Hymexazol (Ref: F 319)

Hymexazol (Ref: F 319)	Last updated: 09/04/2025
(Also known as: hydroxyisoxazole; SF 6505)

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: Drainflow: Mobile	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Birds chronic ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Daphnia chronic ecotoxicity: Moderate; Earthworms acute ecotoxicity: Moderate	Human health High alert: Reproduction/development effects

GENERAL INFORMATION

Description

A systemic fungicide used to control soil-borne diseases caused by Fusaruim, Aphanomyces and Pythium spp.

Example pests controlled

Fusarium crown rot; Root rot; Stem rot

Example applications

Rice; Sugarbeet; Fodder beet; Vegetables; Tomatoes; Ornamentals

Efficacy & activity

Availability status

Current

Introduction & key dates

1966, first reported; 1969, Introduced Japan

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

31/05/2031

GB LERAP status

None

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Austria/Sweden

Date EC 1107/2009 inclusion expires

31/08/2026

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

Morocco

Chemical structure

Isomerism

None

Chemical formula

C₄H₅NO₂

Canonical SMILES

CC1=CC(=O)NO1

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

KGVPNLBXJKTABS-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C4H5NO2/c1-3-2-4(6)5-7-3/h2H,1H3,(H,5,6)

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
hymexazol	-

General status

Pesticide type

Fungicide

Substance groups

Oxazole fungicide

Minimum active substance purity

985 g kg⁻¹

Known relevant impurities

EU dossier - None declared

Substance origin

Synthetic

Mode of action

Systemic, inhibits fungal growth by inhibiting nucleic acid synthesis (DNA / RNA synthesis).

CAS RN

10004-44-1

EC number

233-000-6

CIPAC number

528

US EPA chemical code

PubChem CID

24781

CLP index number

613-115-00-1

Molecular mass

99.15

PIN (Preferred Identification Name)

IUPAC name

5-methylisoxazol-3-ol

CAS name

5-methyl-3(2H)-isoxazolone

Other status information

Relevant Environmental Water Quality Standards

Herbicide Resistance Class (HRAC MoA class)

Not applicable

Herbicide Resistance Class (WSSA MoA class)

Not applicable

Insecticide Resistance Class (IRAC MoA class)

Not applicable

Fungicide Resistance Class (FRAC MOA class)

Examples of recorded resistance

Physical state

Colourless to pale yellow coloured crystals

Formulations

Property

Value

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

Bayer CropScience
Summit Agro
AgroCare
Sanko

Example products using this active

Tachigaren WP
Terrazol
Hymexate
Sound

Formulation and application details

Often supplied as a wettable powder, dusts , emulsifiable concentrates and seed treatments

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

65100

High

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

730000

Acetone

200000

Benzene

12200

Hexane

968000

Methanol

Melting point (°C)

83.9

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

180

Flashpoint (°C)

203

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

2.00 X 10⁰⁰

Calculated

Log P

0.3

Low

Fat solubility of residues

Solubility

Insoluble

Data type

Regulatory data based on LogP

Density (g ml⁻¹)

0.55

Dissociation constant pKa) at 25 °C

5.92

Weak acid

Vapour pressure at 20 °C (mPa)

182

Highly volatile. If applied directly to plants or soil, drift is a concern & mitigation is advisable

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

2.77 X 10^-04

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

24 hr

From soil surface

7.4

24 hr

Volatilisation is not considered critical for air pollution

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

Neutral solution: 205.6nm = 6796.4
Acidic solution: 201.9nm = 10344
Basic solution: 212.9nm = 5077

Surface tension (mN m⁻¹)

72.1

at 20°C

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)

17.8

Non-persistent

DT₅₀ (field)

6.8

Non-persistent

DT₉₀ (lab at 20 °C)

Moderately persistent

DT₉₀ (field)

22.7

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 13.7-32 days, DT₉₀ range 45-105 days; Field studies (DAR) DT₅₀ range 3.5-26 days; DT₉₀ range 12-87 days

Dissipation rate RL₅₀ (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

3.1

Note

Published literature RL₅₀ range 2.9-3.3 days, 3 field crops, various matrices, n=8

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Stable

Note

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

Value

Stable

Note

Stable pH 5 to 9 at 20 °C

Water-sediment DT₅₀ (days)

5.9

Fast

Water phase only DT₅₀ (days)

5.8

Moderately fast

Sediment 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.

