% |
Thereof, crystalline silica content |
1% |
73% |
57% |
Particles ≤5 µm |
99% |
11% |
10% |
Overall alveolar crystalline silica fraction (assuming homogeneous distribution of crystalline material throughout all particle size fractions) |
0.009 |
0.08 |
0.054 |
This results in the following DNELs derived for whole rice husk ashes:
Sample |
Test substance 1 |
Test substance 2 |
Test substance 3 |
NAEC for alveolar crystalline silica (mg/m³) |
0.017 |
0.017 |
0.017 |
Alveolar crystalline silica fraction in rice husk ashes |
0.009 |
0.08 |
0.054 |
DNEL for rice husk ashes (mg/m³) |
1.89 |
0.213 |
0.315 |
The most critical DNEL value of 0.213 mg/m3(test substance 2) is used for the CSA.
General Population - Hazard via inhalation route
Systemic effects
Acute/short term exposure
DNEL related information
Local effects
Acute/short term exposure
DNEL related information
General Population - Hazard via dermal route
Systemic effects
Acute/short term exposure
DNEL related information
General Population - Hazard via oral route
Systemic effects
Acute/short term exposure
DNEL related information
General Population - Hazard for the eyes
Additional information - General Population
Since exposure for the general public is precluded, DNELs for the general population are not relevant and thus not derived.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
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