Signal Words

Acute toxicities are the basis for assigning pesticides to a toxicity category and selecting the appropriate signal word for the product label. Pesticides that are classified as "highly toxic" on the basis of either oral, dermal, or inhalation toxicity must have the signal words DANGER and POISON (in red letters) and a graphic of a skull and crossbones prominently displayed on the package label. PELIGRO, the Spanish word for danger, must also appear on the label of highly toxic chemicals. Acute oral LD₅₀ values for pesticide products in this group range from a trace amount to 50 mg/kg. An exposure of a few drops of a highly toxic material taken orally could be fatal to a 150-pound person.

Some pesticide products are labeled with the signal word DANGER without the skull and crossbones symbol. A DANGER signal word does not provide information about the LD₅₀ value of the chemical. Instead, this signal word alerts the user of potentially more severe skin or eye effects from the product (caused by its irritant or corrosive properties).

Pesticide products considered "moderately toxic" must have the signal words WARNING and AVISO (Spanish) displayed on the label. Acute oral LD₅₀ values range from 50 to 500 mg/kg. An exposure of 1 teaspoon to 1 ounce could be fatal to a 150-pound person. Pesticide products classified as either "slightly toxic" or "relatively nontoxic" are required to have the signal word CAUTION on the pesticide label. Acute oral LD₅₀ values are greater than 500 mg/kg.