Flurprimidol (Ref: EL 500)

Flurprimidol (Ref: EL 500)	Last updated: 25/05/2025
(Also known as: flurprimidole)

SUMMARY

Flurprimidol is a plant growth regulator used to retard growth in a wide range of mono- and dicotyledonous weed species. It is moderately soluble in water, has a low volatility but there is some risk of drift under certain conditions. Generally, it is not persistent in soils or water-sediment systems. Regarding human health there is some concern that it may be a reproduction/developmental toxin. Oral mammalian toxicity is moderate. Toxicity to biodiversity is low to moderate.

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: GUS: Transition state; Drainflow: Moderately mobile	Ecotoxicity Moderate alert: Fish acute ecotoxicity: Moderate; Fish chronic ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Daphnia chronic ecotoxicity: Moderate; Earthworms acute ecotoxicity: Moderate; Earthworms chronic ecotoxicity: Moderate	Human health High alert: Reproduction/development effects

GENERAL INFORMATION

Description

A plant growth regulator used to retard growth in a wide range of mono- and dicotyledonous weed species

Example pests controlled

Growth - reduces internodal elongation to improve plant shape

Example applications

Turf; Ornamental trees

Efficacy & activity

Availability status

Current

Introduction & key dates

1989, registered USA

GB regulatory status

GB COPR regulatory status

Not approved

Date COPR inclusion expires

Expired

GB LERAP status

No UK approval for use as a plant protection agent

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Not approved

Dossier rapporteur/co-rapporteur

Finland

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

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

USA

Chemical structure

Isomerism

A chiral molecule. Substance is racemic.

Chemical formula

C₁₅H₁₅F₃N₂O₂

Canonical SMILES

CC(C)C(C1=CC=C(C=C1)OC(F)(F)F)(C2=CN=CN=C2)O

Isomeric SMILES

International Chemical Identifier key (InChIKey)

VEVZCONIUDBCDC-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C15H15F3N2O2/c1-10(2)14(21,12-7-19-9-20-8-12)11-3-5-13(6-4-11)22-15(16,17)18/h3-10,21H,1-2H3

2D structure diagram/image available?

Yes

General status

Pesticide type

Plant Growth Regulator; Herbicide

Substance groups

Pyrimidinyl PGR; Pyrimidinyl herbicide

Minimum active substance purity

983 g kg⁻¹

Known relevant impurities

EU dossier - none declared

Substance origin

Synthetic

Mode of action

Absorbed by leaves and roots. Gibberellin biosynthesis inhibitor.

CAS RN

56425-91-3

EC number

611-386-0

CIPAC number

696

US EPA chemical code

125701

PubChem CID

73668

CLP index number

No data found

Molecular mass

312.29

PIN (Preferred Identification Name)

IUPAC name

(RS)-2-methyl-1-pyrimidin-5-yl-1-(4-trifluoromethoxyphenyl)propan-1-ol

CAS name

α-(1-methylethyl)-α-(4-(trifluoromethoxy)phenyl)-5-pyrimidinemethanol

Other status information

Chemical subject to PIC regulations

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)

Not applicable

Fungicide Resistance Class (FRAC MOA class)

Not applicable

Examples of recorded resistance

Physical state

White to pale straw coloured crystals

Formulations

Property

Value

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

Elanco

Example products using this active

Topflor
Cutless

Formulation and application details

Usually supplied as a micro-emulsion that is mixed with water

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

114

Moderate

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

1530000

Acetone

144000

Toluene

1200000

Ethyl acetate

1990000

Methanol

Melting point (°C)

95.3

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

200

Flashpoint (°C)

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

2.19 X 10⁰³

Calculated

Log P

3.34

High

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.34

Dissociation constant pKa) at 25 °C

No applicable

No dissociation

Vapour pressure at 20 °C (mPa)

0.1

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)

2.74 X 10^-04

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

24.2

24 hr

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

From soil surface

6.6

24 hr

Volatilisation is not considered critical for air pollution

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

Neutral solution: 204.8nm = 19100
Acidic solution: 203.8nm = 18000
Basic solution: 218.6nm = 9140

