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Silica
Last updated: 01/06/2024
(Also known as: silox; constituent of diatomaceous earth; amorphous silica; crystalline silica)
SUMMARY
Silica is an inert, naturally occurring mineral used as a carrier in some pesticide products and is sometimes used as an insecticide to control crawling insects, acting via its abrasive and desiccant properties. It is moderately soluble in water and stable in the environment. It is generally considered non-toxic to biodiversity and humans. However, there are some concerns that exposure to crystalline silica particles that are small enough to reach the lungs can cause lung cancer.
GENERAL INFORMATION
Description
Inert mineral used as a carrier in some pesticide products and sometimes used as an insecticide to control crawling insects
Availability status
Current
Introduction & key dates
1956, silica gel first registered USA; 1960, silicon dioxide first registered US
Examples of veterinary uses
-
Examples of species treated
-
Approval status
VMR 2013/2033 approval status (GB/UK)
-
EU Regulatory approval status
-
Chemical structure
Isomerism
None
Chemical formula
SiO₂
Canonical SMILES
O=[Si]=O
Isomeric SMILES
-
International Chemical Identifier key (InChIKey)
VYPSYNLAJGMNEJ-UHFFFAOYSA-N
International Chemical Identifier (InChI)
InChI=1S/O2Si/c1-3-2
2D structure diagram/image available?
Yes
General status
Veterinary substance type
-
Other bioactivity & uses
Carrier
Substance groups
Inorganic compound
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Natural
Mode of action
Inert but acts as an insecticide via its abrasive and desiccant physical properties
Molecular targets
-
CAS RN
7631-86-9
EC number
231-545-4
CIPAC number
None allocated
US EPA chemical code
072605
PubChem CID
24261
CLP index number
No data found
Therapeutic Class
-
ATCvet Code
-
Controlled Drug?
-
Regulation 37/2010 MRL Classification
-
Molecular mass
60.08
PIN (Preferred Identification Name)
-
IUPAC name
dioxosilane
CAS name
silicon dioxide
Other status information
-
Relevant Environmental Water Quality Standards
-
Physical state
White powder
Formulations
Property
Product
Manufacturer
Authorisation Route
Legal Class (GB/UK)
Example products (past and present) using this active
- - - -
Formulation and application details
-
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
120
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
 Moderate
Solubility - In organic solvents at 20 °C (mg l⁻¹)
- - -
Melting point (°C)
1610
A5 A = EU regulatory and evaluation data as published by EC, EFSA (RAR, DAR & Conclusion dossiers), EMA (e.g. EU Annex III PIC DGD) (EU - Pesticides database; EFSA Scientific Publications )
5 = Verified data used for regulatory purposes
 -
Boiling point (°C)
- - -
Degradation point (°C)
- - -
Flashpoint (°C)
- - -
Octanol-water partition coefficient at pH 7, 20 °C
P
- - -
Log P
- - -
Fat solubility of residues
Solubility
- - -
Data type
- - -
Density (g ml⁻¹)
2.2
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
 -
Dissociation constant pKa) at 25 °C
- - -
-
Vapour pressure at 20 °C (mPa)
- - -
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
- - -
Volatilisation as max % of applied dose lost
From plant surface
- - -
From soil surface
- - -
Maximum UV-vis absorption L mol⁻¹ cm⁻¹
- - -
Surface tension (mN m⁻¹)
- - -
Refractive Index
- - -
Environmental release
-
Degradation
Property
Value
Source; quality score; and other information
Interpretation
Soil degradation (days) (aerobic)
DT₅₀ (typical)
730
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
 Very persistent
DT₅₀ (lab at 20 °C)
- - -
DT₅₀ (field)
- - -
DT₉₀ (lab at 20 °C)
- - -
DT₉₀ (field)
- - -
Note
Literature states that the substance is stable in soil
Manure DT₅₀ (days)
- - -
Aqueous photolysis DT₅₀ (days) at pH 7
Value
Stable
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
 Stable
Note
-
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
Stable
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
 Stable
Note
-
Water-sediment DT₅₀ (days)
Stable
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
 Stable
Water phase only DT₅₀ (days)
Stable
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
 Stable
Sediment phase only DT₅₀ (days)
- - -
Air degradation
As this parameter is not normally measured directly, a surrogate measure is used: ‘Photochemical oxidative DT₅₀’. Where data is available, this can be found in the Fate Indices section below.
