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Diquat dichloride
Last updated: 17/01/2021
(Also known as: diquat; deiquat; reglone)

SUMMARY
Diquat dibromide is an EU approved contact desiccant and herbicide. It is highly soluble in water, has a low risk of leaching to groundwater and is volatile. It is very persistent in soil but rapidly degrades in aquatic systems. It is moderately toxic to mammals and is a known irritant but no other significant human health issues have been identified. It is moderately toxic to birds, most aquatic organisms, honeybees 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
High alert:
Very persistent
Warning:
Significant data are missing
 
Human health
Moderate alert:
Mammals acute toxicity: Moderate
GENERAL INFORMATION
Description
A non-residual bupyridyl herbicide and crop desiccant used mainly to control broad-leaved weeds and grasses
Example pests controlled
Water lettuce; Water hyacynth; Duckweed; Pennywort; Annual bluegrass; Fescue; Henbit; Buttercup
Example applications
Potatoes; Oilseed rape; Fruit including apples, pears, peaches, plums, citrus, olive, grapes; Tomatoes; Sunflowers; Vegetables including beans & peas, carrots, onions, chicory; Sugarbeet
Efficacy & activity
-
Availability status
Current
Introduction & key dates
1958, first reported
UK regulatory status
UK COPR regulatory status
Not approved
Date COPR inclusion expires
Expired
UK LERAP status
None
EC Regulation 1107/2009 (repealing 91/414)
EC Regulation 1107/2009 status
Not approved
Dossier rapporteur/co-rapporteur
UK/Sweden
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
                 
Additional information
Also used in
-
Chemical structure
Isomerism
None
Chemical formula
C₁₂H₁₂Cl₂N₂
Canonical SMILES
-
Isomeric SMILES
No data
International Chemical Identifier key (InChIKey)
SKYNPRKUXHXZFJ-UHFFFAOYSA-L
International Chemical Identifier (InChI)
InChI=1S/C12H12N2.2ClH/c1-3-7-13-9-10-14-8-4-2-6-12(14)11(13)5-1;;/h1-8H,9-10H2;2*1H/q+2;;/p-2
2D structure diagram/image available?
Yes
General status
Pesticide type
Herbicide
Substance group
Bipyridylium
Minimum active substance purity
95% w/w
Known relevant impurities
EU dossier - dibromoethane; 2,2-bipyridine; terpyridine & related isomers
Substance origin
Synthetic
Mode of action
Non-selective, contact absorbed through foliage, some desiccant action. Photosystem I (electron transport) inhibitor.
CAS RN
4032-26-2
EC number
-
CIPAC number
-
US EPA chemical code
-
PubChem CID
-
Molecular mass
255.14
PIN (Preferred Identification Name)
6,7-dihydrodipyrido[1,2-a:2′,1′-c]pyrazine-5,8-diium dichloride
IUPAC name
9,10-dihydro-8a,10a-diazoniaphenanthrene dichloride
CAS name
6,7-dihydrodipyrido[1,2-a:2′,1′-c]pyrazinediium dichloride
Other status information
Potential groundwater contaminant; PAN listed Highly Hazardous Chemical
Relevant Environmental Water Quality Standards
-
Herbicide Resistance Classification (HRAC)
D
Herbicide Resistance Classification (WSSA)
22
Insecticide Resistance Classification (IRAC)
Not applicable
Fungicide Resistance Classification (FRAC)
Not applicable
Examples of recorded resistance
-
Physical state
Crystalline solid
Related substances & organisms
Formulations
Property
Value
Example manufacturers & suppliers of products using this active now or historically
  • AgriGuard
  • Clayton
  • Standon
  • Syngenta
  • ICI Plant Protection
Example products using this active
  • Reglone
  • Retro
  • Quad
  • Googly
  • Weedol
  • Reglox
Formulation and application details
Often supplied as a soluble concentrate, gel or liquid concentrate
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
- - -
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
- - -
Log P
- - -
Bulk density (g ml⁻¹)
- - -
Dissociation constant pKa) at 25 °C
Not applicable
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
-
No dissociation
Vapour pressure at 20 °C (mPa)
- - -
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
- - -
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)
- - -
DT₅₀ (lab at 20 °C)
- - -
DT₅₀ (field)
5500
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
Very persistent
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
- - -
Note
-
Aqueous photolysis DT₅₀ (days) at pH 7
Value
- - -
Note
-
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
Stable
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
Stable
Note
Stable pH 5 to pH 9
Water-sediment DT₅₀ (days)
- - -
Water phase only DT₅₀ (days)
- - -
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd
- - -
Koc
-
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
- - -
SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate
Value
Cannot be calculated - -
Note
-
Potential for particle bound transport index
- - -
Potential for loss via drain flow
- - -
Key metabolites
Metabolite
Formation medium
Estimated maximum occurrence fraction
1107/2009 relevancy
1-oxo-1,2,3,4-tetrahydropyrido(1,2-a)pyrazin-5-ium (Ref: R32245)
Soil 0.099 Minor fraction; Relevant
ECOTOXICOLOGY
Property
Value
Source; quality score; and other information
Interpretation
Bio-concentration factor
BCF (l kg⁻¹)
- - -
CT₅₀ (days)
- -
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
1000
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
Rat
Moderate
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)
- - -
Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
- - -
Fish - Chronic 21 day NOEC (mg l⁻¹)
- - -
Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
- - -
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)
- - -
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
- - -
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)
- - -
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)
- - -
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
- - -
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)
1000
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
Rat
Moderate
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
2000
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
Rat
-
Mammals - Inhalation LC₅₀ (mg l⁻¹)
> 0.5
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
Rat
-
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
- - -
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)
- - -
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
;
B3 B = DNA damage/repair (EFSA database)
3 = Negative
;
C3 C = Gene mutation (EFSA database)
3 = Negative
;
D0 D = Genome mutation (EFSA database)
0 = No data
;
E3 E = Unspecified genotoxicity type (miscellaneous data source)
3 = Negative
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
Yes, known to cause a problem
Yes, known to cause a problem
Eye irritant Phototoxicant  
Yes, known to cause a problem
No data found  
General human health issues
Potential liver, kidney, stomach and intestine toxicant
Fatal if inhaled
Handling issues
Property
Value and interpretation
General
IMDG Transport Code is usually 6.1 or 8
Corrosive to most metals & may form flammable and explosive H2 gas when in contact with aluminum
May decompose at high temperatures to form toxic gases
CLP classification 2013
Health: H302, H315,H317, H319, H330, H335, H372
Environment: H400, H410
EC Risk Classification
T+ - Very toxic: R26
T - Toxic: R48/25
Xn - Harmful: R22, R43
Xi - Irritant: R36/37/38
N - Dangerous for the environment: R50, R53
EC Safety Classification
S1/2, S28, S36/37/39, S45, S60, S61
WHO Classification
II (Moderately hazardous)
UN Number
2781 for active, products usually 1760
Waste disposal & packaging
Packaging Group III (minor danger)
TRANSLATIONS
Language
Name
English
diquat dichloride
French
-
German
-
Danish
-
Italian
-
Spanish
-
Greek
-
Polish
-
Swedish
-
Hungarian
-
Dutch
-

Record last updated: 17/01/2021
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