Potassium monophosphate, also known as potassium dihydrogen phosphate, is a crystalline powder used as a pesticide and fertilizer for fruits, vegetables and flowers. The Environmental Protection Agency, EPA, approves the use of potassium monophosphate on apples, grapes, cucumbers, melons, summer and winter squash, watermelons, mangoes, peaches, peppers, plums, cherries, tomatoes and roses to control the growth of powdery mildew. Testing of potassium monophosphate shows low toxicity, making it a low risk for dangerous effects to humans and the environment.
Toxicology
The EPA performed required mammalian toxicology testing and found that the acute oral median lethal dose, noted as LD50, for rats is greater than 500 mg/kg and the acute skin lethal dose for rabbits is greater than 2,000 mg/kg. Because of the low toxicity level, the EPA concluded that tests to determine the ability of potassium monophosphate to cause mutations or interfere with development do not need to be completed.
Skin Irritation
Potassium monophosphate poses little risk for skin irritation. The EPA lists this compound in toxicology category IV, labeling it as a non-irritant. However, take caution not to get potassium monophosphate in your eyes, because it can cause mild eye irritation.
Water Contamination
Potassium monophosphate exists as a compound in nature. When used as a fertilizer and pesticide, the plants absorb most of the potassium monophosphate. This means runoff from rainfall into ground water sources, including drinking water, rarely occurs. Testing of the water sources in areas that use potassium monophosphate shows that residues of the compound do not significantly increase levels above naturally occurring levels. The health risk for humans drinking contaminated water from areas that utilize potassium monophosphate remains negligible.
Ecological Dangers
Because of the low toxicity level for mammals, including humans, exposed to potassium monophosphate, the danger to plants and other types of animals living in the treated areas is minimal. The EPA reports that tests on non-target species like insects, fish and birds confirm the compound is practically non-toxic. Potassium monophosphate poses the highest danger for aquatic invertebrates, like sponges, worms, crustaceans and mullosks, which show the compound to be slightly toxic.
Caution
Although labeled as non-toxic and safe for human use and consumption when used as a fertilizer and pesticide, the EPA says you should never dispose of potassium monophosphate directly into water or in areas with surface water present.
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