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Demeton-S-methyl
Last updated: 23/12/2020
(Also known as: methyl-mercaptophos-teolovy; methyl demeton; mercapthphos)

SUMMARY
Demeton-S-methyl is an insecticide not approved for use in the EU. 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.
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
Unknown
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
                 
Also used in
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 group
Organophosphate
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
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
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
Formulations
Property
Value
Example manufacturers & suppliers of products using this active now or historically
  • Metasystox
  • Duratox
  • DSM
  • Demeton EC
Example products using this active
  • Bayer CropScience
  • Doo Yang Industrial Co. Ltd.
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 (click here )
4 = Verified data
Low
Bulk 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
4 = Verified data
Non-persistent
DT₅₀ (lab at 20 °C)
2.7
K4 K = Research datasets, e.g. Pandora, Demetra
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
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 -
Key metabolites
Metabolite
Formation medium
Estimated maximum occurrence fraction
1107/2009 relevancy
demeton-S-methyl sulfone
Animal - -
ECOTOXICOLOGY
Property
Value
Source; quality score; and other information
Interpretation
Bio-concentration factor
BCF (l kg⁻¹)
0.5
R3 R = Peer reviewed scientific publications
3 = Unverified data of known source
(LogP < 3)
Low potential
CT₅₀ (days)
Not available -
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
40
F4 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents (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)
- - -
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)
- - -
Non-target plants
- - -
- - -
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
Scenedemus subspicatus
Low
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
10
Q2 Q = Miscellaneous internet resources
2 = Unverified data of unknown source
Unknown species
Low
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 (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
4 = Verified data
Apis mellifera
High
Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
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 pollinators (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 pollinators (2)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
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)
- - -
Other soil macro-organisms
Acute LC₅₀ (mg kg⁻¹)
- - -
Chronic NOEC (mg kg⁻¹)
- - -
Other arthropod (1)
LR₅₀ g ha⁻¹
- - -
% Effect
Harmless
AB1 AB = SELECTV Database
1 = Estimated data with little or no verification
Typhlodromus pyri
-
Other arthropod (2)
LR₅₀ g ha⁻¹
- - -
% Effect
- - -
Soil micro-organisms
- - -
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 (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)
0.0003
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
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
-
European MRLs
EU MRL pesticide database 
Drinking Water Standards
- - -
Drinking Water MAC (μg l⁻¹)
- - -
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
CLP classification 2013
Health: H301, H311
Environment: H411
EC Risk Classification
T - Toxic: R24/25
N - Dangerous for the environment: R51, R53
EC Safety Classification
S1/2, S28, S36/37, S45, S61
WHO Classification
Ib (Highly hazardous / Highly hazardous)
UN Number
Usually 3018
Waste disposal & packaging
-
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

Record last updated: 23/12/2020
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