Etridiazole (Ref: Olin 2424)

Etridiazole (Ref: Olin 2424)	Last updated: 22/05/2025
(Also known as: echlomezol; ethazol; athazole; terrazole; OM 2424)

SUMMARY

Etridazole is a fungicide used to control soil-borne infections. It is moderately soluble in water and miscible with many organic solvents. It is considered to be a volatile substance; not normally persistent in soil systems but may be more persistent in water depending upon local conditions. There is a low risk of the substance leaching to groundwater. Etridazole is moderately toxic to most aquatic organisms but data for terrestrial species is missing. It is moderately toxic to humans via the oral route and there are concerns regarding the chronic toxicity of etridazole particularly with respect to reproduction/developmental effects and the possibility it is an endocrine disrupter.

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 Moderate alert: Drainflow: Slightly mobile	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Fish acute ecotoxicity: Moderate; Fish chronic ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Daphnia chronic ecotoxicity: Moderate	Human health High alert: Endocrine disrupter; Reproduction/development effects

GENERAL INFORMATION

Description

A fungicide for soil or compost incorporation to control mainly Phytophthora and Pythium spp.

Example pests controlled

Phytophthora & Pythium spp.; Damping off; Powdery mildew

Example applications

Field crops; Vegetables; Ornamentals; Lawns; Tomato and other vegetable seedlings

Efficacy & activity

Availability status

Current

Introduction & key dates

circa 1972, introduced

GB regulatory status

GB COPR regulatory status

Not approved

Date COPR inclusion expires

Withdrawn

GB LERAP status

No data

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Not approved

Dossier rapporteur/co-rapporteur

Netherlands/Spain

Date EC 1107/2009 inclusion expires

Expired

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; USA

Chemical structure

Isomerism

None

Chemical formula

C₅H₅Cl₃N₂OS

Canonical SMILES

CCOC1=NC(=NS1)C(Cl)(Cl)Cl

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

KQTVWCSONPJJPE-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C5H5Cl3N2OS/c1-2-11-4-9-3(10-12-4)5(6,7)8/h2H2,1H3

2D structure diagram/image available?

Yes

General status

Pesticide type

Fungicide

Substance groups

Thiadiazole fungicide

Minimum active substance purity

970 g kg⁻¹

Known relevant impurities

EU dossier - none declared

Substance origin

Synthetic

Mode of action

Contact with protective and curative action. Lipid peroxidation inhibitor.

CAS RN

2593-15-9

EC number

219-991-8

CIPAC number

518

US EPA chemical code

084701

PubChem CID

17432

CLP index number

613-133-00-X

Molecular mass

247.53

PIN (Preferred Identification Name)

5-ethoxy-3-(trichloromethyl)-1,2,4-thiadiazole

IUPAC name

ethyl 3-trichloromethyl-1,2,4-thiadiazol-5-yl ether

CAS name

5-ethoxy-3-(trichloromethyl)-1,2,4-thiadiazole

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

Clear colourless to reddish brown semi-solid

Formulations

Property

Value

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

AgriGuard
Standon
Scotts
Ollin
Mallinckrodt

Example products using this active

Terraguard
Aaterra
Pansoil
Truban
Dwell

Formulation and application details

Often supplied as a wettable powder, emulsifiable concentrate or dust

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

88.9

Moderate

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

Miscible

Xylene

Miscible

Ethanol

Miscible

Methanol

Miscible

Hexane

Melting point (°C)

Boiling point (°C)

113

Degradation point (°C)

Flashpoint (°C)

111

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

2.34 X 10⁰³

Calculated

Log P

3.37

High

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.497

Dissociation constant pKa) at 25 °C

2.77

Very weak base

Vapour pressure at 20 °C (mPa)

1430

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)

3.02

Moderately volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

Maxima 220nm = 5444

Surface tension (mN m⁻¹)

71.9

at 22°C

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

Non-persistent

DT₅₀ (lab at 20 °C)

