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Demeton-S-methyl
(Also known as: methyl-mercaptophos-teolovy; methyl demeton; mercapthphos)
SUMMARY
Demeton-S-methyl is an insecticide and acaricide. It is highly soluble in water, volatile and, based on its physico-chemical data, it is not expected to leach to groundwater. It is not persistent in soil systems. Demeton-S-methyl is highly toxic to mammals, a cholinesterase inhibitor, a neurotoxin and a recognised irritant. It is highly toxic to birds, aquatic invertebrates and honey bees and moderately toxic to most other species including fish and earthworms.
Data alerts

The following alerts are based on the data in the tables below. An absence of an alert does not imply the substance has no implications for human health, biodiversity or the environment but just that we do not have the data to form a judgement.

Environmental fate Ecotoxicity Human health
Environmental fate
Moderate alert:
Drainflow: Moderately mobile
Ecotoxicity
High alert:
Birds acute ecotoxicity: High; Daphnia acute ecotoxicity: High; Bees acute oral ecotoxicity: High
Human health
High alert:
Mammals acute toxicity: High; Acetyl cholinesterase inhibitor; Neurotoxicant
GENERAL INFORMATION
Description
An insecticide used to control aphids and other sucking insects on a range of crops
Example pests controlled
Aphids including woolly aphids, citrus aphids, Russian aphids; Sawflies; Bryobia mites; Lacebugs
Example applications
Vegetables including beans, peas, brassicas, peppers, aubergines, onions; Fruit including olives, peaches, plums, apricots; Tomatoes; Cotton; Peanuts; Wheat; Maize; Sorghum
Efficacy & activity
-
Availability status
-
Introduction & key dates
1957
UK regulatory status
UK COPR regulatory status
Not approved
Date COPR inclusion expires
Expired
UK LERAP status
No UK approval for use
EC Regulation 1107/2009 (repealing 91/414)
EC Regulation 1107/2009 status
Not approved
Dossier rapporteur/co-rapporteur
Not applicable
Date EC 1107/2009 inclusion expires
Expired
EU Candidate for substitution (CfS)
Not applicable
Listed in EU database
Yes
Approved for use (✓) under EC 1107/2009 in the following EU Member States
ATAustria
BEBelgium
BGBulgaria
CYCyprus
CZCzech Republic
DEGermany
DKDenmark
EEEstonia
ELGreece
                 
ESSpain
FIFinland
FRFrance
HRCroatia
HUHungary
IEIreland
ITItaly
LTLithuania
LULuxembourg
                 
LVLatvia
MTMalta
NLNetherlands
PLPoland
PTPortugal
RORomania
SESweden
SISlovenia
SKSlovakia
                 
Approved for use (✓) under EC 1107/2009 by Mutual Recognition of Authorisation and/or national regulations in the following EEA countries
ISIceland
NONorway
                 
