Oxadiazon (Ref: RP 17623 )

Oxadiazon (Ref: RP 17623 )	Last updated: 22/08/2024
(Also known as: oxydiazon; oxadiazo)

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 High alert: Persistent; Potential for particle bound transport: High	Ecotoxicity High alert: Fish chronic ecotoxicity: High	Human health High alert: Reproduction/development effects

GENERAL INFORMATION

Description

A pre-emergence or early post-emergence herbicide used to control bindweed and some annual broad-leaved weeds in food and non-food situations

Example pests controlled

Crabgrass; Annual bluegrass; Goosegrass; Buttonweed; Annual sedge

Example applications

Turf, sports greens & ornamental grass; Non-cropped areas including playgrounds, roadsides; cemeteries; Ornamental shrubs, Vines; Trees

Efficacy & activity

Availability status

Current

Introduction & key dates

1969, first reported

GB regulatory status

GB COPR regulatory status

Not approved

Date COPR inclusion expires

Expired

GB LERAP status

No UK approval for use as a pesticide

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Not approved

Dossier rapporteur/co-rapporteur

Italy/Spain

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
				✓

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, USA

Chemical structure

Isomerism

None

Chemical formula

C₁₅H₁₈Cl₂N₂O₃

Canonical SMILES

CC(C)OC1=C(C=C(C(=C1)N2C(=O)OC(=N2)C(C)(C)C)Cl)Cl

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

CHNUNORXWHYHNE-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C15H18Cl2N2O3/c1-8(2)21-12-7-11(9(16)6-10(12)17)19-14(20)22-13(18-19)15(3,4)5/h6-8H,1-5H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
oxadiazon	-

General status

Pesticide type

Herbicide

Substance groups

Oxadiazolone herbicide

Minimum active substance purity

Known relevant impurities

EU dossier - None declared

Substance origin

Synthetic

Mode of action

Selective with contact action. Inhibits protoporphyrinogen oxidase, leading to irreversible cell membrane damage.

CAS RN

19666-30-9

EC number

243-215-7

CIPAC number

213

US EPA chemical code

109001

PubChem CID

29732

CLP index number

606-045-00-8

Molecular mass

345.2

PIN (Preferred Identification Name)

IUPAC name

5-tert-butyl-3-(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2(3H)-one

CAS name

3-(2,4-dichloro-5-(1-methylethoxy)phenyl)-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2(3H)-one

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

Physical state

Colourless crystals

Formulations

Property

Value

Example manufacturers & suppliers of products using this active now or historically

Bayer
Certis
Clayton
Standon
Rhone Poulenc

Example products using this active

Ronstar 2G
Ronstar Liquid
Standon Roxx L

Formulation and application details

Often supplied as an emulsifiable concentrate or as dry granules that are mixed with compost

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

0.57

Low

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

350000

Acetone

1000000

Benzene

350000

Toluene

122400

Methanol

Melting point (°C)

88.5

Boiling point (°C)

282.1

Degradation point (°C)

Flashpoint (°C)

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

2.14 X 10⁰⁵

Calculated

Log P

5.33

High

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

0.67

Low volatility. If applied directly to plants, drift is a concern & mitigation is advisable

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

3.80 X 10^-02

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

5.1

24 hr

Volatilisation is not considered critical for air pollution

From soil surface

6.7

24 hr

Volatilisation is not considered critical for air pollution

Maximum UV-vis absorption L mol⁻¹ cm⁻¹

Neutral solution: 208.5nm = 35843, 292nm = 3283
Acidic solution: 208.5nm = 34776, 292.5nm = 3216
Basic solution: 218nm = 20718, 293nm = 4286

Surface tension (mN m⁻¹)

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

502

Very persistent

DT₅₀ (lab at 20 °C)

502

Very persistent

DT₅₀ (field)

165

Persistent

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

545

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 118-825 days, field studies DT₅₀ range 90-330 days, DT₉₀ range 298-1085 days; Other sources: DT₅₀ 60 days (DW4)

Dissipation rate RL₅₀ (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

4.3

Note

Grape berries, n=1

Aqueous photolysis DT₅₀ (days) at pH 7

Value

5.9

Moderately fast

Note

DT₅₀ 26.3 hrs at pH 9 sterile water - equivalent to 5.9 days at 40 deg N, 2.2 days sterile pond water

Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7

Value

Moderately persistent

Note

Stable pH 4 to pH 7, at 25 °C for 31 days, DT₅₀ 11.7 days at pH 9, 20 °C

Water-sediment DT₅₀ (days)

126.5

Slow

Water phase only DT₅₀ (days)

17.9

Slow

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.

Decay in stored produce DT₅₀

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d (mL g⁻¹)

Slightly mobile

K_oc (mL g⁻¹)

3200

Notes and range

Freundlich

K_f (mL g⁻¹)

35.9

Slightly mobile

K_foc (mL g⁻¹)

1294

¹/_n

0.905

Notes and range

EU dossier K_f range 12.73-62.15 mL g⁻¹, foc range 979-1527 mL g⁻¹, ¹/_n range 0.855-0.958; Other studies: Mean of 3 soils. Ando soil OC=5.2% K_f=150; Gray lowland soil OC=1.4% K_f=120; Light Ando soil OC=1.1% kf=100.

