Chlorthal-dimethyl (Ref: DAC 893)

Chlorthal-dimethyl (Ref: DAC 893)	Last updated: 23/12/2020
(Also known as: dimethyl tetrachloroterephthalate; DCPA; dacthal)

GENERAL INFORMATION

Description

A residual benzoic acid herbicide for pre-emergent 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

circa 1960

UK regulatory status

UK COPR regulatory status

Not approved

Date COPR inclusion expires

Expired

UK LERAP status

None

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

Also used in

Australia

Chemical structure

Isomerism

Chemical formula

C₈H₆Cl₄O₄

Canonical SMILES

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

Isomeric SMILES

No data

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 group

Benzenedicarboxylic acid

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

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

Relevant Environmental Water Quality Standards

Herbicide Resistance Classification (HRAC)

Herbicide Resistance Classification (WSSA)

Insecticide Resistance Classification (IRAC)

Not applicable

Fungicide Resistance Classification (FRAC)

Not applicable

Examples of recorded resistance

Physical state

Colourless to grey crystalline powder

Related substances & organisms

propachlor

Formulations

Property

Value

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

Dacthal
Decimate

Example products using this active

Certis
Diamond Shamrock

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)

Not expected to self ignite; Not highly flammable

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

1.91 X 10⁰⁴

Calculated

Log P

4.28

High

Bulk density (g ml⁻¹)

1.56

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

0.21

Low volatility

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

0.3486

Moderately volatile

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 on plant matrix

Value

Note

Dissipation rate RL₅₀ 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

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d

37.0

Slightly mobile

K_oc

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

30.5

Slightly mobile

K_foc

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

Key metabolites

Metabolite

Formation medium

Estimated maximum occurrence fraction

1107/2009 relevancy

2,3,5,6-tetrachloroterephthalic acid

Soil

0.944

Relevant, Major fraction

monomethyl-tetrachloroterephthalic acid

Soil

0.113

Relevant, Major fraction

ECOTOXICOLOGY

Property

Value

Source; quality score; and other information

Interpretation

Bio-concentration factor

BCF (l kg⁻¹)

2574

Threshold for concern

CT₅₀ (days)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 5000

Rat

Low

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Rat 2 year

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/day

Colinus virginianus

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

Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

> 4.7

Oncorhynchus mykiss

Moderate

Fish - Chronic 21 day NOEC (mg l⁻¹)

0.056

Oncorhynchus mykiss

Moderate

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

> 4.6

Daphnia magna

Moderate

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

0.246

Daphnia magna

Moderate

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

Non-target plants

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

> 10

Scenedemus subspicatus

Low

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

Honeybees (Apis spp.)

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

> 100

Low

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

> 100

Low

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

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 pollinators (1)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

Mode of exposure

Other pollinators (2)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

Mode of exposure

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

> 500

Eisenia foetida corr

Moderate

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

Other soil macro-organisms

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Other arthropod (1)

LR₅₀ g ha⁻¹

485

Aphidius rhopalosiphi

% Effect

Other arthropod (2)

LR₅₀ g ha⁻¹

40000

>
Typhlodromus pyri

% Effect

Soil micro-organisms

Mesocosm study data

NOEAEC mg l⁻¹

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

Rat SF=100

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

0.5

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)

None allocated

Rat SF=100

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

European MRLs

EU MRL pesticide database

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

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
USEPA - possible human carcinogen

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising

CLP classification 2013

Environment: H400, H410

EC Risk Classification

Xn - Harmful: R22
Xi - Irritant: R36/38

EC Safety Classification

S22, S26, S36/37

WHO Classification

III (Slightly hazardous)

UN Number

2811

Waste disposal & packaging

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

Record last updated:	23/12/2020
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