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Methidathion (Ref: ENT 27193 )
Last updated: 19/02/2021
(Also known as: OMS 844)

SUMMARY
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; Fish acute ecotoxicity: High; Daphnia acute ecotoxicity: High; Bees acute contact ecotoxicity: High; Earthworms acute ecotoxicity: High
Human health
High alert:
Mammals acute toxicity: High; Acetyl cholinesterase inhibitor; Neurotoxicant
GENERAL INFORMATION
Description
An insecticide and acaricide used to control a wide range of chewing and sucking pests
Example pests controlled
Scales; Spider mites; Bollworm; Budworm; Lygus bugs; Whitefly
Example applications
Sunflower; Artichokes; Apples; Almonds; Cherries; Citrus; Sorghum; Cotton; Alfalfa
Efficacy & activity
-
Availability status
Current
Introduction & key dates
circa 1968
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
Portugal
Date EC 1107/2009 inclusion expires
Expired
EU Candidate for substitution (CfS)
-
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
Australia, USA
Chemical structure
Isomerism
-
Chemical formula
C₆H₁₁N₂O₄PS₃
Canonical SMILES
COC1=NN(C(=O)S1)CSP(=S)(OC)OC
Isomeric SMILES
No data
International Chemical Identifier key (InChIKey)
MEBQXILRKZHVCX-UHFFFAOYSA-N
International Chemical Identifier (InChI)
InChI=1S/C6H11N2O4PS3/c1-10-5-7-8(6(9)16-5)4-15-13(14,11-2)12-3/h4H2,1-3H3
2D structure diagram/image available?
Yes
Cambridge Crystallographic Data Centre diagrams
Common Name Relationship Link
methidathion -
General status
Pesticide type
Insecticide, Acaricide
Substance group
Organophosphate
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Synthetic
Mode of action
Non-systemic with contact and stomach action. Cholinesterase inhibitor.
CAS RN
950-37-8
EC number
213-449-4
CIPAC number
193
US EPA chemical code
100301
PubChem CID
13709
Molecular mass
302.3
PIN (Preferred Identification Name)
-
IUPAC name
3-dimethoxyphosphinothioylthiomethyl-5-methoxy-1,3,4-thiadiazol-2(3H)-one
CAS name
S-((5-methoxy-2-oxo-1,3,4-thiadiazol-3(2H)-yl)methyl) O,O-dimethyl phosphorodithioate
Other status information
Marine Pollutant; Chemical subject to PIC regulations
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
Aedes nigromaculis, Aphis gossypii, Bemisia tabaci, Meligethes aeneus, Myzus persicae, Plutella xylostella, many more
Physical state
Colourless crystals
Formulations
Property
Value
Example manufacturers & suppliers of products using this active now or historically
  • Cobra
  • Cobracide
  • Suprathion
  • Supracide
  • Ultracid
  • Ultracide
Example products using this active
  • King Tech Corp
  • Makhteshim Agan
  • Syngenta
  • Ciba Geigy
Formulation and application details
Usually supplied as an emulsifiable concentrate or wettable powder
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
240
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Moderate
Solubility - In organic solvents at 20 °C (mg l⁻¹)
150000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Ethanol
-
670000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Acetone
-
11000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Hexane
-
14000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
n-Octanol
-
Melting point (°C)
39.5
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
Boiling point (°C)
- - -
Degradation point (°C)
- - -
Flashpoint (°C)
- - -
Octanol-water partition coefficient at pH 7, 20 °C
P
3.72 X 1002 Calculated -
Log P
2.57
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Low
Bulk density (g ml⁻¹)
1.51
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)
0.25
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Low volatility
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
3.30 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)
10
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Non-persistent
DT₅₀ (lab at 20 °C)
10
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Non-persistent
DT₅₀ (field)
7
X3 X = WINPST database (click here )
3 = Unverified data of known source
Non-persistent
DT₉₀ (lab at 20 °C)
- - -
DT₉₀ (field)
- - -
DT₅₀ modelling endpoint
- - -
Note
Lab and field studies DT₅₀ range 3-18 days
Dissipation rate RL₅₀ on plant matrix
Value
5.0
R4 R = Peer reviewed scientific publications
4 = Verified data
-
Note
Published literature RL₅₀ range 0.45-11.36 days, 6 field & undercover grown crops, various matrices, n=7
Dissipation rate RL₅₀ on and in plant matrix
Value
6.5
R4 R = Peer reviewed scientific publications
4 = Verified data
-
Note
Published literature RL₅₀ range 1.5-12.6 days, 3 field & undercover grown crops, various matrices, n=5; Grapes in cold storage RL₅₀=64 days.
