(Also known as: alachlore; acetanilide; methachlor; metachlor; CDMA)
SUMMARY
Alachlor is a pre-emergence chloroacetanilide herbicide. It is moderately soluble in water, quite volatile and is not expected to readily leach to groundwater. It tends not to persist in either soil or water systems. It has a moderate mammalian toxicity and a low potential for bioaccumulation. Alachlor is moderately toxic to birds, most aquatic organisms, honeybees and earthworms.
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: Drainflow: Moderately mobile; Potential for particle bound transport: Medium
WFD priority substance; OSPAR candidate; Potential groundwater contaminant; Chemical subject to PIC regulations; PAN Bad Actor
Relevant Environmental Water Quality Standards
EU Directive 2008/105/EC EQS surface waters: annual average 0.3 µg l⁻¹; max measured 0.7 µg l⁻¹
Herbicide Resistance Class (HRAC MoA class)
K3
Herbicide Resistance Class (WSSA MoA class)
15
Insecticide Resistance Class (IRAC MoA class)
Not applicable
Fungicide Resistance Class (FRAC MOA class)
Not applicable
Examples of recorded resistance
-
Physical state
Colourless/yellow crystals
Formulations
Property
Value
Example manufacturers & suppliers of products using this active now or historically
Monsanto
Makhteshim-Agan
Pillar International
Example products using this active
Lasso
Alanex
Pillarzo
Bullet
Cannon
Bronco
Formulation and application details
Usually supplied as emulsifiable concentrates, microscopic capsules and granules
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
240
B5 B = UK CRD and ACP Evaluation Documents / and other DEFRA (UK) documents; Also Chemicals Regulation Division, Health and Safety Executive (HSE), UK (click here ) 5 = Verified data used for regulatory purposes
Moderate
Solubility - In organic solvents at 20 °C (mg l⁻¹)
-
-
-
Melting point (°C)
41
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
-
Boiling point (°C)
100
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID ) 3 = Unverified data of known source
-
Degradation point (°C)
105
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
-
Flashpoint (°C)
137
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
(closed cup)
-
Octanol-water partition coefficient at pH 7, 20 °C
P
1.23 X 1003
Calculated
-
Log P
3.09
B5 B = UK CRD and ACP Evaluation Documents / and other DEFRA (UK) documents; Also Chemicals Regulation Division, Health and Safety Executive (HSE), UK (click here ) 5 = Verified data used for regulatory purposes
High
Fat solubility of residues
Solubility
-
-
-
Data type
-
-
-
Density (g ml⁻¹)
1.13
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
-
Dissociation constant pKa) at 25 °C
0.62
Q3 Q = Miscellaneous data from online sources 3 = Unverified data of known source
-
Strong acid
Vapour pressure at 20 °C (mPa)
2.9
B5 B = UK CRD and ACP Evaluation Documents / and other DEFRA (UK) documents; Also Chemicals Regulation Division, Health and Safety Executive (HSE), UK (click here ) 5 = Verified data used for regulatory purposes
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)
3.20 X 10-03
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)
14
B5 B = UK CRD and ACP Evaluation Documents / and other DEFRA (UK) documents; Also Chemicals Regulation Division, Health and Safety Executive (HSE), UK (click here ) 5 = Verified data used for regulatory purposes
Non-persistent
DT₅₀ (lab at 20 °C)
35
Q2 Q = Miscellaneous data from online sources 2 = Unverified data of unknown source
Moderately persistent
DT₅₀ (field)
14
B4 B = UK CRD and ACP Evaluation Documents / and other DEFRA (UK) documents; Also Chemicals Regulation Division, Health and Safety Executive (HSE), UK (click here ) 4 = Verified data
Non-persistent
DT₉₀ (lab at 20 °C)
-
-
-
DT₉₀ (field)
-
-
-
DT₅₀ modelling endpoint
-
-
-
Note
Field studies DT₅₀ range 1-3 weeks; Other sources: DT₅₀ 80 days (R2)
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
0.5
K3 K = Research datasets (e.g. Pandora, Demetra; these datasets no longer available). Norman Ecotoxicology database. (click here ) 3 = Unverified data of known source
Fast
Note
Stable to UV light
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
0.5
B5 B = UK CRD and ACP Evaluation Documents / and other DEFRA (UK) documents; Also Chemicals Regulation Division, Health and Safety Executive (HSE), UK (click here ) 5 = Verified data used for regulatory purposes
Non-persistent
Note
-
Water-sediment DT₅₀ (days)
2
B4 B = UK CRD and ACP Evaluation Documents / and other DEFRA (UK) documents; Also Chemicals Regulation Division, Health and Safety Executive (HSE), UK (click here ) 4 = Verified data
Fast
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)
-
R3 R = Peer reviewed scientific publications 3 = Unverified data of known source