Additional information
Also used in
-
Chemical structure
Isomerism
The methyl ester of the S-form of isomeric demeton
Chemical formula
C₆H₁₅O₃PS₂
Canonical SMILES
CCSCCSP(=O)(OC)OC
Isomeric SMILES
No data
International Chemical Identifier key (InChIKey)
WEBQKRLKWNIYKK-UHFFFAOYSA-N
International Chemical Identifier (InChI)
InChI=1S/C6H15O3PS2/c1-4-11-5-6-12-10(7,8-2)9-3/h4-6H2,1-3H3
2D structure diagram/image available?
Yes
General status
Pesticide type
Insecticide, Acaricide
Substance groups
Organophosphate insecticide; Organothiophosphate insecticide; Organophosphate acaricide; Organothiophosphate acaricide
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Synthetic
Mode of action
Systemic with contact and stomach action. Acetylcholinesterase (AChE) inhibitor.
CAS RN
919-86-8
EC number
213-052-6
CIPAC number
47
US EPA chemical code
-
PubChem CID
13526
CLP index number
015-031-00-5
Molecular mass
230.29
PIN (Preferred Identification Name)
S-[2-(ethylsulfanyl)ethyl] O,O-dimethyl phosphorothioate
IUPAC name
S-2-ethylthioethyl O,O-dimethyl phosphorothioate
CAS name
S-(2-(ethylthio)ethyl) O,O-dimethyl phosphorothioate
Other status information
PAN Bad Actor Chemical; Subject to the provisions of the UK Poisons Act 1972
Relevant Environmental Water Quality Standards
-
Herbicide Resistance Classification (HRAC)
Not applicable
Herbicide Resistance Classification (WSSA)
Not applicable
Insecticide Resistance Classification (IRAC)
1B
Fungicide Resistance Classification (FRAC)
Not applicable
Examples of recorded resistance
Aphis gossypii, Panonychus ulmi, Tetranychus urticae, Tetranychus viennensis, Aculus cornutus, Aphis craccivora, many others
Physical state
Yellow oil
Related substances & organisms
Formulations
Property
Value
Example manufacturers & suppliers of products using this active now or historically
  • Bayer CropScience
  • Doo Yang Industrial Co. Ltd.
Example products using this active
  • Metasystox
  • Duratox
  • DSM
  • Demeton EC
Formulation and application details
Usually supplied as an emulsifiable concentrate.
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
22000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 High
Solubility - In organic solvents at 20 °C (mg l⁻¹)
- - -
Melting point (°C)
- - -
Boiling point (°C)
- - -
Degradation point (°C)
- - -
Flashpoint (°C)
- - -
Octanol-water partition coefficient at pH 7, 20 °C
P
2.09 X 1001 Calculated -
Log P
1.32
G4 G = Extension Toxicology network database EXTOXNET. Available online but no longer updated. (click here )
4 = Verified data
 Low
Fat solubility of residues
Solubility
- - -
Data type
- - -
Density (g ml⁻¹)
1.21
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 -
Dissociation constant pKa) at 25 °C
- - -
-
Vapour pressure at 20 °C (mPa)
40
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 Highly volatile
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
4.19 X 10-04
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 Non-volatile
Maximum UV-vis absorption L mol⁻¹ cm⁻¹
- - -
Surface tension (mN m⁻¹)
- - -
Degradation
Property
Value
Source; quality score; and other information
Interpretation
General biodegradability
-
Soil degradation (days) (aerobic)
DT₅₀ (typical)
2.7
K4 K = Research datasets (e.g. Pandora, Demetra; these datasets no longer available). Norman Ecotoxicology database. (click here )
4 = Verified data
 Non-persistent
DT₅₀ (lab at 20 °C)
2.7
K4 K = Research datasets (e.g. Pandora, Demetra; these datasets no longer available). Norman Ecotoxicology database. (click here )
4 = Verified data
 Non-persistent
DT₅₀ (field)
- - -
DT₉₀ (lab at 20 °C)
- - -
DT₉₀ (field)
- - -
DT₅₀ modelling endpoint
- - -
Note
-
Dissipation rate RL₅₀ on plant matrix
Value
- - -
Note
-
Dissipation rate RL₅₀ on and in plant matrix
Value
3.0
R3 R = Peer reviewed scientific publications
3 = Unverified data of known source
 -
Note
Mango fruit, n=1
Aqueous photolysis DT₅₀ (days) at pH 7
Value
- - -
Note
-
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
56
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 Moderately persistent
Note
pH sensitive: DT₅₀ 63 days at pH 4, 8 days at pH 9 all at 22 °C
Water-sediment DT₅₀ (days)
- - -
Water phase only DT₅₀ (days)
- - -
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd
-
W3 W = French database provided by ARVALIS-Institut du Végétal. Dataset no longer available.
3 = Unverified data of known source
 Moderately mobile
Koc
90
Notes and range
-
Freundlich
Kf
- - -
Kfoc
-
1/n
-
Notes and range
-
pH sensitivity
-
Fate indices
Property
Value
Source; quality score; and other information
Interpretation
GUS leaching potential index
0.88 Calculated Low leachability
SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate
Value
1.95 X 10-03 Calculated -
Note
-
Potential for particle bound transport index
Low Calculated -
Potential for loss via drain flow
Moderately mobile Calculated -
Bio-concentration factor
BCF (l kg⁻¹)
0.5
R3 R = Peer reviewed scientific publications
3 = Unverified data of known source
Based on LogP < 3		 Low potential
CT₅₀ (days)
Not available -
Known soil metabolites
Metabolite
Major/Minor fraction
Estimated maximum occurrence fraction
Notes
demeton (Ref: ENT 17295)
- - -
Known groundwater metabolites

