Thymol

Thymol	Last updated: 31/10/2024
(Also known as: isopropyl-m-cresol; 2-isopropyl-5-methylphenol; thyme camphor; thymic acid; hydroxy cymene)

SUMMARY

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; Daphnia acute ecotoxicity: Moderate; Earthworms acute ecotoxicity: Moderate; Earthworms chronic ecotoxicity: Moderate	Human health High alert: Genotoxic; Reproduction/development effects

GENERAL INFORMATION

Description

A substance of the monoterpene phenol class with a range of activities and uses including as a fungicide, antimicrobial treatment and antiseptic

Example pests controlled

Botrytis; Powdery mildew; Mites

Example applications

Bees; Livestock; Grapes; Top fruit

Efficacy & activity

Availability status

Current

Introduction & key dates

1842, first synthesised; 1964, first registered USA

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

30/11/2031

GB LERAP status

No UK approval for use as a pesticide

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Spain/Greece

Date EC 1107/2009 inclusion expires

30/04/2026

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

Egypt, Morocco

Chemical structure

Isomerism

Chemical formula

C₁₀H₁₄O

Canonical SMILES

CC1=CC(=C(C=C1)C(C)C)O

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

MGSRCZKZVOBKFT-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C10H14O/c1-7(2)9-5-4-8(3)6-10(9)11/h4-7,11H,1-3H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
thymol	-

General status

Pesticide type

Insecticide, Fungicide, Other substance, Veterinary substance, Semiochemical

Metabolite Type

Biocide

Substance groups

Plant-derived substance

Minimum active substance purity

>90%; 990 g kg⁻¹

Known relevant impurities

EU dossier - none declared

Substance origin

Natural, Biocide, Biodrug

Mode of action

Contact, GABAergic activity and also repels vertebrate pests by a non-toxic mode of action but is toxic to micro-organisms

CAS RN

89-83-8

EC number

201-944-8

CIPAC number

969

US EPA chemical code

080402

PubChem CID

Molecular mass

150.22

PIN (Preferred Identification Name)

IUPAC name

5-methyl-2-isopropyl-1-phenol

CAS name

phenol, 5-methyl-2-(1-methylethyl)-

Other status information

Recognised water pollutant; UK registered Commodity Substance

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)

UNE

Fungicide Resistance Class (FRAC MOA class)

Not applicable

Examples of recorded resistance

Physical state

White crystalline solid with a herbal odour

Related substances & organisms

geraniol

eugenol

Formulations

Property

Value

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

Aldrich Chemical Company
JT baker

Example products using this active

Listerine
Bensulfoid Lotion

Formulation and application details

Available in a wide variety of formulations including capsule suspensions, wipe-on products, dip, aerosol, immersion liquids and spot treatment. For beehives it is supplied as a slow release gel matrix

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

596

High

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

>250000

p-Xylene

>250000

Methanol

>250000

Ethyl acetate

200000

n-Heptane

Melting point (°C)

48.75

Boiling point (°C)

232.3

Degradation point (°C)

Flashpoint (°C)

105.5

(closed cup)

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

2.75 X 10⁰³

Calculated

Log P

3.44

High

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

0.97

Dissociation constant pKa) at 25 °C

10.77

Vapour pressure at 20 °C (mPa)

3400

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)

0.86

Moderately volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

No absorption >290nm

Surface tension (mN m⁻¹)

52.3

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)

0.7

Non-persistent

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

2,2

Non-persistent

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU 2023 dossier Lab studies DT₅₀ (normalised) range 0.6-0.8 days, DT₉₀ range 1.8-2.6 days, Soils=4;

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

Note

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

Value

Note

Water-sediment DT₅₀ (days)

Water phase only DT₅₀ (days)

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)

2188

Notes and range

Data caluated using predictive software

Freundlich

K_f (mL g⁻¹)

3.06

Moderately mobile

K_foc (mL g⁻¹)

119.14

¹/_n

0.906

Notes and range

EU 2023dossier K_f range 1.021-5.361 mL g⁻¹, K_foc range 92.8-171.0 mL g⁻¹, ¹/_n range 0.830-0.958, Soils=4

pH sensitivity

None

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

-0.30

Calculated

Low leachability

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

Value

3.29 X 10^-04

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

1.97

Calculated using the Atkinson method. Assumed 1.5E+06 OH/cm³, 12 hr

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

CT₅₀ (days)

Known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

980

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

> 640

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

> 5866 mg kg bw⁻¹ day⁻¹

Colinus virginianus as product (66 g l⁻¹)

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

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

> 500

Eisenia foetida as product (66g l⁻¹) corr

Moderate

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

1.65

Eisenia andrei corr

Moderate

Soil micro-organisms

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

Dose 54.5 mg product/kg soil

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)

> 200

Apis mellifera as product (66 g l⁻¹ thymol)

Low

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

> 224.6

Apis mellifera as product (66 g l⁻¹ thymol)

Low

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

Chronic LDD₅₀ 10d

123.5

Apis mellifera as product (66 g l⁻¹ thymol)

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

> 12420

Aphidius rhopalosiphi as product (66 g l⁻¹ thymol)

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

> 12420

Typhlodromus pyri as product (66 g l⁻¹ thymol)

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)

3.0

Oncorhynchus mykiss

Moderate

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

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

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

4.9

Daphnia magna

Moderate

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

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)

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

11.7

Pseudokirchneriella subcapitata Growth

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)

Low (class I)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

980

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

Subcutaneous LD₅₀ = 243 mg kg⁻¹

Mouse

Intravenous LD₅₀ > 100 mg kg⁻¹

Mouse

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

0.07

Rat SF=600

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

0.4

Rat SF=100

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

0.4

Rat SF =100

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

0.4

Rat SF =100

Dermal penetration studies (%)

25-70

Default

Dangerous Substances Directive 76/464

Exposure Routes

Public

Acceptable for proposed uses

Occupational

PPE/PPC recommended

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

Extensively and rapidly absorbed, excreted via urine (>50% in 24hr)

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

No data found

Respiratory tract irritant

Skin irritant

Skin sensitiser

Eye irritant

Phototoxicant

No data found

General human health issues

May cause gastrointestinal problems, central hyperactivity and occasionally convulsions and coma
Possible renal, kidney and liver toxicant
May cause CNS or muscular contractions

Handling issues

Property

Value and interpretation

General

Corrosive
Not explosive or oxidising

CLP classification 2013

Health: H302, H314, H317, H318, H336

WHO Classification

Not listed (Not listed)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

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Name

English

thymol

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Swedish

Hungarian

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Record last updated:	31/10/2024
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