Chlorthal-dimethyl (Ref: DAC 893)

Chlorthal-dimethyl (Ref: DAC 893)	Last updated: 22/08/2024
(Also known as: dimethyl tetrachloroterephthalate; DCPA; dacthal)

SUMMARY

Chlorthal-dimethyl is a selective benzoic acid herbicide. It has a low aqueous solubility and a low to moderate volatility. It is considered to be moderately persistent in soil systems but can be stable in aquatic systems depending upon conditions. Based on its physico-chemical properties it is not expected to leach to groundwater. Its toxicity to fauna and flora is low to medium. It also has a low mammalian toxicity and no evidence has been found that suggests it will cause serious adverse health effects unless exposure is high.

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: Potential for particle bound transport: High	Ecotoxicity Moderate alert: Fish acute ecotoxicity: Moderate; Fish chronic ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Daphnia chronic ecotoxicity: Moderate; Earthworms acute ecotoxicity: Moderate	Human health Moderate alert: Possible Carcinogen; Genotoxic; Reproduction/development effects

GENERAL INFORMATION

Description

A residual benzoic acid herbicide for pre-emergence control of annual grasses and some annual broad-leaved weeds

Example pests controlled

Barnyardgrass; Bindweed; Nightshade; Chickweed; Crabgrass; Fat-hen; Pigweed; Redshank; Fescue; Stinging nettle; Petty spurge; Ryegrass

Example applications

Vegetables including brassicas, peas & beans, onions, carrots, turnips; Strawberries; Cotton; Lucerne; Ornamentals; Lawns

Efficacy & activity

Availability status

Current

Introduction & key dates

1958, first registered USA (now banned)

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

Greece

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

Chemical structure

Isomerism

None

Chemical formula

C₈H₆Cl₄O₄

Canonical SMILES

COC(=O)C1=C(C(=C(C(=C1Cl)Cl)C(=O)OC)Cl)Cl

Isomeric SMILES

International Chemical Identifier key (InChIKey)

NPOJQCVWMSKXDN-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C10H6Cl4O4/c1-17-9(15)3-5(11)7(13)4(10(16)18-2)8(14)6(3)12/h1-2H3

2D structure diagram/image available?

Yes

General status

Pesticide type

Herbicide

Substance groups

Benzenedicarboxylic acid herbicide; Phthalic acid herbicide

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Selective, non-systemic, acts by inhibiting seed germination. Microtubule assembly inhibition.

CAS RN

1861-32-1

EC number

217-464-7

CIPAC number

328

US EPA chemical code

078701

PubChem CID

2943

CLP index number

No data found

Molecular mass

331.96

PIN (Preferred Identification Name)

dimethyl 2,3,5,6-tetrachlorobenzene-1,4-dicarboxylate

IUPAC name

dimethyl tetrachloroterephthalate

CAS name

dimethyl 2,3,5,6-tetrachloro-1,4-benzenedicarboxylate

Other status information

Chemical subject to PIC regulations; PAN Bad Actor Chemical

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 to grey crystalline powder

Related substances & organisms

chlorthal

chlorthal-monomethyl

Formulations

Property

Value

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

Certis
Diamond Shamrock

Example products using this active

Dacthal
Decimate

Formulation and application details

Usually supplied as a wettable powder or granular formulation

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

0.21

Low

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

250000

Benzene

170000

Toluene

140000

Xylene

100000

Acetone

Melting point (°C)

156

Boiling point (°C)

345

Degradation point (°C)

360

Flashpoint (°C)

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

1.91 X 10⁰⁴

Calculated

Log P

4.28

High

Fat solubility of residues

Solubility

Soluble

Data type

Regulatory data based on LogP

Density (g ml⁻¹)

1.56

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

0.21

at 25 °C

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)

0.3486

Moderately volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

212.4nm = 48000, 296.6nm = 1240, 290nm = 1030, 295nm = 1210, 304nm = 659, 314nm = 93.1

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)

Moderately persistent

DT₅₀ (field)

Moderately persistent

DT₉₀ (lab at 20 °C)

Moderately persistent

DT₉₀ (field)

156

DT₅₀ modelling endpoint

Note

EU dossier Lab studies DT₅₀ range 25-97 days, DT₉₀ range 65-166 days, Field studies DT₅₀ range 6-98 days, DT₉₀ range 20-328 days; Other sources: DT₅₀ 33.8 days (R4); 11-105 days (R4)

Dissipation rate RL₅₀ (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

37.8

Note

Kentucky bluegrass thatch, n=1

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Stable

Note

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

Value

Stable

Note

Water-sediment DT₅₀ (days)

Moderately fast

Water phase only DT₅₀ (days)

130

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)

37.0

Slightly mobile

K_oc (mL g⁻¹)

2963

Notes and range

EU dossier K_d range 6.80-59.5 mL g⁻¹, K_oc range 1500-4444 mL g⁻¹, Soils=8

Freundlich

K_f (mL g⁻¹)

30.5

Slightly mobile

K_foc (mL g⁻¹)

2683

¹/_n

0.947

Notes and range

EU dossier K_f range 6.67-70.3 mL g⁻¹, K_foc range 1778-4375 mL g⁻¹, ¹/_n range 0.912-0.985, Soils=8

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

0.96

Calculated

Low leachability

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

Value

1.88 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

580.8

Calculated using the Atkinson method

Substance of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

2574

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

monomethyl-tetrachloroterephthalic acid

Major fraction

0.113

chlorthal

Major fraction

0.944

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)

monomethyl-tetrachloroterephthalic acid

Relevant

Other known metabolites

None

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

High

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

> 2250

Colinus virginianus

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

> 1637 mg kg bw⁻¹ day⁻¹

Colinus virginianus

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)

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

485

Aphidius rhopalosiphi

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

> 40000

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)

> 4.7

Oncorhynchus mykiss

Moderate

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

0.056

Oncorhynchus mykiss

Moderate

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

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

> 4.6

Daphnia magna

Moderate

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

0.246

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)

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

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

> 11

Lemna gibba

Low

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

> 10

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)

> 5000

Rat

Low

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 4.48

Rat

Other Mammal toxicity endpoints

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

0.01

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

0.5

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

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

None allocated

Dermal penetration studies (%)

6-8

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

Negligible risk to the public

Occupational

Acceptable risk with PPE/PPC

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

Possible liver, thyroid & lung toxicant
US EPA - possible human carcinogen

Handling issues

Property

Value and interpretation

General

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

CLP classification 2013

Environment: H400, H410

WHO Classification

III (Slightly hazardous)

UN Number

UN3077

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

chlorthal-dimethyl

French

chlorthal-dimethyle

German

Chlorthal-dimethyl

Danish

chlorthal-dimethyl

Italian

clortal-dimetile

Spanish

clortal-dimetil

Greek

Polish

chlortal dimetylowy

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