Diazinon (Ref: OMS 469)

Diazinon (Ref: OMS 469)	Last updated: 01/11/2024
(Also known as: dimpylate; ENT 19507)

SUMMARY

Diazinon is a general purpose insecticide. It is moderately soluble and highly volatile. Based on its chemical properties it has a low risk of leaching to groundwater however, incidents of contamination have been noted and it should be considered a potential groundwater pollutant. It is non-persistent in soil but stable in aqueous environments. It is listed as a severe marine pollutant. Moderately toxic to mammals and earthworms. In humans and other mammals it is a neurotoxicant. Considered highly toxic to most aquatic organisms, honeybees and birds.

GENERAL INFORMATION

Description

An organophosphate topical insecticide for parasite and fly control

Availability status

Current

Introduction & key dates

1953, first reported

Examples of veterinary uses

Used as a spray or dip for the control of lice and ticks in cattle. It is also used to control flies in livestock housing and fleas on domestic pets.

Examples of species treated

Cattle; Sheep; Cats; Dogs

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

None

Chemical formula

C₁₂H₂₁N₂O₃PS

Canonical SMILES

CCOP(=S)(OCC)OC1=NC(=NC(=C1)C)C(C)C

Isomeric SMILES

S=P(OCC)(OCC)Oc1nc(nc(c1)C)C(C)C

International Chemical Identifier key (InChIKey)

FHIVAFMUCKRCQO-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C12H21N2O3PS/c1-6-15-18(19,16-7-2)17-11-8-10(5)13-12(14-11)9(3)4/h8-9H,6-7H2,1-5H3

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Insecticide, Antiparasitic, Sheep dip

Substance groups

Organophosphate insecticide; Organophosphate acaricide; Organothiophosphate insecticide; Organothiophosphate acaricide; Oganophosphate repellent

Minimum active substance purity

950 g kg⁻¹ (without stabilizer)

Known relevant impurities

EU dossier - O,S-TEPP, S,S-TEPP, TEPP24 and diazoxon

Substance origin

Synthetic

Mode of action

Non-systemic with respiratory, contact and stomach action. Acetylcholinesterase (AChE) inhibitor.

Molecular targets

[Cholinesterase, Inhibitor]

CAS RN

333-41-5

EC number

206-373-8

CIPAC number

US EPA chemical code

057801

PubChem CID

3017

CLP index number

015-040-00-4

Therapeutic Class

Antiparasitic products, insecticides & repellents: Ecoparasiticides, insecticides & repellents

ATCvet Code

QP53AF03

Controlled Drug?

Regulation 37/2010 MRL Classification

Allowed substance (Table 1: Bovine, Ovine, Caprine, Porcine)

Molecular mass

304.35

PIN (Preferred Identification Name)

O,O-diethyl O-[6-methyl-2-(propan-2-yl)pyrimidin-4-yl] phosphorothioate

IUPAC name

O,O-diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphorothioate

CAS name

O,O-diethyl O-(6-methyl-2-(1-methylethyl)-4-pyrimidinyl) phosphorothioate

Other status information

Potential groundwater contaminant; Severe Marine Pollutant; Chemical subject to PIC regulations

Relevant Environmental Water Quality Standards

UK statutory standard for surface water quality: ‘Good’ for freshwater, transitional and coastal waters 0.01 µg l⁻¹, 0.02 µg l⁻¹ 95th percentile

Physical state

Colourless to dark brown liquid

Formulations

Property

Product

Manufacturer

Authorisation Route

Legal Class (GB/UK)

Example products (past and present) using this active

Armitage Pet Care Flea & Tick Collar

Virbac S.A.

Not licensed

Bob Martin Flea & Tick Collar

Virbac S.A.

Not licensed

Canac Dog Flea & Tick Collar

Virbac S.A.

