Mesitylene

Mesitylene	Last updated: 10/09/2026
(Also known as: 3,5-dimethyltoluene; s-trimethylbenzene)

SUMMARY

Hazard alerts

The following Pesticide Hazard Tricolour (PHT) 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. The alerts for Highly Hazardous Pesticides (HHPs) are based on applying the FAO/WHO (Type 1) and the PAN (Type II) criteria to PPDB data. Further details on the HHP indicators are given in the tables below. Neither the PHT nor the HHP hazard alerts take account of usage patterns or exposure, thus they do not represent risk.

PHT: Environmental fate	PHT: Ecotoxicity	PHT: Human health	Highly Hazardous Pesticide
	Ecotoxicity Moderate alert: Fish acute ecotoxicity: Moderate; Fish chronic ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Daphnia chronic ecotoxicity: Moderate Warning: Significant data are missing	Human health High alert: Neurotoxicant Warning: Significant data are missing

GENERAL INFORMATION

Description

Mesitylene does not exhibit pesticidal activity but is used in pesticide formulations primarily as a high‑aromatic, high‑boiling organic solvent to dissolve hydrophobic actives, stabilise emulsifiable concentrates and control evaporation behaviour

GB regulatory status

GB Retained EC Regulation 1107/2009 status

Not applicable - not a ppp. May be authorised at national level under different legislation

Date GB regulatory inclusion expires

Not applicable

GB LERAP status

Not applicable

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Not applicable - not a ppp. May be authorised at national level under different legislation

Dossier rapporteur/co-rapporteur

Not applicable

Date EC 1107/2009 inclusion expires

Not applicable

EU Candidate for substitution (CfS)

Not applicable

Listed in EU database

Not applicable

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

Mesitylene is one of three structural (constitutional) isomers of trimethylbenzene, the others being 1,2,3-trimethylbenzene (hemimellitene) and 1,2,4-trimethylbenzene (pseudocumene). The three isomers have the same molecular formula but differ in the positions of the three methyl groups on the benzene ring. Mesitylene has the particularly symmetrical 1,3,5-substitution pattern, with the methyl groups evenly spaced around the ring. It does not exhibit stereoisomerism.

Chemical formula

C₉H₁₂

Canonical SMILES

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

Isomeric SMILES

International Chemical Identifier key (InChIKey)

AUHZEENZYGFFBQ-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C9H12/c1-7-4-8(2)6-9(3)5-7/h4-6H,1-3H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
mesitylene	-

General status

Pesticide type

Other substance

Substance groups

Aromatic hydrocarbon

Minimum active substance purity

Known relevant impurities

Substance origin

Natural

Mode of action

Substance does not exhibit pesticidal activity

CAS RN

108-67-8

EC number

203-604-4

CIPAC number

US EPA chemical code

PubChem CID

7947

Molecular mass (Da)

120.19

PIN (Preferred Identification Name)

1,3,5-trimethylbenzene

IUPAC name

1,3,5-trimethylbenzene

CAS name

sym-trimethylbenzene

Global Governance status: Listed (✓) under

UK Poisons List Order 1972	Rotterdam Convention	Montreal Protocol
XNo The Poisons List Order 1972	XNo Rotterdam Convention	XNo Montreal Protocol
Stockholm Convention	OSPAR	EU Water Framework Directive
XNo Stockholm Convention	XNo OSPAR	XNo EU Water Framework Directive

Relevant Environmental Water Quality Standards

Forever chemical

Highly Hazardous Pesticide (HHP)

Type I

Type II

Other status information

REACH registered

Herbicide Resistance Class (HRAC MoA class)

Not applicable

Herbicide Resistance Class (WSSA MoA class)

Not applicable

Insecticide Resistance Class (IRAC MoA class)

Not applicable

Fungicide Resistance Class (FRAC MOA class)

Not applicable

Examples of recorded resistance

Physical state

Liquid with a sweet odour

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1837, first synthesised

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

Example products using this active

Example products using this substance as a possible coformulant

Selected: Cabadex (Open in PFC)

Selected: Celadon (Open in PFC)

Selected: Centurion Plus (Open in PFC)

Selected: Hunter (Open in PFC)

Selected: Slalom (Open in PFC)

Selected: Starane XL (Open in PFC)

Formulation and application details

Mesitylene is supplied commercially as a liquid.

Commercial production

Commercial mesitylene is predominantly obtained from petroleum-derived aromatic hydrocarbon streams, particularly during refinery processes such as catalytic reforming and subsequent separation/fractionation. It can also be produced synthetically by acid-catalysed alkylation of benzene or related processes, but petroleum-derived C9 aromatic streams are important industrial sources.

