1-naphthylacetic acid

1-naphthylacetic acid	Last updated: 29/08/2024
(Also known as: NAA; alpha-NAA; naphthylacetic acid; 1-NAA; 1-naphthaleneacetic acid)

SUMMARY

1-naphthylacetic acid is a synthetic auxin used as a plant growth regulator. It has a low aqueous solubility and low volatility but may, under certain conditions, be persistent in soil systems. It is not expected to be persistent in aquatic systems. It is moderately toxic to most biodiversity. 1-naphthylacetic acid has a moderate oral toxicity to humans, is a recognised irritant and may also be a reproduction/developmental toxin.

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 High alert: GUS: High leachability	Ecotoxicity Moderate alert: Fish acute ecotoxicity: Moderate; Fish chronic ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate	Human health High alert: Reproduction/development effects

GENERAL INFORMATION

Description

A synthetic auxin used as a plant growth regulator to control top fruit pre-harvest fruit drop, for fruitlet thinning and for striking hard and softwood cuttings. Also a metabolite.

Example pests controlled

Fruit drop

Example applications

Top fuit including apples, pears, plums, cherries; Potatoes

Efficacy & activity

Appearance and life cycle

Availability status

Current

Introduction & key dates

1939, first reported; circa 1960, introduced

Taxonomic classification

UK regulatory status

UK COPR regulatory status

Approved

Date COPR inclusion expires

31/12/2026

UK LERAP status

None

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Hungary/France

Date EC 1107/2009 inclusion expires

31/05/2026

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

Known to be also used in the following countries

Chemical structure

Isomerism

None

Chemical formula

C₁₂H₁₀O₂

Canonical SMILES

C1=CC=C2C(=C1)C=CC=C2CC(=O)O

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

PRPINYUDVPFIRX-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C12H10O2/c13-12(14)8-10-6-3-5-9-4-1-2-7-11(9)10/h1-7H,8H2,(H,13,14)

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
1-naphthylacetic acid	-

General status

Biopesticide type

Plant Growth Regulator

Metabolite Type

Soil, Groundwater

Substance groups

Auxin PGR; Naphthalene compound

Minimum active substance purity

980 g kg⁻¹

Known relevant impurities

EU dossier - 1-NAD

Substance origin

Synthetic

Mode of action

Absorbed through roots, stems and leaves, demonstrates auxin-like activity

Substance source

Substance production

Uses

Target pests

Target host

Farming system suitability

CAS RN

86-87-3

EC number

201-705-8

CIPAC number

313

US EPA chemical code

056002

PubChem CID

6862

CLP index number

No data found

Molecular mass

186.21

PIN (Preferred Identification Name)

IUPAC name

2-naphthalen-1-ylacetic acid

CAS name

1-naphthylacetic acid

Other status information

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

Light tan to light pink flaky powder

Related substances & organisms

indolylacetic acid

Formulations

Property

Product

Manufacturer

Example products

Formulation and application details

Usually supplied as wettable powders, soluble concentrates and dustable powders

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

16.8

Low

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

588

n-Heptane

24340

Xylene

250000

Methanol

133700

Acetone

Melting point (°C)

130

Boiling point (°C)

322.2

Degradation point (°C)

360

Flashpoint (°C)

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

9.55 X 10^-01

Calculated

Log P

-0.02

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.233

Dissociation constant pKa) at 25 °C

4.23

Weak acid

Vapour pressure at 20 °C (mPa)

1.27

Low volatility. 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)

3.03 X 10^-04

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

Acidic solution: 233nm = 72500
Neutral solution: 233nm = 79600
Basic solution: 282nm = 7020

Surface tension (mN m⁻¹)

35.9

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)

41.7

Moderately persistent

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

136

Persistent

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 6.4 days (sandy loam) - 77 days (loamy sand), DT₉₀ range 14.7-257 days; General literature states DT₅₀ 30-50 days

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

2.9

Moderately fast

Note

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

Value

Stable

Note

Stable pH 4,7 & 9

Water-sediment DT₅₀ (days)

9.5

Fast

Water phase only DT₅₀ (days)

7.0

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

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d (mL g⁻¹)

1.39

Moderately mobile

K_oc (mL g⁻¹)

84.8

Notes and range

EU dossier K_d range 0.42-2.72 mL g⁻¹, K_oc range 46.1-138.0 mL g⁻¹, Soils=3

Freundlich

K_f (mL g⁻¹)

1.39

Mobile

K_foc (mL g⁻¹)

61.2

¹/_n

0.842

Notes and range

EU dossier K_f range 0.31-1.73, K_foc range 44.65-86.53 mL g⁻¹, ¹/_n range 0.822-0.864, Soils=3

pH sensitivity

Known soil metabolites

Metabolite

Major/Minor fraction

$Click here for further information on Major/Minor fraction$

Estimated maximum occurrence fraction

Notes

1-napthoic acid

Major fraction

0.247

DT50 ~ 6 days

Known groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

1-naphthalene methanol

Water

1-methyl naphthalene

Water

1-naphthaldehyde

Water

phthalic acid

Water

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 1750

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)

> 2510

Coturnix japonica

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

> 1606 mg kg bw⁻¹ day⁻¹

Coturnix japonica

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

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

> 1000

Eisenia foetida

Low

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

Soil micro-organisms

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

0.1 mg kg⁻¹ 1-NAA

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)

> 120

Apis mellifera

Low

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

> 120

Apis mellifera

Low

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)

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) as % Mortality at dose 440 mg l⁻¹

Coccinella septempunctata Dipped Larva

Beneficial insects (Lacewings)

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

42.0

Aphidius rhopalosiphi

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

42.0

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)

> 56

Oncorhynchus mykiss

Moderate

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

Oncorhynchus mykiss

Moderate

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

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

> 56

Daphnia magna

Moderate

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

> 22

Daphnia magna

Low

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)

5.09

Lemna gibba

Moderate

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

18.05

Pseudokirchneriella subcapitata Biomass

Low

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

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)

> 1750

Rat

Moderate

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 0.45

Rat (whole body)

Other Mammal toxicity endpoints

Intraperitoneal LD₅₀ = 100 mg kg⁻¹

Rat

Subcutaneous LD₅₀ = 733 mg kg⁻¹

Mouse

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

0.10

Rat SF=150

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

0.10

Rat SF=150

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

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

0.07

Rat SF=170

Dermal penetration studies (%)

default

Dangerous Substances Directive 76/464

Exposure Routes

Public

Acceptable risk for proposed uses

Occupational

PPE/PPC advised to mitigate exposure risks

Mammalian dose elimination route and rate

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

Possible blood toxicant

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Health: H302, H315, H318, H319. H335
Environment: H412

WHO Classification

III (Slightly hazardous)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

Limited shelf-life. Store in a cool and dry place

TRANSLATIONS

Language

Name

English

1-naphthylacetic acid

French

acide naphthylacetique

German

Naphthyl-1-essigsaeure

Danish

Italian

Spanish

acido 1-naftilacetico

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	29/08/2024
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