Not licensed

Coopers Ectoforce Sheep Dip

Schering-Plough Ltd

Not licensed

Formulation and application details

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

Moderate

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

250000

Ethyl acetate

9000000

Acetone

9000000

Methanol

9000000

Toluene

Melting point (°C)

Not applicable

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

140

Flashpoint (°C)

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

4.90 X 10⁰³

Calculated

Log P

3.69

High

Fat solubility of residues

Solubility

Soluble

Data type

Regulatory data - observed in metabolism and farm animal feeding studies

Density (g ml⁻¹)

1.11

Dissociation constant pKa) at 25 °C

2.6

Strong acid

Vapour pressure at 20 °C (mPa)

11.97

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)

6.09 X 10^-02

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

49.6

24 hr

Volatilisation is potentially a concern for short and long range air transport

From soil surface

10.4

24 hr

Volatilisation is not considered critical for air pollution

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

Maxima at 246nm = 4050, 290nm = 20.86

Surface tension (mN m⁻¹)

49.5

at 20°C

Refractive Index

Environmental release

Degradation

Property

Value

Source; quality score; and other information

Interpretation

Soil degradation (days) (aerobic)

DT₅₀ (typical)

9.1

Non-persistent

DT₅₀ (lab at 20 °C)

9.1

Non-persistent

DT₅₀ (field)

18.4

Non-persistent

DT₉₀ (lab at 20 °C)

209

Persistent

DT₉₀ (field)

Note

EU dossier range lab studies DT₅₀ range 8-23 days, DT₉₀ range 46-372 days; field studies Germany DT₅₀ 7.5-29.3 days, DT₉₀ range 24.9-97 days; Other sources: DT₅₀ 40 days (DW4)

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Stable

Note

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

Value

138

Persistent

Note

pH variable: DT₅₀ 12 days at pH 5, 77 days at pH 9

Water-sediment DT₅₀ (days)

10.4

Fast

Water phase only DT₅₀ (days)

4.3

Moderately fast

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

[Grapes: 4.9 days @ 25 DegC; 9.8 days @ 4 DegC; Field study], [Mushroom (Agaricus bisporus): 4.4 days @ 25 DegC; 4.47 days @ 4 DegC; 20.4 days @ -18 DegC; Lab study]

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d (mL g⁻¹)

27.1

Slightly mobile

K_oc (mL g⁻¹)

609

Notes and range

EU dossier K_d range 3.7-113.5 mL g⁻¹, K_oc range 430-841 mL g⁻¹, Soils=2; Other literature studies: K_d range 0.84-19.72 mL g⁻¹; K_oc range 254-3779 mL g⁻¹, Soils=25

Freundlich

K_f (mL g⁻¹)

4.1

Slightly mobile

K_foc (mL g⁻¹)

643

¹/_n

0.860

Notes and range

EU dossier K_f range1.4-7.6 mL g⁻¹, K_foc range 413-760 mL g⁻¹, ¹/_n range 0.820-0.901, Soils=4; Other literature studies: K_f range 0.70-25.73 mL g⁻¹, K_foc range 259-4175 mL g⁻¹, ¹/_n range 0.79-1.25, Soils = 25

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.51

Calculated

Low leachability

Bio-concentration factor

BCF (l kg⁻¹)

500

(Other literature log BCF range 0.7-3.5 (R3))

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

pyrimidinol (Ref: GS-27550)

Major fraction

0.818

2-(1-hydroxy-1-methyl)-ethyl-4-methyl-6-hydroxpyrimidine (Ref: GS-31144)

Minor fraction

Known groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

2-(1-hydroxymethyl)-ethyl-4-methyl-6-hydroxypyrimidine (Ref: CL-XIX-29)

Animal

2-isopropyl-4-hydroxymethyl-6-hydroxypyrimidine (Ref: JAK-III-57)

Animal

hydroxydiazinon (Ref: CGA 14128)

Animal; Plant

tetraethyl pyrophosphate (Ref: ENT 18771 )

