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Pesticides: toxicity

Any chemical substance is toxic if it is ingested or absorbed in excessive amounts. Table salt, for example, if consumed in excess, can be toxic. The degree of danger or hazard when using a pesticide is determined by multiplying toxicity times exposure.

The designation given to a pesticide indicating its relative level of toxicity is called the Lethal Dose, or LD 50 value. This value identifies the dosage rate necessary to kill 50 percent of a test population. Lethal dose is expressed in milligrams of chemical per kilogram of body weight of the test population. The lower the LD 50 number, the more toxic the material. The toxicity rating is important as an indicator, but the length of exposure, type of exposure and other factors also impact the relative hazard of any pesticide.

Signal words written on every label indicate a pesticide's degree of toxicity. Every pesticide label contains valuable information you should read and understand before using the product. The law requires you to follow label instructions, and following the instructions will provide the best results for your garden and minimize risk to you.


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Updated Tuesday, July 22, 2014