Decay in stored produce DT₅₀
-
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd (mL g⁻¹)
- - -
Koc (mL g⁻¹)
-
Notes and range
-
Freundlich
Kf (mL g⁻¹)
- - -
Kfoc (mL g⁻¹)
-
1/n
-
Notes and range
-
pH sensitivity
-
Fate indices
Property
Value
Source; quality score; and other information
Interpretation
GUS leaching potential index
- - -
Bio-concentration factor
BCF (l kg⁻¹)
- - -
CT₅₀ (days)
- -
Known metabolites

None

ECOTOXICOLOGY
Terrestrial ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
5110
R3 R = Peer reviewed scientific publications
3 = Unverified data of known source
Rat		 Low
Mammals - Short term dietary NOEL
(mg kg⁻¹)
- - -
(ppm diet)
- -
Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)
- - -
Birds - Acute LD₅₀ (mg kg⁻¹)
- - -
Birds - Short term dietary (LC₅₀/LD₅₀)
- - -
Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)
- - -
Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)
- - -
Earthworms - Chronic NOEC, reproduction (mg kg⁻¹)
- - -
Soil micro-organisms
- - -
Collembola
Acute LC₅₀ (mg kg⁻¹)
- - -
Chronic NOEC (mg kg⁻¹)
- - -
Non-target plants
- - -
- - -
Honeybees (Apis spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Chronic
- - -
Notes
-
Bumblebees (Bombus spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
-
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
-
Mason bees (Osmia spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Other bee species (1)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
Other bee species (2)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
Beneficial insects (Ladybirds)
- - -
Beneficial insects (Lacewings)
- - -
Beneficial insects (Parasitic wasps)
- - -
Beneficial insects (Predatory mites)
- - -
Beneficial insects (Ground beetles)
- - -
Aquatic ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Temperate Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
- - -
Temperate Freshwater Fish - Chronic 21 day NOEC (mg l⁻¹)
- - -
Tropical Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
> 1000
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
Danio rerio		 Low
Temperate Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
> 1000
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
Daphnia magna		 Low
Temperate Freshwater Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)
- - -
Tropical Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
- - -
Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)
- - -
Sediment dwelling organisms - Acute 96 hour LC₅₀ (mg l⁻¹)
- - -
Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)
- - -
Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)
- - -
Aquatic plants - Acute 7 day EC₅₀, biomass (mg l⁻¹)
- - -
Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)
440
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
Pseudokirchneriella subcapitata		 Low
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
- - -
Mesocosm study data
NOEAEC mg l⁻¹
- - -
NOEAEC mg l⁻¹
- - -
Marine bivalves
- - -
HUMAN HEALTH AND PROTECTION
General
Property
Value
Source; quality score; and other information
Interpretation
Threshold of Toxicological Concern (Cramer Class)
High (class III) - -
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
5110
R3 R = Peer reviewed scientific publications
3 = Unverified data of known source
Rat		 Low
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
5000
R3 R = Peer reviewed scientific publications
3 = Unverified data of known source
Rabbit		 -
Mammals - Inhalation LC₅₀ (mg l⁻¹)
2.2
A4 A = EU regulatory and evaluation data as published by EC, EFSA (RAR, DAR & Conclusion dossiers), EMA (e.g. EU Annex III PIC DGD) (EU - Pesticides database; EFSA Scientific Publications )
4 = Verified data
Rat		 -
Other Mammal toxicity endpoints
- - -
ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)
None allocated
A5 A = EU regulatory and evaluation data as published by EC, EFSA (RAR, DAR & Conclusion dossiers), EMA (e.g. EU Annex III PIC DGD) (EU - Pesticides database; EFSA Scientific Publications )
5 = Verified data used for regulatory purposes
 -
ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)
None allocated
A5 A = EU regulatory and evaluation data as published by EC, EFSA (RAR, DAR & Conclusion dossiers), EMA (e.g. EU Annex III PIC DGD) (EU - Pesticides database; EFSA Scientific Publications )
5 = Verified data used for regulatory purposes
 -
AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)
- - -
AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)
0.3
A5 A = EU regulatory and evaluation data as published by EC, EFSA (RAR, DAR & Conclusion dossiers), EMA (e.g. EU Annex III PIC DGD) (EU - Pesticides database; EFSA Scientific Publications )
5 = Verified data used for regulatory purposes
as mg m³ (inhalation)		 -
Dermal penetration studies (%)
- - -
Dangerous Substances Directive 76/464
- - -
Exposure Routes
Public
Public may become exposed via their diets but substance is relatively benign by this route
Occupational
Serious risk to operators and other workers - PPE/PPC required
Mammalian dose elimination route and rate
- - -
Health issues
Specific human health issues
Carcinogen
Genotoxic
Endocrine disruptor
?Possibly, status not identified
A0 A = Chromosome aberration (EFSA database)
0 = No data
;
B0 B = DNA damage/repair (EFSA database)
0 = No data
;
C0 C = Gene mutation (EFSA database)
0 = No data
;
D0 D = Genome mutation (EFSA database)
0 = No data
;
E0 E = Unspecified genotoxicity type (miscellaneous data source)
0 = No data
XNo, known not to cause a problem
Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant
XNo, known not to cause a problem
XNo, known not to cause a problem
XNo, known not to cause a problem
Respiratory tract irritant Skin irritant Skin sensitiser
✓Yes, known to cause a problem
XNo, known not to cause a problem
?Possibly, status not identified
Eye irritant Phototoxicant  
✓Yes, known to cause a problem
 No data found  
General human health issues
Dust can cause silicosis and bronchitis
May cause sensitization via inhalation
US EPA have concluded that exposure to crystalline silica particles that are small enough to reach the lungs can cause lung cancer
Handling issues
Property
Value and interpretation
General
Prevent generation of dust
CLP classification 2013
Health: H315, H319, H332, H335}
WHO Classification
Not listed (Not listed)
UN Number
-
Waste disposal & packaging
-
Shelf-life, storage, stability and reactivity
-
TRANSLATIONS
Language
Name
English
silica
French
silice cristalline
German
kristallenes Silikon
Danish
siliciumdioxid
Italian
silicone cristallino
Spanish
silicona cristalina
Greek
-
Polish
krystaliczna krzemionka
Swedish
Kiseldioxid
Hungarian
-
Dutch
kristallijn kiezelzuur
Norwegian
-
Record last updated: 01/06/2024
Contact: aeru@herts.ac.uk
Please cite as: Lewis, K.A., Tzilivakis, J., Warner, D. and Green, A. (2016) An international database for pesticide risk assessments and management. Human and Ecological Risk Assessment: An International Journal, 22(4), 1050-1064. DOI: 10.1080/10807039.2015.1133242