Pyrithiobac-sodium (Ref: DPX PE 350)

Pyrithiobac-sodium (Ref: DPX PE 350)	Last updated: 05/02/2024
(Also known as: KIH 2031)

SUMMARY

Pyrithiobac-sodium is a post-emergence herbicide. 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.

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
	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Bees acute contact ecotoxicity: Moderate	Human health Moderate alert: Possible Carcinogen Warning: Significant data are missing

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, registered USA

UK regulatory status

UK COPR regulatory status

Not approved

Date COPR inclusion expires

Not applicable

UK LERAP status

No UK approval for use

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Pending

Dossier rapporteur/co-rapporteur

Date EC 1107/2009 inclusion expires

Not applicable

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

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

Australia

Chemical structure

Isomerism

None

Chemical formula

C₁₃H₁₀ClN₂NaO₄S

Canonical SMILES

COC1=CC(=NC(=N1)SC2=C(C(=CC=C2)Cl)C(=O)[O-])OC.[Na+]

Isomeric SMILES

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 groups

Pyrimidinyloxybenzoic acid herbicide

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

602-931-3

CIPAC number

US EPA chemical code

078905

PubChem CID

23682187

CLP index number

No data found

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 Class (HRAC MoA class)

Herbicide Resistance Class (WSSA MoA class)

Insecticide Resistance Class (IRAC MoA class)

Not applicable

Fungicide Resistance Class (FRAC MOA class)

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

DuPont
Kumiai Chemical Industry Co. Ltd.

Example products using this active

Stap
Staple
Staple LX

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

High

Solubility - In organic solvents at 20 °C (mg l⁻¹)

812

Acetone

270000

Methanol

n-Hexane

205

Ethyl acetate

Melting point (°C)

234

Boiling point (°C)

Degradation point (°C)

234

Flashpoint (°C)

Octanol-water partition coefficient at pH 7, 20 °C

1.45 X 10^-01

Calculated

Log P

-0.84

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.61

Dissociation constant pKa) at 25 °C

2.34

Strong acid

Vapour pressure at 20 °C (mPa)

4.80 X 10^-06

Low volatility

Henry's law constant at 25 °C (Pa m³ mol⁻¹)

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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)

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 (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

Note

Aqueous photolysis DT₅₀ (days) at pH 7

Value

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

Note

Water-sediment DT₅₀ (days)

Water phase only DT₅₀ (days)

Air degradation

As this parameter is not normally measured directly, a surrogate measure is used: ‘Photochemical oxidative DT₅₀’. Where data is available, this can be found in the Fate Indices section below.

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d

0.5

K_oc

Notes and range

General literature data gives K_d values ranging from 0.32 (sandy loam) to 0.75 (silty loam). Peered review study - K_d 0.22 to 0.59 L/kg

Freundlich

K_f

K_foc

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

Photochemical oxidative DT₅₀ (hrs) as indicator of long-range air transport risk

Bio-concentration factor

BCF (l kg⁻¹)

Low risk

Based on LogP < 3

Low risk

CT₅₀ (days)

Known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

3200

Rat

Low

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)

> 1500

Anas platyrhynchos

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)

Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)

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)

> 25

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)

Chronic

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 bee species (1)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

Mode of exposure

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)

Beneficial insects (Ground beetles)

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Temperate Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

> 930

Lepomis macrochirus

Low

Temperate Freshwater Fish - Chronic 21 day NOEC (mg l⁻¹)

Tropical Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

Temperate Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

> 1100

Daphnia magna

Low

Temperate Freshwater Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)

260

Daphnia magna

Low

Tropical Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)

> 140.0

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

Lemna gibba

High

Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)

95.0

Selenastrum capricornutum

Low

Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)

Mesocosm study data

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

Rat

Low

Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)

2000

Rabbit

Mammals - Inhalation LC₅₀ (mg l⁻¹)

6.9

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)

Mammalian dose elimination route and rate

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

No data found

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

No data found

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

Moderately toxic
Possible liver toxicant
US EPA - possible human carcinogen; CLP data - suspected carcinogen

Handling issues

Property

Value and interpretation

General

No information available

CLP classification 2013

Health: H319, H351, H373
Environment: H400, H410

WHO Classification

III (Slightly hazardous)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

pyrithiobac-sodium

French

German

Danish

Italian

Spanish

piritiobac sodico

Greek

Polish

pirytiobak sodowy

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	05/02/2024
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