Aqueous photolysis DT₅₀ (days) at pH 7
Value
14
Q3 Q = Miscellaneous internet resources
3 = Unverified data of known source
Slow
Note
-
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
27
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Non-persistent
Note
-
Water-sediment DT₅₀ (days)
70
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Moderately fast
Water phase only DT₅₀ (days)
6
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Moderately fast
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd
-
G3 G = Extension Toxicology network database EXTOXNET (click here )
3 = Unverified data of known source
Moderately mobile
Koc
400
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
1.18 Calculated Low leachability
SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate
Value
9.23 X 10-03 Calculated -
Note
-
Potential for particle bound transport index
Low Calculated -
Potential for loss via drain flow
Moderately mobile Calculated -
ECOTOXICOLOGY
Property
Value
Source; quality score; and other information
Interpretation
Bio-concentration factor
BCF (l kg⁻¹)
12.6
R3 R = Peer reviewed scientific publications
3 = Unverified data of known source
Low potential
CT₅₀ (days)
Not available -
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
25
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)
0.2
L2 L = Pesticide manuals and hard copy reference books / other sources
2 = Unverified data of unknown source
Rat 2 year
High
(ppm diet)
4 -
Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)
- - -
Birds - Acute LD₅₀ (mg kg⁻¹)
23.6
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Anas platyrhynchos
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)
0.01
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Oncorhynchus mykiss
High
Fish - Chronic 21 day NOEC (mg l⁻¹)
- - -
Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
0.0064
J4 J = Pesticide Action Network database (click here )
4 = Verified data
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
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)
> 0.2
P3 P = Other governments and regulators
3 = Unverified data of known source
Chlorella pyrenoidosa
Moderate
Honeybees (Apis spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
> 0.13
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
High
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)
- - -
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 pollinators (1)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
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)
5.6
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Eisenia foetida
High
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
Harmful
AA2 AA = IOBC Database on classification of side effects to beneficial organisms, 2005
2 = Unverified data of unknown source
Typhlodromus pyri
-
Other arthropod (2)
LR₅₀ g ha⁻¹
- - -
% Effect
Harmful
AA2 AA = IOBC Database on classification of side effects to beneficial organisms, 2005
2 = Unverified data of unknown source
Chrysoperla carnea
-
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)
25
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)
200
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rabbit
-
Mammals - Inhalation LC₅₀ (mg l⁻¹)
0.14
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
-
Other Mammal toxicity endpoints
- - -
ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)
0.001
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
JMPR 1997
-
ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)
0.01
B4 B = UK CRD and ACP evaluation documents / and other Defra (UK) documents (click here )
4 = Verified data
UK ACP 1999
-
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
May be absorbed through the skin
MRLs
European
EU MRL pesticide database 
Notes
-
Drinking Water Standards
- - -
Drinking Water MAC (μg l⁻¹)
- - -
Health issues
Specific human health issues
Carcinogen
Genotoxic
Endocrine disruptor
?Possibly, status not identified
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
;
E3 E = Unspecified genotoxicity type (miscellaneous data source)
3 = Negative
No data found
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
XNo, known not to cause a problem
Yes, known to cause a problem
No data found
Eye irritant Phototoxicant  
XNo, known not to cause a problem
No data found  
General human health issues
Possible nervous system, liver, gall bladder and ovaries toxicant
USEPA - possible human carcinogen
Handling issues
Property
Value and interpretation
General
IMDG Transport Code is 6.1
CLP classification 2013
Health: H300, H302
Environment: H400, H410
EC Risk Classification
T+ - Very toxic: R28
Xn - Harmful: R21
N - Dangerous for the environment: R50, R53
EC Safety Classification
S1/2, S22, S28, S36/37, S45, S60, S61
WHO Classification
Ib (Highly hazardous / Highly hazardous)
UN Number
2783
Waste disposal & packaging
-
TRANSLATIONS
Language
Name
English
methidathion
French
methidathion
German
Methidathion
Danish
methidathion
Italian
metidation
Spanish
metidation
Greek
methidathion
Polish
metydation
Swedish
-
Hungarian
-
Dutch
methidathion

Record last updated: 19/02/2021
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