8.98

Non-persistent

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

72.5

Moderately persistent

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU dossier lab studies range 2.22 (loam) - 45.5 (sandy loam) days, DT₉₀ range 7.4-194 days

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

0.04

Fast

Note

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

Value

Moderately persistent

Note

Slightly sensitive to pH: DT₅₀ 92 days at pH 5, 88 days at pH 9 all at 25 °C

Water-sediment DT₅₀ (days)

1.85

Fast

Water phase only DT₅₀ (days)

1.31

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)

Slightly mobile

K_oc (mL g⁻¹)

1000

Notes and range

Freundlich

K_f (mL g⁻¹)

7.17

Moderately mobile

K_foc (mL g⁻¹)

289

¹/_n

0.873

Notes and range

EU dossier K_f range 5.06-8.24 mL g⁻¹, K_foc range 195-349 mL g⁻¹, ¹/_n range 0.84-0.92, Soils=3

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.47

Calculated

Low leachability

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

Value

1.86 X 10^-02

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Slightly mobile

Calculated

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

18.67

Calculated using the Atkinson method. Assumed 1.56E+06 OH/cm³, 12 hr

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

165

Threshold for concern

CT₅₀ (days)

Known soil metabolites

Metabolite

Major/Minor fraction

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

Estimated maximum occurrence fraction

Notes

dichloroetridiazole

Major fraction

0.133

etridiazole acid

Major fraction

0.310

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)

dichloroetridiazole

Relevancy unknown

etridiazole acid

Relevancy unknown

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

5-hydroxymethyl etridiazole

Rat

5-hydroxyethoxy etridiazole acid

Rat

N-carbethoxy oxamic acid

Rat (Urine)

ethyl (aminocarbamyl) carbamate

Rat (Urine)

oxalic acid

Rat (Urine)

etridiazole carboxylic acid

Rat (Urine)

3-hydroxymethyl etridiazole

Rat

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 945

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

2.7

Rat

High

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

560

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

286 mg kg bw⁻¹ day⁻¹

Anas platyrhynchos

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

Nitrogen mineralisation: Chronic effect
Carbon mineralisation: Chronic effect

Dose: Not stated

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)

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

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

1494

Aphidius rhopalosiphi

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

5003

Typhlodromus pyri

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)

2.4

Oncorhynchus mykiss

Moderate

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

0.12

Oncorhynchus mykiss

Moderate

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

1.06

Danio rerio EC₅₀ Embryo

Moderate

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

3.1

Daphnia magna

Moderate

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

0.37

Daphnia magna

Moderate

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

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

2.5

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

7.3

Lemna gibba

Moderate

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

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

0.3

Pseudokirchneriella subcapitata

Moderate

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

0.32

Unknown species

Moderate

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)

> 945

Rat

Moderate

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

5000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 5.7

Rat (nose only)

Other Mammal toxicity endpoints

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

0.015

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

0.15

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

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

0.03

Dermal penetration studies (%)

18-30

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

Bystanders should be prohibited from entering glasshouses post-application

Occupational

PPE/PPC required to minimise exposure

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=15.0 µg l⁻¹

Mammalian dose elimination route and rate

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

Respiratory tract irritant

Skin irritant

Skin sensitiser

Eye irritant

Phototoxicant

No data found

General human health issues

Possible liver toxicant
CLP data - suspected carcinogen; US EPA - probable human carcinogen

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
IMDG Transport Hazard Class 9

CLP classification 2013

Health: H302, H317, H351
Environment: H400, H410

WHO Classification

III (Slightly hazardous)

UN Number

UN3082

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

etridiazole

French

etridiazole

German

Etridiazol

Danish

etridiazole

Italian

etridiazolo

Spanish

etridiazol

Greek

Polish

etridiazol

Swedish

Hungarian

Dutch

etridiazool

Norwegian

Record last updated:	22/05/2025
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