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.97

Calculated

Transition state

SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate

Value

7.97 X 10^-02

Calculated

Note

Potential for particle bound transport index

High

Calculated

Potential for loss via drain flow

Slightly mobile

Calculated

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

0.22

Calculated using the Atkinson method. Assumed 1.5E+06 OH/cm³, 12 hr

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

243

Threshold for concern

CT₅₀ (days)

2.5

Known soil metabolites

Metabolite

Major/Minor fraction

$Click here for further information on Major/Minor fraction$

Estimated maximum occurrence fraction

Notes

N'-[2,4-dichloro-5-(propan-2-N'-[2,4-dichloro-5-(propan-2-dimethylpropanehydrazide (Ref: AE 0608022)

Minor fraction

Anaerobic

Known groundwater metabolites

Metabolite

EC SANCO/221/2000 relevancy

ADI (mg kg⁻¹ bodyweight day⁻¹)

WHO drinking water guidance value (μg L⁻¹ day⁻¹)

N'-[2,4-dichloro-5-(propan-2-N'-[2,4-dichloro-5-(propan-2-dimethylpropanehydrazide (Ref: AE 0608022)

Relevancy unknown

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

N'-[2,4-dichloro-5-(propan-2-N'-[2,4-dichloro-5-(propan-2-dimethylpropanehydrazide (Ref: AE 0608022)

Water; Sediment

2,4-dichloro-1-(propan-2-yloxy)benzene (Ref: AE 0592465)

2,4-dichlorophenyl propan-2-yl ether

Water; Sediment

5-tert-butyl-3-(2,4-dichloro-5-hydroxyphenyl)-1,3,4-oxadiazol-2(3H)-one (Ref: AE 0608021)

Water; Plant

Ref: AE 0608035

Water (Photolysis)

5-tert-butyl-3-(2,4-dichloro-5-methoxyphenyl)-1,3,4-oxadiazol-2(3H)-one (Ref: AE 0618784)

Plant

2-{4-[2,4-dichloro-5-(propan-2-yloxy)phenyl]-5-oxo-4,5-dihydro-1,3,4-oxadiazol-2-yl}-2-methylpropanoic acid (Ref: AE 0616182)

Plant

2,2-dimethyl-N-(6-methyl-2-oxo-6,7-dihydrofuro[3',2':4,5]benzo[1,2-d]oxazol-3-yl)propionamide (Ref: AE 1117150)

Water (Photolysis)

N-[6-chloro-2-oxo-5-(propan-2-yloxy)-1,3-benzoxazol-3(2H)-yl]-2,2-dimethylpropanamide (Ref: AE 0608033)

Water (Photolysis)

Ref: AE 1117815

Water (Photolysis)

3-[2,4-dichloro-5-(propan-2-yloxy)phenyl]-5-(1-hydroxy-2-methylpropan-2-yl)-1,3,4-oxadiazol-2(3H)-one (Ref: AE 0618785)

Plant

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 5000

Rat

Low

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Rat 2 yr

(ppm diet)

Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)

Birds - Acute LD₅₀ (mg kg⁻¹)

> 2150

Colinus virginianus

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

> 5000 mg kg feed⁻¹

Anas platyrhynchos

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

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

> 500

Eisenia foetida corr

Moderate

Earthworms - Chronic NOEC, reproduction (mg kg⁻¹)

66.5

Eisenia foetida corr

Moderate

Soil micro-organisms

Nitrogen mineralisation: No significant adverse effect
Carbon mineralisation: No significant adverse effectffect

Dose: 6 L product ha⁻¹

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Non-target plants

20.2

Tomato
Vegetative vigour ER₅₀
as g ha⁻¹

39.23

Cucumber
Seedling emergence, ER₅₀
as g ha⁻¹

Honeybees (Apis spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

> 100

Apis mellifera

Low

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

> 110.5

Apis mellifera

Low

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) as % Mortality at dose 30 g ha⁻¹

Chrysoperla carnea Larva

Beneficial insects (Parasitic wasps) as Mortality LR₅₀ g ha⁻¹

875

Aphidius rhopalosiphi

Beneficial insects (Predatory mites) as Mortality LR₅₀ g ha⁻¹

149

Typhlodromus pyri

Beneficial insects (Ground beetles) as % Mortality at dose 750 g ha⁻¹

Poecilus cupreus

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

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

1.2

Oncorhynchus mykiss

Moderate

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

0.00088

Oncorhynchus mykiss

High

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

1.77

Danio rerio EC₅₀ Embryo

Moderate

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

> 2.4

Daphnia magna

Moderate

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

0.03

Daphnia magna

Moderate

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

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

0.23

Americamysis bahia

Moderate

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)

0.057

Lemna gibba

Moderate

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

0.004

Scenedesmus subspicatus

High

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

Mesocosm study data

NOEAEC mg l⁻¹

Marine bivalves

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)

> 5000

Rat

Low

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 2.77

Rat (aerosol)

Other Mammal toxicity endpoints

ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)

0.0036

Rat SF=100

ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)

0.12

Rat SF=100

AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)

AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)

0.05

Rat SF=100

Dermal penetration studies (%)

2-3

Dangerous Substances Directive 76/464

Exposure Routes

Public

Negligible risk to bystanders

Occupational

Use of PPE/PPC recommended

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

0.1

EU Dir 89/778/EC limit; Calc MAC=11 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

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

Possible liver toxicant
May cause anaemia
US EPA - possible human carcinogen

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
IMDG Transport Hazard Class 9
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Environment: H400, H410

WHO Classification

U (Unlikely to present an acute hazard)

UN Number

UN3077

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

Stability may be affected my light

TRANSLATIONS

Language

Name

English

oxadiazon

French

oxadiazon

German

Oxadiazon

Danish

oxadiazon

Italian

oxadiazon

Spanish

oxadiazon

Greek

Polish

oksadiazon

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	22/08/2024
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