Dimethipin (Ref: N 252)

Dimethipin (Ref: N 252)	Last updated: 25/05/2025
(Also known as: UNI N252 ; oxidimethiin; oxydimethiin; tetrathiin)

SUMMARY

Dimethipin is a plant growth regulator and defoliant. It is highly soluble in water and has a low volatility. Depending on local conditions it may be persistent in both soil and water systems. It also has potential to leach to groundwater. Dimethipin is moderately toxic to aquatic species (except algae), birds, earthworms and honeybees. This substance also has a moderate oral mammalian toxicity, is an irritant and skin sensitizer. There is also the suggestion that it is a carcinogen.

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; GUS: High leachability; Drainflow: Very mobile	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Fish acute ecotoxicity: Moderate; Fish chronic ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Daphnia chronic ecotoxicity: Moderate; Bees acute contact ecotoxicity: Moderate; Bees acute oral ecotoxicity: Moderate; Earthworms acute ecotoxicity: Moderate; Earthworms chronic ecotoxicity: Moderate	Human health Moderate alert: Mammals acute toxicity: Moderate; Possible Carcinogen

GENERAL INFORMATION

Description

A plant growth regulator used on a range of crops

Example pests controlled

Growth - defoliant and desiccant

Example applications

Potatoes; Cotton; Rubber trees; Nursery stock

Efficacy & activity

Availability status

Current

Introduction & key dates

1974, 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 plant protection agent

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Not approved

Dossier rapporteur/co-rapporteur

Greece

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

C₆H₁₀O₄S₂

Canonical SMILES

CC1=C(S(=O)(=O)CCS1(=O)=O)C

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

PHVNLLCAQHGNKU-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C6H10O4S2/c1-5-6(2)12(9,10)4-3-11(5,7)8/h3-4H2,1-2H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
dimethipin	-

General status

Pesticide type

Herbicide; Plant Growth Regulator

Substance groups

Sulfone PGR

Minimum active substance purity

965 g kg⁻¹

Known relevant impurities

EU dossier - None declared

Substance origin

Synthetic

Mode of action

Interferes with protein synthesis in the plant epidermis, functions by stressing the plant’s stomatal system causing it to lose water and defoliate/desiccate.

CAS RN

55290-64-7

EC number

259-572-7

CIPAC number

689

US EPA chemical code

118901

PubChem CID

41385

CLP index number

No data found

Molecular mass

210.27

PIN (Preferred Identification Name)

5,6-dimethyl-2,3-dihydro-1γ6,4γ6-dithiine-1,1,4,4-tetrone

IUPAC name

2,3-dihydro-5,6-dimethyl-1,4-dithiine 1,1,4,4-tetraoxide

CAS name

2,3-dihydro-5,6-dimethyl-1,4-dithiin 1,1,4,4-tetraoxide

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

White crystalline solid

Formulations

Property

Value

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

UniRoyal

Example products using this active

Harvade 25F

Formulation and application details

Often available as a suspension concentrate that is diluted with water and used as a spray

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

1843

High

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

Heptane

3600

Xylene

10000

Methanol

122000

Acetone

Melting point (°C)

168

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

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

6.76 X 10^-01

Calculated

Log P

-0.17

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.59

Dissociation constant pKa) at 25 °C

10.9

Very weak acid

Vapour pressure at 20 °C (mPa)

0.051

Low volatility

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

2.33 X 10^-11

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

No maxima detected

Surface tension (mN m⁻¹)

68.7

at 20°C

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

183

Persistent

DT₅₀ (lab at 20 °C)

431

Very persistent

DT₅₀ (field)

183

Persistent

DT₉₀ (lab at 20 °C)

1025

Very persistent

DT₉₀ (field)

932

DT₅₀ modelling endpoint

Note

EU dossiers lab studies DT₅₀ range 157-673 days, DT₉₀ range 521-2236 days, field studies 2 soils DT₅₀ range 168-198 days USA, DT₉₀ range 658-1206 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

330

Stable

Note

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

Value

Stable

Note

Stable at pH 5 to pH 9 at 22 °C

Water-sediment DT₅₀ (days)

Water phase only DT₅₀ (days)

470

Stable

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)

Very mobile

K_oc (mL g⁻¹)

2.0

Notes and range

EU dossier K_oc range 1.0 (sand/loam) - 3.2 (clay) mL g⁻¹; Other sources: 10 mL g⁻¹ (DW3)

Freundlich

K_f (mL g⁻¹)

0.12

Very mobile

K_foc (mL g⁻¹)

4.6

¹/_n

1.02

Notes and range

2 USA/Canadian soils. K_f range 0.04-0.2, K_foc range 2.7-7.1, ¹/_n range1.02-1.03, Soils=2

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

7.55

Calculated

High leachability

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

Value

7.11 X 10⁰¹

Calculated

Note

Potential for particle bound transport index

Medium

Calculated

Potential for loss via drain flow

Very mobile

Calculated

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

Bio-concentration factor

BCF (l kg⁻¹)

4.3

Low potential

CT₅₀ (days)

Not available

Known soil and groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

cysteinyl-glycine

Rat (Urine)

N-acetyl-cysteinyl conjugates

Rat (Urine)

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

458

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)

Birds - Acute LD₅₀ (mg kg⁻¹)

896

Anas platyrhynchos

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

1173 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)

102

Eisenia foetida

Moderate

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

2.17

Eisenia foetida 56 day

Moderate

Soil micro-organisms

Nitrogen mineralisation: Chronic effect
Biopolymer degradation: Chronic effect

Dose: Not stated 63 Day

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

231

Folsomia candida

Non-target plants

Honeybees (Apis spp.)

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

100

Apis mellifera

Moderate

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

64.7

Apis mellifera

Moderate

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

> 937.5

Aphidius rhopalosiphi

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

600

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)

52.8

Oncorhynchus mykiss

Moderate

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

3.3

Oncorhynchus mykiss

Moderate

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

14.02

Danio rerio EC₅₀ Embryo

Moderate

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

29.9

Daphnia magna

Moderate

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

0.61

Daphnia magna

Moderate

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

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

11.8

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)

2.1

Lemna gibba

Moderate

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

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

Scenedesmus subspicatus

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)

458

Rat

Moderate

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

0.88

Rat (nose only)

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

No unacceptable risks to bystanders identified
Negligible risk of dietary exposure

Occupational

Risk of exposure acceptable under label recommendations for use for personal protection clothing and equipment

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=27.0 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

Eye irritant

Phototoxicant

No data found

General human health issues

US EPA - possible human carcinogen

Handling issues

Property

Value and interpretation

General

Not oxidising or explosive
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Health: H302

WHO Classification

II (Moderately hazardous)

UN Number

Not regulated

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

Chemically stable under standard ambient conditions

TRANSLATIONS

Language

Name

English

dimethipin

French

dimethipin

German

Dimethipin

Danish

dimethipin

Italian

dimetipin

Spanish

dimetipin

Greek

Polish

dimetypina

Swedish

Hungarian

dimethipin

Dutch

Norwegian

Record last updated:	25/05/2025
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