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04-21-09 How toxic are fertilizers?

How toxic are fertilizers?

Planting season is upon us and therefore many homeowners are purchasing and using fertilizers. Household fertilizers typically contain nitrogen, phosphoric acid (phosphorus) and potash (potassium). Frequently, fertilizers are described by the initials NPK, which represent the content of nitrogen, phosphorus and potassium respectively or may be described by a set of 3 numbers, i.e. 10-5-4, which represent the percentages of NPK by weight.

Fertilizers in general are considered to have a low degree of toxicity although after oral ingestions they may cause mild GI upset with nausea, vomiting and diarrhea. Because of the nitrate content in them, methemoglobinemia may occur in susceptible individuals with sufficient oral dose. Also, certain fertilizers may be mixed with various pesticides (herbicides, insecticides, etc) which may cause their own types of toxicity. These exposures need to be evaluated on a case by case basis as the amount ingested (or other route of exposure) and the particular additive in the product will determine the likelihood of toxic effects.

Question prepared by: John G. Benitez, MD, MPH Medical Toxicologist