TEPP

Not applicable

O,O,O,O-tetraethyl-thiopyrophosphate

O,S-TEPP

Not applicable

O,O,O,O-tetraethyl-dithiopyrophosphate

S,S-TEPP

Not applicable

2-(1-hydroxy-1-methyl)-ethyl-4-methyl-6-hydroxpyrimidine (Ref: GS 31144)

Rat (Urine); Animal

O,O-diethyl O-(2-isopropyl-4-methylpyrimid-6-yl)phosphate
Note: CAS = 962-58-3; Toxic

diazoxon

Animal

diazinon hydroxylate

Animal

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

1139

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Rat

High

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

1.44

Anas platyrhynchos

High

Birds - Short term dietary (LC₅₀/LD₅₀)

8 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)

Moderate

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

Soil micro-organisms

Nitrogen mineralisation: No significant adverse effect
Carbon mineralisation: No significant adverse effect

Dose: 80 mg kg⁻¹ soil 28 Day

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)

0.13

Apis mellifera

High

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

0.09

Apis mellifera

High

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

Chronic

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)

0.007

Megachile rotundata

High

Mode of exposure

Contact

Other bee species (2)

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

0.12

Nannotrigona perilampoides

High

Mode of exposure

Contact

Beneficial insects (Ladybirds)

Beneficial insects (Lacewings) as % Mortality at doses <1170 kg ha⁻¹

Chrysoperla carnea

Beneficial insects (Parasitic wasps) as Mortality LR₅₀ g ha⁻¹ 48 hr

811

Aphidius rhopalosiphi

Beneficial insects (Predatory mites) as Mortality LR₅₀ g ha⁻¹ 7 day

0.153

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)

3.1

Oncorhynchus mykiss

Moderate

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

0.7

Oncorhynchus mykiss

Moderate

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

> 2.08

Danio rerio

Moderate

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

0.001

Daphnia magna

High

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

0.00056

Daphnia magna

High

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

0.0002

Ceriodaphnia dubia LC₅₀

High

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

0.0042

Americamysis bahia

High

Sediment dwelling organisms - Acute 96 hour LC₅₀ (mg l⁻¹)

0.023

Chironomus riparius

High

Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)

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

15.9

Chironomus dilutus Growth

Moderate

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

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

6.4

Unknown species

Moderate

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

> 10

Unknown species

Low

Mesocosm study data

NOEAEC mg l⁻¹

0.0024

Fish

NOEAEC mg l⁻¹

Marine bivalves – Acute EC₅₀ development (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)

1139

Rat

Moderate

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 5.0

Rat

Other Mammal toxicity endpoints

Intraperitoneal LD₅₀ = 65.0 mg kg⁻¹

Rat

Intratracheal LD₅₀ = 210 mg kg⁻¹

Rat

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

0.0002

Dog SF=100

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

0.025

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)

0.0002

Dog SF=100

Dermal penetration studies (%)

1.7-40.0

concentration dependent

Dangerous Substances Directive 76/464

List I; List II

Exposure Routes

Public

Possible risk to bystanders by inhalation

Occupational

Risk of exposure by dermal and inhalation routes
Personal protection clothing and equipment must be worn

Mammalian dose elimination route and rate

Quickly degrades, two main pyrimidinol metabolites are formed which are largely eliminated via urine, Rate varies with species.

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

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

IARC Group 2A carcinogen; US EPA - not likely to be a human carcinogen
Endocrine issues - Estrogenic effect

Handling issues

Property

Value and interpretation

General

Not explosive
IMDG Transport Hazard Class 6.1
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Health: H302
Environment: H400, H410

WHO Classification

II (Moderately hazardous)

UN Number

UN2811

Waste disposal & packaging

Packaging Group II (moderate danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

diazinon

French

diazinon

German

Diazinon

Danish

diazinon

Italian

diazinone

Spanish

diazinon

Greek

diazinon

Polish

diazynon

Swedish

diazinon

Hungarian

diazinon

Dutch

diazinon

Norwegian

Record last updated:	01/11/2024
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