Decay in stored produce DT₅₀

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d (mL g⁻¹)

K_oc (mL g⁻¹)

Notes and range

Freundlich

K_f (mL g⁻¹)

1.14

Mobile

K_foc (mL g⁻¹)

56.5

¹/_n

0.816

Notes and range

EU dossier K_f range 0.15-3.09, K_foc range 12-124 mL g⁻¹, ¹/_n range 0.74-0.93, Soils=5

pH sensitivity

Yes. Adsorption weaker on alkalaine soils.

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.87

Calculated

Transition state

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

Value

1.13 X 10^-02

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Mobile

Calculated

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

0.6

Calculated using the Atkinson method

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

0.49

Estimated

Low potential

CT₅₀ (days)

Not available

Known soil metabolites

Metabolite

Major/Minor fraction

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

Estimated maximum occurrence fraction

Notes

acetoacetimide

Minor fraction

Anaerobic

crotonic acid

Minor fraction

Anaerobic

Known groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

5-methyl-2(3H)-oxazolone (Ref: RMH-1915)

Water

0.172

hymexanil-O-glucoside

Plant

hymexazol-O-diglucoside

Plant

hymexazol-N-monoglucoside

Plant

acetoacetic acid

Water

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

1600

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Rat 2 yr

High

(ppm diet)

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

Rat Reproductive NOEL

Moderate

Birds - Acute LD₅₀ (mg kg⁻¹)

> 1085

Coturnix japonica

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

> 5200 mg kg feed⁻¹

Coturnix japonica

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

86.5

Colinus virginianus NOEL

Moderate

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

281.9

Eisenia foetida

Moderate

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)

> 100

Apis mellifera

Low

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

> 100

Apis mellifera

Low

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

Chronic

Notes

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) as Mortality LR₅₀ g ha⁻¹

1426

Aphidius rhopalosiphi

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

1107

Typhlodromus pyri

Beneficial insects (Ground beetles)

0% Mortality at dose 0.208 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)

> 100

Oncorhynchus mykiss

Low

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

> 100

Oncorhynchus mykiss

Low

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

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

Daphnia magna

Moderate

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

0.8

Daphnia magna

Moderate

Tropical Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (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)

1.6

Chironomus riparius

Moderate

Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)

Aquatic plants (free-floating, growth) - Acute 7 day EC₅₀, biomass (mg l⁻¹)

8.8

Lemna gibba

Moderate

Aquatic plants (rooted, growth) - Acute 14 day EC₅₀, biomass (mg l⁻¹)

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

Pseudokirchneriella subcapitata 5 day

Low

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)

1600

Rat

Moderate

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

2000

Rabbit

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 0.65

Rat 4 hr

Other Mammal toxicity endpoints

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

0.17

Rat SF=100

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

0.5

Rabbit 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)

0.17

Dog SF=100

Dermal penetration studies (%)

100

default

Dangerous Substances Directive 76/464

Exposure Routes

Public

Occupational

PPE/PPC advised

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

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

Highly toxic
Risk of serious damage to eyes
Liver, thyroid and kidney toxicant

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising

CLP classification 2013

Health: H302, H318
Environment: H412

WHO Classification

III (Slightly hazardous)

UN Number

Not regulated

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

Chemically stable under standard ambient conditions

TRANSLATIONS

Language

Name

English

hymexazol

French

hymexazol

German

Hymexazol

Danish

hymexazol

Italian

hymexazol

Spanish

hymexazol

Greek

Polish

hymeksazol

Swedish

hymexazol

Hungarian

himexazol

Dutch

Norwegian

Record last updated:	09/04/2025
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