None

Other known metabolites

None
ECOTOXICOLOGY
Terrestrial ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
40
F4 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment )
4 = Verified data
Rat		 High
Mammals - Short term dietary NOEL
(mg kg⁻¹)
-
L2 L = Pesticide manuals and hard copy reference books / other sources
2 = Unverified data of unknown source
Rat 2 year		 -
(ppm diet)
1 -
Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)
- - -
Birds - Acute LD₅₀ (mg kg⁻¹)
44
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Coturnix japonica		 High
Birds - Short term dietary (LC₅₀/LD₅₀)
- - -
Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)
- - -
Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)
> 250
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Eisenia foetida		 Moderate
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)
2.6
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment )
3 = Unverified data of known source
Apis mellifera 24hr		 Moderate
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
> 0.19
K4 K = Research datasets (e.g. Pandora, Demetra; these datasets no longer available). Norman Ecotoxicology database. (click here )
4 = Verified data
Apis mellifera		 High
Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Chronic
- - -
Bumblebees (Bombus spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
> 2.68
R4 R = Peer reviewed scientific publications
4 = Verified data
Bombus terrestris 48 hr		 Moderate
-
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)
0.076
R4 R = Peer reviewed scientific publications
4 = Verified data
Megachile rotundata		 High
Mode of exposure
Contact
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)
Harmless
Q2 Q = Miscellaneous data from online sources
2 = Unverified data of unknown source
Typhlodromus pyri		 -
Beneficial insects (Ground beetles)
- - -
Aquatic ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
> 6.4
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Oncorhynchus mykiss		 Moderate
Fish - Chronic 21 day NOEC (mg l⁻¹)
- - -
Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
> 0.023
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Daphnia magna		 High
Aquatic invertebrates - Chronic 21 day NOEC (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)
22.1
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Scenedesmus subspicatus		 Low
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
10
Q2 Q = Miscellaneous data from online sources
2 = Unverified data of unknown source
Unknown species		 Low
Mesocosm study data
NOEAEC mg l⁻¹
- - -
NOEAEC mg l⁻¹
- - -
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)
40
F4 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment )
4 = Verified data
Rat		 High
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
30
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat		 -
Mammals - Inhalation LC₅₀ (mg l⁻¹)
0.13
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat (aerosol)		 -
Other Mammal toxicity endpoints
- - -
ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)
- - -
ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)
- - -
AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)
- - -
AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)
- - -
Dermal penetration studies (%)
- - -
Dangerous Substances Directive 76/464
List I; List II - -
Exposure Routes
Public
-
Occupational
-
MRLs
European
EU MRL pesticide database 
Great Britain
GB MRL Register 
Notes
-
Drinking Water Standards
- - -
Drinking Water MAC (μg l⁻¹)
- - -
Mammalian dose elimination route and rate
Rapidly eliminated in urine
G3 G = Extension Toxicology network database EXTOXNET. Available online but no longer updated. (click here )
3 = Unverified data of known source
 -
Health issues
Specific human health issues
Carcinogen
Genotoxic
Endocrine disruptor
XNo, known not to cause a problem
A3 A = Chromosome aberration (EFSA database)
3 = Negative
;
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
;
E1 E = Unspecified genotoxicity type (miscellaneous data source)
1 = Positive
XNo, known not to cause a problem
Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant
?Possibly, status not identified
✓Yes, known to cause a problem
✓Yes, known to cause a problem
Respiratory tract irritant Skin irritant Skin sensitiser
?Possibly, status not identified
✓Yes, known to cause a problem
 No data found
Eye irritant Phototoxicant  
✓Yes, known to cause a problem
 No data found  
General human health issues
No further information available
Handling issues
Property
Value and interpretation
General
Combustible
IMDG Transport Hazard Class 6.1
CLP classification 2013
Health: H301, H311
Environment: H411
WHO Classification
Ib (Highly hazardous)
UN Number
UN3018
Waste disposal & packaging
-
Shelf-life, storage, stability and reactivity
-
TRANSLATIONS
Language
Name
English
demeton-S-methyl
French
demeton-S-methyle
German
Demeton-S-methyl
Danish
demeton-S-methyl
Italian
demeton-s-metil
Spanish
demeton-S-metil
Greek
demeton-S-methyl
Polish
demeton-S-metylowy
Swedish
-
Hungarian
-
Dutch
demeton-S-methyl
Norwegian
-
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