Moderately mobile
Koc (mL g⁻¹)
335
Notes and range
-
Freundlich
Kf (mL g⁻¹)
16.5
R4 R = Peer reviewed scientific publications 4 = Verified data
Slightly mobile
Kfoc (mL g⁻¹)
1994
1/n
0.81
Notes and range
Literature values: Kf range 11.8-20.5 mL g⁻¹; Kfoc range 339-4214 mL g⁻¹, 1/n range 0.70-0.91, Soils = 5
pH sensitivity
-
Fate indices
Property
Value
Source; quality score; and other information
Interpretation
GUS leaching potential index
0.80
Calculated
Low leachability
SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate
Value
1.31 X 10-02
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)
39
P4 P = Other non-EU, UK or US Governments and Regulators 4 = Verified data
B5 B = UK CRD and ACP Evaluation Documents / and other DEFRA (UK) documents; Also Chemicals Regulation Division, Health and Safety Executive (HSE), UK (click here ) 5 = Verified data used for regulatory purposes
Rat
High
(ppm diet)
200
-
Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)
-
-
-
Birds - Acute LD₅₀ (mg kg⁻¹)
1536
B5 B = UK CRD and ACP Evaluation Documents / and other DEFRA (UK) documents; Also Chemicals Regulation Division, Health and Safety Executive (HSE), UK (click here ) 5 = Verified data used for regulatory purposes
Colinus virginianus
Moderate
Birds - Short term dietary (LC₅₀/LD₅₀)
-
-
-
Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)
-
-
-
Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)
386.8
B5 B = UK CRD and ACP Evaluation Documents / and other DEFRA (UK) documents; Also Chemicals Regulation Division, Health and Safety Executive (HSE), UK (click here ) 5 = Verified data used for regulatory purposes
Moderate
Earthworms - Chronic NOEC, reproduction (mg kg⁻¹)
-
-
-
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)
16
K4 K = Research datasets (e.g. Pandora, Demetra; these datasets no longer available). Norman Ecotoxicology database. (click here ) 4 = Verified data
Moderate
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)
1.8
B5 B = UK CRD and ACP Evaluation Documents / and other DEFRA (UK) documents; Also Chemicals Regulation Division, Health and Safety Executive (HSE), UK (click here ) 5 = Verified data used for regulatory purposes
Oncorhynchus mykiss
Moderate
Temperate Freshwater Fish - Chronic 21 day NOEC (mg l⁻¹)
0.19
P3 P = Other non-EU, UK or US Governments and Regulators 3 = Unverified data of known source
Unknown species
Moderate
Tropical Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
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
Low risk to Europeans as no longer approved for use
Occupational
Occupational exposure may occur through inhalation and dermal contact
MRLs
European
EU MRL pesticide database
Great Britain
GB MRL Register
Notes
-
Drinking Water Standards
Non-statutory WHO drinking water guideline 0.02 mg l⁻¹
B5 B = UK CRD and ACP Evaluation Documents / and other DEFRA (UK) documents; Also Chemicals Regulation Division, Health and Safety Executive (HSE), UK (click here ) 5 = Verified data used for regulatory purposes
UK EA QS database 2018
-
Drinking Water MAC (μg l⁻¹)
-
-
-
Mammalian dose elimination route and rate
-
-
-
Health issues
Specific human health issues
Carcinogen
Genotoxic
Endocrine disruptor
?Possibly, status not identified
A3 A = Chromosome aberration (EFSA database) 3 = Negative
;
B0 B = DNA damage/repair (EFSA database) 0 = No data
;
C0 C = Gene mutation (EFSA database) 0 = No data
;
D0 D = Genome mutation (EFSA database) 0 = No data
;
E3 E = Unspecified genotoxicity type (miscellaneous data source) 3 = Negative
?Possibly, status not identified
Reproduction / development effects
Acetyl cholinesterase inhibitor
Neurotoxicant
?Possibly, status not identified
XNo, known not to cause a problem
XNo, known not to cause a problem
Respiratory tract irritant
Skin irritant
Skin sensitiser
XNo, known not to cause a problem
?Possibly, status not identified
?Possibly, status not identified
Eye irritant
Phototoxicant
✓Yes, known to cause a problem
No data found
General human health issues
US Toxics Release Inventory (TRI) Program listed carcinogen; CLP data - suspected carcinogen; US EPA - likely to be a human carcinogen at high doses Probable lung and kidney toxicant Causes irreversible eye damage Possibly genotoxic Endocrine issues - Competitive binding to estrogen and progesterone receptors
Handling issues
Property
Value and interpretation
General
Corrosive IMDG Transport Hazard Class 9
CLP classification 2013
Health: H302, H317, H351 Environment: H400, H410
WHO Classification
II (Moderately hazardous)
UN Number
UN3077
Waste disposal & packaging
Packaging Group III (minor danger)
Shelf-life, storage, stability and reactivity
Chemically stable under standard ambient conditions
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
