Formaldehyde

Formaldehyde	Last updated: 20/08/2025
(Also known as: formalin; methanal; methyl aldehyde; methylene oxide; paraformaldehyde)

SUMMARY

Formaldehyde tends to be used as a disinfectant for soil, equipment, yards etc. but also has some fungicidal activity. It is highly toxic and highly volatile. Risk of drift is a concern. It is not persistent in soil systems and the potential for leaching to groundwater is low. It is highly toxic to mammals, a recognised carcinogen and severe irritant. It may also cause genetic defects. It is moderately toxic to most biodiversity species.

GENERAL INFORMATION

Description

Used as a disinfectant for soil, equipment, yards etc. Also used as an animal husbandry fungicide. Can also be a pesticide transformation product

Examples of veterinary uses

Examples of species treated

Approval status

VMR 2013/2033 approval status (GB/UK)

EU Regulatory approval status

Chemical structure

Isomerism

None

Chemical formula

CH₂O

Canonical SMILES

C=O

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

WSFSSNUMVMOOMR-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/CH2O/c1-2/h1H2

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
formaldehyde	-

General status

Veterinary substance type

Metabolite Type

Soil; Surface water

Other bioactivity & uses

Inert solvent; Bactericide; Biocide; Disinfectant; Algicide; Slimicide

Substance groups

Unclassified gas

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Acts by protein denaturation

Molecular targets

CAS RN

50-00-0

EC number

200-001-8

CIPAC number

156

US EPA chemical code

043001

PubChem CID

712

CLP index number

605-001-00-5

Therapeutic Class

ATCvet Code

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

30.03

PIN (Preferred Identification Name)

IUPAC name

formaldehyde

CAS name

formaldehyde

Forever chemical

Other status information

Listed on USA Toxic Release Inventory; Subject to the provisions of the UK Poisons Act 1972; Some applications may be approved under the GB Biocide Products Regulations

Relevant Environmental Water Quality Standards

UK Environment Agency non-statutory standard for the protection of aquatic life in fresh surface water: 5 µg l⁻¹ as annual average, 50 µg l⁻¹ as max acceptable conc.

Physical state

Gas

Can be a metabolite of:

Parent

Formation medium

Estimated maximum occurrence fraction

1107/2009 relevancy

trioxymethylene

Acid soil

Major fraction

bronopol

Soil

dazomet

Soil

0.205

Major fraction

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1888, introduced

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

Example products using this active

Formalin Fungicide

Formulation and application details

Often used as a dip, drench or spray treatment. May also be used as a fumigant to sterilise animal houses.

Commercial production

Formaldehyde is primarily manufactured through the catalytic oxidation of methanol, a process that is both efficient and scalable. First, high-purity methanol is vaporised and mixed with air. This mixture is then passed over a catalyst, either silver (in the older “S” process) or metal oxides like iron-molybdenum (in the more modern “MO” process), at temperatures between 300–600 DegC. The reaction produces formaldehyde gas and water vapor. The resulting gas is cooled and absorbed into water to form a formalin solution (typically 37–55% formaldehyde), which is stabilized with methanol to prevent polymerisation.

Impact on climate of production and use

Nicholson et al. (2023) report that the manufacturing and transport of 1 kg of formaldehyde produces approximately 0.8 kg of CO₂e

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

550000

High

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

Miscible

Acetone

Melting point (°C)

-92

Boiling point (°C)

-19.2

Degradation point (°C)

Flashpoint (°C)

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

2.24 X 10⁰⁰

Calculated

Log P

0.35

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

0.82

Dissociation constant pKa) at 25 °C

13.27

Strong base

Vapour pressure at 20 °C (mPa)

53300000

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)

3.41 X 10^-02

Non-volatile

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)

Refractive Index

Environmental release

Degradation

Property

Value

Source; quality score; and other information

Interpretation

Soil degradation (days) (aerobic)

DT₅₀ (typical)

Non-persistent

DT₅₀ (lab at 20 °C)

1.9

Non-persistent

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

Other sources: DT₅₀ 2-20 days

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Note

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)

Mobile

K_oc (mL g⁻¹)

Notes and range

Other sources: DT₅₀ 2-20 days

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

0.68

Calculated

Low leachability

Bio-concentration factor

BCF (l kg⁻¹)

0.2

Low potential

CT₅₀ (days)

Not available

Known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 550

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Unknown species

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

> 5000

Anas platyrhynchos

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

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

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

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

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)

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

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

> 1.84

Oncorhynchus mykiss

Moderate

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

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

41.0

Danio rerio

Moderate

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

> 0.43

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)

> 11.4

Ceriodaphnia dubia

Moderate

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)

> 0.88

Unknown species

Moderate

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

> 0.10

Phyllospora comosa

Moderate

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)

> 550

Rat

Moderate

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

270

Rabbit

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 0.6

Rat 4 hr

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

Most probable exposure route is via inhalation

Occupational

Most probable exposure route is via inhalation - PPE/PPC essential

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

Eye irritant

Phototoxicant

No data found

General human health issues

IARC Group 1 carcinogen, UK HSE - carcinogen; CLP data - known human carcinogen; US NTP - known carcinogen; OSHA - known human carcinogen; US EPA - probable human carcinogen
Severe obstructive tracheobronchitis may result from inhalation causing throat spasms and a build up of fluid in the lungs, leading to death
Suspected of causing genetic defects
May cause serious damage of the gastrointestinal tract

Handling issues

Property

Value and interpretation

General

Flammable gas
Reacts explosively with peroxides and performic acid
IMDG Tranport Class 3

CLP classification 2013

Health: H301, H311, H314, H317, H331, H341, H350

WHO Classification

Not classified: Fumigant (Not classified: Fumigant)

UN Number

UN1198

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

formaldehyde

French

formaldehyde

German

Formaldehyd

Danish

formaldehyd

Italian

formaldeide

Spanish

formaldehído

Greek

Polish

formaldehyd

Swedish

Hungarian

Dutch

formaldehyde

Norwegian

Record last updated:	20/08/2025
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