Indolylacetic acid

Indolylacetic acid	Last updated: 28/11/2025
(Also known as: IAA; AIA; beta-indoleacetic acid; auxins; heteroauxin; indole-3-ylacetic acid)

SUMMARY

A botanical extract that can be used as a plant growth regulator for use indoors but which does not have EU approval for use. It is highly soluble in water and volatile. Little is known about its environmental persistance but there are indications that it may be persistent under certain conditions in water. However, it is unstable in UV light. It is moderately toxic to mammals but generally not thought to present significant risk of causing problems for human health although there are uncertainties regarding its effect for reproduction and the CNS. Little is known regarding its ecotoxicology.

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
		Human health Moderate alert: Reproduction/development effects; Neurotoxicant Warning: Significant data are missing

GENERAL INFORMATION

Description

A botanical auxin extract used to improve rootings of woody plant cuttings

Example pests controlled

Growth

Example applications

Ornamentals

Efficacy & activity

Appearance and life cycle

Taxonomic classification

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

France

Date EC 1107/2009 inclusion expires

Expired

EU Candidate for substitution (CfS)

Not applicable

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; South Africa

Chemical structure

Isomerism

None

Chemical formula

C₁₀H₉NO₂

Canonical SMILES

C1=CC=C2C(=C1)C(=CN2)CC(=O)O

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

SEOVTRFCIGRIMH-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C10H9NO2/c12-10(13)6-8-5-7-3-1-2-4-9(7)11-8/h1-5,11H,6H2,(H,12,13)

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
indolylacetic acid	-

General status

Biopesticide type

Plant Growth Regulator

Substance groups

Plant-derived substance; Micro-organism derived substance

Minimum active substance purity

990 g kg⁻¹

Known relevant impurities

EU dossier - none declared

Substance origin

Natural

Mode of action

Broad-spectrum, effects cell division and elongation stimulating the formation of roots.

Substance source

A plant auxin that is produced in cells of the buds and young leaves of plants, In addition, various microorganisms have shown the ability to produce IAA, such as bacteria, actinomycetes, fungi or yeast

Uses

Yield enhancement

Target pests

None - PGR

Target host

Ornamentals

Farming system suitability

Suitable for use in all farming systems where approved for use in that country

CAS RN

87-51-4

EC number

201-748-2

CIPAC number

8186

US EPA chemical code

128915

PubChem CID

Molecular mass

175.18

PIN (Preferred Identification Name)

IUPAC name

1H-indole-3-acetic acid

CAS name

indol-3-ylacetic acid

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

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

Colourless to pale pink crystals

Related substances & organisms

1-naphthylacetic acid

Commercial

Property

Value

Availability status

Current

Introduction & key dates

Circa 1940s, developed; 1946, first introduced

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

ACF Chemiefarma
Hortus USA
Acros Organics BVBA

Example products using this active

Rhizopon A powder
Rhizopon AA
1H-Indole-3-acetic acid, 99+%

Formulation and application details

Often supplied as a dustable powder or as water soluble tablets

Commercial production

Indole-3-acetic acid is produced commercially using microbial fermentation processes. Specific strains of bacteria or fungi, such as Streptomyces fradiae or Rhizobium sp. are selected for their high production capabilities. The microorganisms are cultured under optimised conditions and incubated in a suitable medium, often supplemented with L-tryptophan, which is a precursor for Indole-3-acetic acid production. After fermentation, Indole-3-acetic acid is extracted from the culture medium and purified using techniques like thin-layer chromatography and high-performance liquid chromatography

Impact on climate of production and use

Data for the amount of life cycle GHGs produced by indolylacetic acid are not available in the public domain. However, whilst estimates vary, similar small molecules emit roughly 0.5-1.0 kg CO₂e per kg of product under conventional energy mixes.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

1500

High

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

1000000

Ethanol

65000

Diethyl ether

65000

Acetone

20000

Chloroform

Melting point (°C)

167

Boiling point (°C)

363

Degradation point (°C)

Flashpoint (°C)

171

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

2.57 X 10⁰¹

Calculated

Log P

1.41

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.576

Dissociation constant pKa) at 25 °C

4.75

Weak acid

Vapour pressure at 20 °C (mPa)

0.021

Low volatility

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

2.3 X 10^-06

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

Neutral: max at 220nm, shoulders at 200nm, 280nm

Surface tension (mN m⁻¹)

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

DT₅₀ (lab at 20 °C)

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

General literature reports rapid degradation in soil

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

Unstable in UV light

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

Value

Stable

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

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)

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)

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 (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) (EC₅₀)

> 1.69

Scenedesmus quadricauda

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

No data

No data for temperate acute and chronic fish

Aquatic invertebrates

No data

No data for temperate acute and chronic aquatic invertebrates

Aquatic plants

0.169

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)

Low (class I)

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)

> 2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 1.77

Rat

Other Mammal toxicity endpoints

Intraperitoneal LD₅₀ = 150 mg kg⁻¹

Mouse

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

Not allocated

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

Not allocated

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

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

0.055

Mouse SF=900

Dermal penetration studies (%)

11.3

Dangerous Substances Directive 76/464

Exposure Routes

Public

Not expected to pose a significant risk

Occupational

Not expected to pose a significant risk

Mammalian dose elimination route and rate

Health issues

Specific human health issues (hazard-based)

Carcinogen

Genotoxic

Endocrine disruptor

No data found

; ; ; ;

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

May cause respiratory problems

Handling issues

Property

Value and interpretation

General

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

CLP classification 2013

Health: H315, H319, H335

WHO Classification

Not listed (Not listed)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

Limited shelf life. Store at -20 DegC

TRANSLATIONS

Language

Name

English

indolylacetic acid

French

AIA

German

Danish

Italian

Spanish

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	28/11/2025
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

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