Impact on climate of production and use

Mesitylene has a petrochemical-derived carbon footprint, because commercial production is predominantly associated with petroleum refining and the processing of C9 aromatic hydrocarbon streams. Its embodied GHG emissions therefore arise mainly from crude-oil extraction and transport, refinery operations, catalytic reforming, separation/fractionation and purification, with additional emissions associated with producing the electricity and heat used in processing. Because mesitylene is usually recovered as a co-product/by-product of refinery aromatic streams, allocating the upstream emissions specifically to mesitylene is difficult and the result depends strongly on the allocation method used. Its relatively high carbon content (C₉H₁₂) also means that, if released and ultimately oxidised or combusted, its carbon is converted predominantly to carbon dioxide, giving approximately 3.66 kg CO₂ per kg of mesitylene carbon, or about 3.63 kg CO₂ per kg mesitylene if completely oxidised. In a pesticide formulation, however, the quantity of mesitylene is normally small relative to the active ingredient, so its contribution to the formulation’s overall cradle-to-gate carbon footprint will depend principally on the concentration used and the emission factor assigned to the aromatic solvent.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

Solubility - In water at 20 °C at pH 7 (mg l⁻¹)

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

Melting point (°C)

Boiling point (°C)

163

Degradation point (°C)

Flashpoint (°C)

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

Log P

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

0.864

at 25 °C

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

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

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

Surface tension (mN m⁻¹)

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days)

DT₅₀ (typical)

DT₅₀ (lab at 20 °C)

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

Soil mineralisation

Aerobic (at 20 °C)

Anaerobic (at 20 °C)

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)

K_oc (mL g⁻¹)

Notes and range

Freundlich

K_f (mL g⁻¹)

K_foc (mL g⁻¹)

¹/_n

Notes and range

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

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

Value

Cannot be calculated

Note

Potential for particle bound transport index

Potential for loss via drain flow

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

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)

> 5000

Rat

Low

Mammals - Short Term Oral NOAEL (mg kg⁻¹ bw d⁻¹)

Mammals - Long Term (Chronic) Oral NOAEL (mg kg⁻¹ bw d⁻¹)

Birds - Acute LD₅₀ (mg kg⁻¹)

Birds - Short term dietary LC₅₀ (mg kg⁻¹ bw d⁻¹)

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

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

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

Soil micro-organisms

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Non-target plants

Vegetative vigour ER₅₀ (g ha⁻¹)

Seedling emergence ER₅₀ (g ha⁻¹)

Honeybees (Apis 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)

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)

Beneficial insects (Predatory mites)

Beneficial insects (Ground beetles)

Beneficial insects (Butterflies)

Contact

Notes

Oral

Notes

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

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

4.8

Oncorhynchrus mykiss

Moderate

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

0.38

Oncorhynchrus mykiss

Moderate

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

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

2.14

Daphnia magna

Moderate

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

> 0.35

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 (free-floating, fonds growth, fresh) - 7 day (mg l⁻¹)

Aquatic plants (rooted, growth rate, fresh) - 14 day (mg l⁻¹)

Algae - Acute (growth rate, fresh; mg l⁻¹) (ErC₅₀ 72 hr)

1.29

Desmodesmus subspicatus

Moderate

Algae - Chronic (growth rate, fresh; mg l⁻¹)

Mesocosm study data

NOEAEC mg l⁻¹

Marine bivalves

Regulatory Threshold Levels (RTLs)

Note: These RTLs have been calculated using the regulatory approach used in the European Union and based on ecotoxocity values in the PPDB.

Species group

RTL

Notes

Mammals

500

Worst case of acute and chronic mammals

Birds

No data

No data for acute and chronic birds

Soil organisms

No data

No data for acute and chronic earthworms

Terrestrial plants

No data

No data for non-target plants vegetative vigour and seedling emergence

Pollinators

No data

No data for contact and oral honeybees

Arthropods

No data

No data for parasitic wasps and predatory mites

Fish

0.038

Worst case of temperate acute and chronic fish

Aquatic invertebrates

0.0214

Worst case of temperate acute and chronic aquatic invertebrates

Aquatic plants

0.129

Worst case of free-floating plants, rooted plants, acute and chronic algae

HUMAN HEALTH AND PROTECTION

General

Property

Value

Source; quality score; and other information

Interpretation

Threshold of Toxicological Concern (Cramer Class)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 5000

Rat

Low

Mammals - Short Term Oral NOAEL (mg kg⁻¹ bw d⁻¹)

Mammals - Long Term (Chronic) Oral NOAEL (mg kg⁻¹ bw d⁻¹)

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

Mammals - Inhalation LC₅₀ (mg l⁻¹)

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

Occupational

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 (hazard-based)

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

CNS depressant

Handling issues

Property

Value and interpretation

General

Flammable liquid

CLP classification 2013

Handling: H226
Health: H335
Environment: H411

WHO Classification

UN Number

UN2325

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

mesitylene

French

German

Danish

Italian

Spanish

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:

10/09/2026

Contact:

aeru@herts.ac.uk

Please cite as:

Tzilivakis, J., Lewis, K.A., Green, A. and Warner, D.J. (2026) A decade of growth and impact of the Pesticide Properties Database (PPDB). Human and Ecological Risk Assessment: An International Journal, 1–26. DOI: 10.1080/10807039.2026.2702066

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

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