Surface tension (mN m⁻¹)

51.9

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)

178

Persistent

DT₅₀ (field)

11.5

Non-persistent

DT₉₀ (lab at 20 °C)

563

Very persistent

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 45-260 days (mean across 3 temperature and 4 soils), DT₅₀ 83-403 days for peat, DT₉₀ range 179-1338 days, field studies range 5-23 days (USA); Other sources: 548 days (DW3)

Dissipation rate RL₅₀ (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

23.1

Note

Turfgrass, n=1; Watermilfoil, aquatic situation, RL₅₀=9.0 days

Aqueous photolysis DT₅₀ (days) at pH 7

Value

1.4

Moderately fast

Note

DT₅₀ 29 days natural light in glasshouse conditions

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

Value

Stable

Note

Stable pH 4 to pH 9 25-50 °C

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)

Moderately mobile

K_oc (mL g⁻¹)

263

Notes and range

Freundlich

K_f (mL g⁻¹)

2.8

Moderately mobile

K_foc (mL g⁻¹)

184

¹/_n

0.87

Notes and range

EU dossier K_f range 1.7-3.4 mL g⁻¹, kfoc range 131-23 mL g⁻¹, ¹/_n range 0.83-0.89, Soils=4

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.84

Calculated

Transition state

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

Value

3.67 X 10^-02

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Moderately mobile

Calculated

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

3.758

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)

35.1

Whole fish

Low potential

CT₅₀ (days)

0.53

Known soil and groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

2-methyl-1-[3-(pyrimidin-5-yl)-4-(trifluoromethoxy)phenyl]propan-1-one

Metabolite D

Water (Photolysis)

2-methyl-1-[5-(5-pyrimidinyl)-4-(trifluoromethoxy)-1,5-cyclohexadien-1-yl]-1-propanone

Metabolite E

Water (Photolysis)

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

709

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)

> 2000

Anas platyrhynchos

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

> 5000 mg kg feed⁻¹

Anas platyrhynchos

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

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

= 164

Eisenia foetida corr

Moderate

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

31.3

Eisenia foetida corr

Moderate

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

89.2

Aphidius rhopalosiphi

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

> 29.6

Typhlodromus pyri

Beneficial insects (Ground beetles)

0% Mortality at dose 0.6 kg ha⁻¹

Poecilus cupreus

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

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

18.3

Oncorhynchus mykiss

Moderate

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

0.42

Lepomis macrochirus

Moderate

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

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

11.8

Daphnia magna

Moderate

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

1.7

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

Aquatic plants (rooted, growth) - Acute 14 day EC₅₀, biomass (mg l⁻¹)

0.075

Myriophyllum spicatum 28d NOEC

Moderate

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

0.84

Pseudokirchneriella subcapitata

Moderate

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)

709

Rat

Moderate

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

5000

Rabbit

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 5.23

Rat 4 hr (nose only)

Other Mammal toxicity endpoints

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

0.003

Rat SF=300

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

0.09

Rabbit 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)

0.003

Dermal penetration studies (%)

6.0-15.0

concentration dependent

Dangerous Substances Directive 76/464

List II

Exposure Routes

Public

Negligible risk to bystanders

Occupational

Possible risk of exposure from handheld equipment even when PPE/PPC is used

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

0.1

EU Dir 89/778/EC limit

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

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

Possible liver and kidney toxicant

Handling issues

Property

Value and interpretation

General

Prevent generation of dust
Not explosive or oxidising
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Health: H302, H315, H319

WHO Classification

II (Moderately hazardous)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

flurprimidol

French

flurprimidol

German

Flurprimidol

Danish

flurprimidol

Italian

flurprimidol

Spanish

flurprimidol

Greek

Polish

fluroprimidol

Swedish

flurprimidol

Hungarian

Dutch

Norwegian

Record last updated:	25/05/2025
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