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Pyrithiobac-sodium (Ref: DPX PE 350)
Last updated: 27/11/2019
(Also known as: KIH 2031)

SUMMARY
Pyrithiobac-sodium is a post-emergence herbicide without EU regulatory approval for use. It has a high aqueous solubility, is semi-volatile and, based on its chemical properties, it is very mobile and has high potential to leach to groundwater. It is generally moderately persistent in soil systems but tends to be non-persistent in aquatic systems. It has a low mammalian toxicity but may bioaccumulate. It shows a low to moderate level of toxicity to most biodiversity.
GENERAL INFORMATION
Description
Post-emergence control of broad-leaved weeds in cotton and other crops
Example pests controlled
Cocklebur; Goosefoot; Nightshade; Knotweed; Pigweed; Rocket; Shepherd's purse; Sunflower; velvetleaf; Morning glory; Purslane
Example applications
Cotton
Efficacy & activity
-
Availability status
Current
Introduction & key dates
1995, USA
UK regulatory status
UK approval status
Not approved
EC Regulation 1107/2009 (repealing 91/414)
EC Directive 91/414 Status
Not approved
Dossier rapporteur/co-rapporteur
Not applicable
Date inclusion expires
Not applicable
EU Candidate for substitution (CfS)
Not applicable
Listed in EU database
No
Approved for use (✓) or known to be used (#) in the following EU-27 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
Chemical structure
Isomerism
-
Chemical formula
C₁₃H₁0ClN₂NaO₄S
Canonical SMILES
COC1=CC(=NC(=N1)SC2=C(C(=CC=C2)Cl)C(=O)[O-])OC.[Na+]
Isomeric SMILES
No data
International Chemical Identifier key (InChIKey)
CNILNQMBAHKMFS-UHFFFAOYSA-M
International Chemical Identifier (InChI)
InChI=1S/C13H11ClN2O4S.Na/c1-19-9-6-10(20-2)16-13(15-9)21-8-5-3-4-7(14)11(8)12(17)18;/h3-6H,1-2H3,(H,17,18);/q;+1/p-1
2D structure diagram/image available?
Yes
General status
Pesticide type
Herbicide
Substance group
Pyrimidinyloxybenzoic analogue
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Synthetic
Mode of action
Causes tissue death. Inhibits plant amino acid synthesis - acetohydroxyacid synthase AHAS.
CAS RN
123343-16-8
EC number
-
CIPAC number
-
US EPA chemical code
078905
PubChem CID
23682187
Molecular mass
348.74
PIN (Preferred Identification Name)
sodium 2-chloro-6-[(4,6-dimethoxypyrimidin-2-yl)sulfanyl]benzoate
IUPAC name
sodium 2-chloro-6-(4,6-dimethoxypyrimidin-2-ylthio)benzoate
CAS name
sodium 2-chloro-6-[(4,6-dimethoxy-2-pyrimidinyl)thio]benzoate
Other status information
-
Relevant Environmental Water Quality Standards
-
Herbicide Resistance Classification (HRAC)
B
Herbicide Resistance Classification (WSSA)
2
Insecticide Resistance Classification (IRAC)
Not applicable
Fungicide Resistance Classification (FRAC)
Not applicable
Examples of recorded resistance
Amaranthus palmeri
Physical state
Off-white powder
Formulations
Property
Value
Example manufacturers & suppliers of products using this active now or historically
  • Stap
  • Staple
  • Staple LX
Example products using this active
  • DuPont
  • Kumiai Chemical Industry Co. Ltd.
UK LERAP status
No UK approval for use as a pesticide under EC Regulation 1107/2009
Formulation and application details
Usually supplied as a soluble powder
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
728000
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)
812
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Acetone
-
270000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Methanol
-
10
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
n-Hexane
-
205
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Ethyl acetate
-
Melting point (°C)
234
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
Boiling point (°C)
- - -
Degradation point (°C)
234
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
Flashpoint (°C)
- - -
Octanol-water partition coefficient at pH 7, 20 °C
P
1.45 X 10-01 Calculated -
Log P
-0.84
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Low
Bulk density (g ml⁻¹)
1.61
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
Dissociation constant pKa) at 25 °C
2.34
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
Strong acid
Vapour pressure at 20 °C
4.80 X 10-06
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
- - -
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
- - -
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)
60
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Moderately persistent
DT₅₀ (lab at 20 °C)
- - -
DT₅₀ (field)
- - -
DT₉₀ (lab at 20 °C)
- - -
DT₉₀ (field)
- - -
DT₅₀ modelling endpoint
- - -
Note
General literature data states DT₅₀ 60 days in silty soil. DT₅₀ 10 days for uplands and flooded soil. Main degradation route is microbial.
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
13
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Moderately fast
Note
pH sensitive: DT₅₀ 11 days at pH 5, 15 days at pH 9, all at 25 °C
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
Stable
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Stable
Note
-
Water-sediment DT₅₀ (days)
- - -
Water phase only DT₅₀ (days)
- - -
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd
0.5
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
-
Koc
-
Notes and range
General literature data gives Kd values ranging from 0.32 (sandy loam) to 0.75 (silty loam). Peered review study - Kd 0.22 to 0.59 L/kg
Freundlich
Kf
- - -
Kfoc
-
1/n
-
Notes and range
-
pH sensitivity
-
ECOTOXICOLOGY
Property
Value
Source; quality score; and other information
Interpretation
Bio-concentration factor
BCF (l kg⁻¹)
Low risk
Q3 Q = Miscellaneous internet resources
3 = Unverified data of known source
Based on LogP < 3
Low risk
CT₅₀ (days)
- -
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
3200
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
Low
Mammals - Short term dietary NOEL
(mg kg⁻¹)
- - -
(ppm diet)
- -
Birds - Acute LD₅₀ (mg kg⁻¹)
> 1500
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
Anas platyrhynchos
Moderate
Birds - Short term dietary (LC₅₀/LD₅₀)
- - -
Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
> 930
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
Lepomis macrochirus
Low
Fish - Chronic 21 day NOEC (mg l⁻¹)
- - -
Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
> 1100
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Daphnia magna
Low
Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)
260
P3 P = Other governments and regulators
3 = Unverified data of known source
Daphnia magna
Low
Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)
> 140.0
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
Americamysis bahia
Low
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)
0.0009
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
Lemna gibba
High
Non-target plants
- - -
- - -
Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)
95.0
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
Selenastrum capricornutum
Low
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)
> 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
Moderate
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)
3200
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
Low
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
2000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rabbit
-
Mammals - Inhalation LC₅₀ (mg l⁻¹)
6.9
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)
- - -
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
-
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
?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
;
E3 E = Unspecified genotoxicity type (miscellaneous data source)
3 = Negative
No data found
Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant
No data found
XNo, known not to cause a problem
No data found
Respiratory tract irritant Skin irritant Skin sensitiser
No data found
XNo, known not to cause a problem
No data found
Eye irritant Phototoxicant  
XNo, known not to cause a problem
No data found  
General human health issues
Moderately toxic
Possible liver toxicant
USEPA - possible human carcinogen
Handling issues
Property
Value and interpretation
General
No information available
CLP classification 2013
-
EC Risk Classification
Xn - Harmful: R22
EC Safety Classification
-
WHO Classification
III (Slightly hazardous)
UN Number
-
Waste disposal & packaging
-
TRANSLATIONS
Language
Name
English
pyrithiobac-sodium
French
-
German
-
Danish
-
Italian
-
Spanish
piritiobac sodico
Greek
-
Polish
pirytiobak sodowy
Swedish
-
Hungarian
-
Dutch
-

Record last updated: 27/11/2019
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