| Potassium hydrogen phosphonate |

Last updated: 19/02/2026
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(Also known as: monopotassium phosphite; monopotassium phosphonate) |
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 |
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An inorganic potassium salt that has fungicidal properties and used to control Pythium and Phytophthora on a variety of fruit and ornamental crops. It is usually used in a reaction mixture with dipotassium phosphonate. |
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Root rot (Pythium spp.); Root and stem rots (Phytophthora spp.) |
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Fruit including avocados, apples, grapes; Ornamentals; Trees |
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- |
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- |
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- |
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Approved (as potassium phosphonates) |
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30/09/2026 |
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Crop over 5m - See Authorisation for Crop LERAP Details |
| EC Regulation 1107/2009 (repealing 91/414) |
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Approved (as potassium phosphonates) |
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France |
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31/01/2026 |
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No |
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Yes |
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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 |
| ✓ |
  |
✓ |
✓ |
✓ |
✓ |
✓ |
✓ |
✓ |
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ISIceland |
NONorway |
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|   |
  |
  |
  |
  |
  |
  |
  |
  |
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None |
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H₂KO₃P |
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OP(O)[O-].[K+] |
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- |
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BZHCGFBZBPVRFE-UHFFFAOYSA-N |
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InChI=1S/K.H2O3P/c;1-4(2)3/h;1-2H/q+1;-1 |
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Yes |
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Fungicide |
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Inorganic compound |
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- |
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- |
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Natural |
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Mixed mode of application including direct toxicity to plant pathogens reducing populations and promotion of plants natural defences |
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Phosphonates occur naturally in biological cells |
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Crop protection |
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Pythium spp.; Phytophthora spp. including root rot |
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Fruit including avocados, apples, grapes; Ornamentals; Trees |
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- |
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13977-65-6 |
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604-162-9 |
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756 |
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076416 |
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23701737 |
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No data found |
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120.09 |
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- |
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potassium hydrogen phosphonate |
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potassium dihydrogen phosphite |
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| UK Poisons List Order 1972 |
Rotterdam Convention |
Montreal Protocol |
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| Stockholm Convention |
OSPAR |
EU Water Framework Directive |
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- |
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- |
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- |
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Yes [ R11 Rule 11: Pesticide active ingredients that are environmentally persistent (where sediment phase only DT₅₀ => 90 days or water phase only DT₅₀ => 90 days or DT₅₀ (field) => 60 days (note lab values are used when field values are not available)) ] |
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- |
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Not applicable |
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Not applicable |
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Not applicable |
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NC |
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- |
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Deliquescent solid |
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Current |
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1997, introduced USA |
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- Luxembourg Industries (Pamol) Ltd
- UIM Agrochemicals (Australia)
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Usually supplied as an aqueous solution with a variety of application methods used including foliar sprays, soil drenches and root dips |
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There are various commercial production methods including; (1) from phosphonic acid, (2) using the Michaelis–Arbuzov reaction, and (3) from phosphorus trichloride |
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- |
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500000 |
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High |
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- |
- |
- |
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73 |
(as potassium phosphonates) |
- |
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Decomposes before boiling |
(as potassium phosphonates) |
- |
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180 |
(as potassium phosphonates) |
- |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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1.65 |
(as potassium phosphonates) |
- |
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2.0 |
(as potassium phosphonates) |
- |
| PKa(2) = 6.59 |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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- |
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142 |
(as potassium phosphonates) |
Persistent |
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142 |
as phosphonic acid |
Persistent |
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- |
- |
- |
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381 |
as phosphonic acid |
Very persistent |
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- |
- |
- |
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- |
- |
- |
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EU dossier lab studies for phosphonic acid DT₅₀ range 88-196 days, DT₉₀ range 319-442 days |
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- |
- |
- |
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- |
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- |
- |
- |
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- |
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- |
- |
- |
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- |
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- |
- |
- |
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- |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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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. |
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- |
| Soil adsorption and mobility |
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10.7 |
as phosphonic acid |
Moderately mobile |
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453.6 |
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EU dossier Kd range 3.1-18.96 mL g⁻¹, Koc range 228-972 mL g⁻¹, Soils=5 |
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- |
