Siduron is a selective pre-emergence herbicide. It has a moderate aqueous solubility, is volatile and, based on its chemical properties, it is moderately mobile with has a high potential to leach to groundwater. It is persistent in both soil and water systems. It has a relatively low mammalian toxicity and would not be expected to bioaccumulate. It is classified as an irritant. It is not highly toxic to birds, is moderately toxic to fish, algae and honeybees.
Hazard 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. These hazard alerts do not take account of usage patterns or exposure, thus do not represent risk.
Environmental fate
Ecotoxicity
Human health
Environmental fate Moderate alert: Moderately persistent; GUS: Transition state; Drainflow: Moderately mobile; Potential for particle bound transport: Medium
Golf courses; Sports fields; Sod farms and grass seed production; Roadsides; Parks
Efficacy & activity
-
GB regulatory status
GB COPR regulatory status
Not approved
Date COPR inclusion expires
Not applicable
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
Not applicable
Date EC 1107/2009 inclusion expires
Not applicable
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
Australia
Chemical structure
Isomerism
Siduron exhibits stereoisomerism, specifically cis-trans isomerism, due to the presence of a substituted cyclohexyl ring in its molecular structure. The molecule contains a chiral centre at the 2-position of the cyclohexyl group, which allows for the formation of cis- and trans-isomers depending on the spatial arrangement of substituents around the ring. Commercial formulations of siduron typically consist of a mixture of these isomers, rather than a single pure form.
Selective, absorbed by roots and translocated. Photosynthetic electron transport inhibitor at the photosystem II.
CAS RN
1982-49-6
EC number
217-844-2
CIPAC number
321
US EPA chemical code
035509
PubChem CID
16116
CLP index number
No data found
Molecular mass
232.32
PIN (Preferred Identification Name)
N-(2-methylcyclohexyl)-N'-phenylurea
IUPAC name
1-(2-methylcyclohexyl)-3-phenylurea
CAS name
N-(2-methylcyclohexyl)-N'-phenylurea
Forever chemical
-
Other status information
-
Relevant Environmental Water Quality Standards
-
Herbicide Resistance Class (HRAC MoA class)
C2
Herbicide Resistance Class (WSSA MoA class)
7
Insecticide Resistance Class (IRAC MoA class)
Not applicable
Fungicide Resistance Class (FRAC MOA class)
Not applicable
Examples of recorded resistance
-
Physical state
Colourless, odourless crystals
Commercial
Property
Value
Availability status
Current
Introduction & key dates
1994, introduced; 2020, discontinued USA
Example manufacturers & suppliers of products using this active now or historically
Gowan Co.
Raschig
Example products using this active
Tupersan
Formulation and application details
Usually formulated as a wettable powder and applied as a pre-emergence treatment to bare soil. It may also be formulated as a mixture with fertilisers.
Commercial production
The production of siduron typically begins with the synthesis of N,N-dimethylurea, which serves as a key intermediate. This compound is then reacted with 2,3-dihydro-1H-indene-1-carbonyl chloride or a similar indanone derivative under controlled conditions to form the final siduron molecule. The reaction involves nucleophilic substitution, where the urea nitrogen attacks the carbonyl carbon of the acid chloride, forming the desired urea linkage. The process may require solvent mediation and temperature control to optimise yield and purity.
Impact on climate of production and use
Data for the amount of life cycle GHGs produced by siduron are not available in the public domain. However, whilst estimates vary, more general data suggests that between 18 and 27 kilograms of CO₂e is emitted per kilogram of herbicide produced.
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
Low volatility
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
6.80 X 10-06
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
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)
-
-
-
Degradation
Property
Value
Source; quality score; and other information
Interpretation
General biodegradability
-
Soil degradation (days) (aerobic)
DT₅₀ (typical)
135
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
Persistent
DT₅₀ (lab at 20 °C)
90
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment ) 3 = Unverified data of known source
Moderately persistent
DT₅₀ (field)
-
-
-
DT₉₀ (lab at 20 °C)
-
-
-
DT₉₀ (field)
-
-
-
DT₅₀ modelling endpoint
-
-
-
Note
Best available data
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
290
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
Stable
Note
-
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
Stable
W4 W = French database provided by ARVALIS-Institut du Végétal. Dataset no longer available. 4 = Verified data
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
Kd (mL g⁻¹)
-
H3 H = The US ARS pesticide properties database. Dataset is no longer available. 3 = Unverified data of known source
Moderately mobile
Koc (mL g⁻¹)
420
Notes and range
-
Freundlich
Kf (mL g⁻¹)
-
-
-
Kfoc (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
2.69
Calculated
Transition state
SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate
Value
2.11 X 10-01
Calculated
-
Note
-
Potential for particle bound transport index
Medium
Calculated
-
Potential for loss via drain flow
Moderately mobile
Calculated
-
Photochemical oxidative DT₅₀ (hrs) as indicator of long-range air transport risk
-
-
-
Bio-concentration factor
BCF (l kg⁻¹)
84
Q2 Q = Miscellaneous data from online sources 2 = Unverified data of unknown source
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
Environmental fate
Human health
Warning:
