Pyrithiobac-sodium is a post-emergence herbicide. It has a high aqueous solubility, is semi-volatile and, based on its chemical properties, it is very mobile and has high potential to leach to groundwater. It is generally moderately persistent in soil systems but tends to be non-persistent in aquatic systems. It has a low mammalian toxicity but may bioaccumulate. It shows a low to moderate level of toxicity to most biodiversity.
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.
Example manufacturers & suppliers of products using this active now or historically
DuPont
Kumiai Chemical Industry Co. Ltd.
Example products using this active
Stap
Staple
Staple LX
Formulation and application details
Usually supplied as a soluble powder
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
728000
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
High
Solubility - In organic solvents at 20 °C (mg l⁻¹)
812
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
Acetone
-
270000
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
Methanol
-
10
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
n-Hexane
-
205
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
Ethyl acetate
-
Melting point (°C)
234
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
-
Boiling point (°C)
-
-
-
Degradation point (°C)
234
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
-
Flashpoint (°C)
-
-
-
Octanol-water partition coefficient at pH 7, 20 °C
P
1.45 X 10-01
Calculated
-
Log P
-0.84
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
Low
Fat solubility of residues
Solubility
-
-
-
Data type
-
-
-
Density (g ml⁻¹)
1.61
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
-
Dissociation constant pKa) at 25 °C
2.34
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
-
Strong acid
Vapour pressure at 20 °C (mPa)
4.80 X 10-06
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)
-
-
-
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)
60
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
Moderately persistent
DT₅₀ (lab at 20 °C)
-
-
-
DT₅₀ (field)
-
-
-
DT₉₀ (lab at 20 °C)
-
-
-
DT₉₀ (field)
-
-
-
DT₅₀ modelling endpoint
-
-
-
Note
General literature data states DT₅₀ 60 days in silty soil. DT₅₀ 10 days for uplands and flooded soil. Main degradation route is microbial.
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
13
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
Moderately fast
Note
pH sensitive: DT₅₀ 11 days at pH 5, 15 days at pH 9, all at 25 °C
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
Stable
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
Stable
Note
-
Water-sediment DT₅₀ (days)
-
-
-
Water 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)
0.5
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
-
Koc (mL g⁻¹)
-
Notes and range
General literature data gives Kd values ranging from 0.32 (sandy loam) to 0.75 (silty loam). Peered review study - Kd 0.22 to 0.59 L/kg
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
-
-
-
SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate
Value
Cannot be calculated
-
-
Note
-
Potential for particle bound transport index
-
-
-
Potential for loss via drain flow
-
-
-
Photochemical oxidative DT₅₀ (hrs) as indicator of long-range air transport risk
-
-
-
Bio-concentration factor
BCF (l kg⁻¹)
Low risk
Q3 Q = Miscellaneous data from online sources 3 = Unverified data of known source
Based on LogP < 3
Low risk
CT₅₀ (days)
-
-
Known metabolites
None
ECOTOXICOLOGY
Terrestrial ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
3200
L3 L = Pesticide manuals and hard copy reference books / other sources 3 = Unverified data of known source
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
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