- |
- |
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- |
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- |
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- |
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- |
| Known soil and groundwater metabolites |
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None
| Terrestrial ecotoxicology |
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> 5000 |
Rat |
Low |
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- |
- |
- |
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- |
- |
- |
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> 2250 |
Colinus virginianus as phosphonic acid |
Low |
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> 1335 |
Colinus virginianus as phosphonic acid |
- |
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149.04 |
Colinus virginianus NOEC as phosphonic acid |
Moderate |
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> 1000 |
Eisenia foetida as phosphonic acid |
Low |
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182.5 |
Eisenia foetida as phosphonic acid |
Low |
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Nitrogen mineralisation: Minor transient effects Carbon mineralisation: Minor transient effects |
Dose: up to 26.99 mg posphonic acid/kg soil 28 Day |
- |
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- |
- |
- |
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- |
- |
- |
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10100 |
6 plant species tested |
- |
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- |
- |
- |
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- |
- |
- |
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> 145 |
as potassium phosphonates |
Low |
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- |
- |
- |
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- |
- |
- |
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- |
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- |
- |
- |
| - |
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- |
- |
- |
| - |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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- |
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- |
- |
- |
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- |
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- |
- |
- |
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- |
- |
- |
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> 20200 |
Aphidius rhopalosiphi as phosphonic acid |
Low |
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> 8080 |
Typhlodromus pyri as phosphonic acid |
Low |
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- |
- |
- |
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- |
- |
- |
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- |
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- |
- |
- |
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- |
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> 118 |
Oncorhynchus mykiss as phosphonic acid |
Low |
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100 |
Oncorhynchus mykiss as phosphonic acid |
Low |
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- |
- |
- |
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> 118 |
Daphnia magna as phosphonic acid |
Low |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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100 |
Chironomus riparius as phosphonic acid |
Low |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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146.7 |
Desmodesmus subspicatus as phosphonic acid |
Low |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
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- |
- |
- |
| Regulatory Threshold Levels (RTLs) used to calculate Total Applied Toxicity (TAT) |
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500 |
Worst case of acute and chronic mammals |
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29.808 |
Worst case of acute and chronic birds |
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36.5 |
Worst case of acute and chronic earthworms |
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2020 |
Worst case of non-target plants vegetative vigour and seedling emergence |
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2.9 |
Worst case of contact and oral honeybees |
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4040 |
Worst case of parasitic wasps and predatory mites |
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1.18 |
Worst case of temperate acute and chronic fish |
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1.18 |
Worst case of temperate acute and chronic aquatic invertebrates |
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14.67 |
Worst case of free-floating plants, rooted plants, acute and chronic algae |
| HUMAN HEALTH AND PROTECTION |
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High (class III) |
- |
- |
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> 5000 |
Rat |
Low |
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- |
- |
- |
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- |
- |
- |
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> 4000 |
Rat |
- |
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> 5.05 |
Rat |
- |
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- |
- |
- |
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3.9 |
as phosphonic acid |
- |
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None allocated |
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- |
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None allocated |
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- |
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None allocated |
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- |
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100 |
default |
- |
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- |
- |
- |
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Negligible risks identified for proposed uses |
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Negligible risks identified for proposed uses |
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- |
- |
- |
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| Carcinogen |
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Endocrine disruptor |
XNo, known not to cause a problem |
A0 A = Chromosome aberration (EFSA database) 0 = No data ; 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 |
XNo, known not to cause a problem |
| Reproduction / development effects |
Acetyl cholinesterase inhibitor |
Neurotoxicant |
?Possibly, status not identified |
XNo, known not to cause a problem |
No data found |
| Respiratory tract irritant |
Skin irritant |
Skin sensitiser |
| No data found |
XNo, known not to cause a problem |
XNo, known not to cause a problem |
| Eye irritant |
Phototoxicant |
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XNo, known not to cause a problem |
No data found |
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No further information available |
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Not oxisiding or explosive Not expected to auto-ignite; Not highly flammable |
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Not classified |
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Not listed (Not listed) |
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- |
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- |
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- |
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potassium hydrogen phosphonate |
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- |
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- |
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- |
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- |
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- |
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- |
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- |
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- |
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- |
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- |
| Record last updated: |
19/02/2026 |
| 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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