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 necessary to kill
50 percent of a test population. The lethal dose is expressed in milligrams of chemi-
cal per kilogram of body weight of the test population. The lower the LD 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. The toxicity of pesticides is often measured using an LD 50 (lethal
dose) or an LC 50 (lethal concentration). Both the LD 50 and LC 50 measure only acute
effects and therefore provide no information about a chemical’s connection to long-
term health issues.^36
The tests for acute and chronic toxicity are the only science-based methods cur-
rently used to predict risks to users and consumers. But they have limitations. These
tests are usually done on rodents, which may not always accurately predict effects on
humans. Plus, they do not take into consideration possible interactions and conse-
quences of several compounds acting together.
All labels include the warning, ‘‘Keep out of reach of children.’’ In addition, most
labels include ‘‘signal words’’ which give an indication of the pesticide’s toxicity or
corrosiveness. These signal words are relative terms. They indicate how pesticides
compare to one another. Even if a pesticide is considered to be relatively low in toxic-
ity, it can be a deadly poison at a fairly low dose.^37Inert IngredientsPesticide products contain both ‘‘active’’ and ‘‘inert’’ ingredients. These terms have
been defined by a federal law, the Federal Insecticide, Fungicide, and Rodenticide Act
(FIFRA) of 1947. An active ingredient is one that prevents, destroys, repels, or miti-
gates a pest, or is a plant regulator, defoliant, desiccant, or nitrogen stabilizer. By law,
the active ingredient must be identified by name on the label together with its per-
centage by weight. An inert ingredient is simply an ingredient in the product that is
not intended to affect a target pest. For example, isopropyl alcohol may be an active
ingredient and antimicrobial pesticide in some products; however, in other products,
it functions as a solvent and may be considered inert. The law does not require inert
ingredients to be identified by name and percentage on labels, but the total percent-
age of such ingredients must be declared.^38Inert Name ChangeIn September 1997, the EPA issued a regulation notice to encourage manufac-
turers, formulators, producers, and registrants of pesticide products to voluntarily
substitute the term ‘‘other ingredients’’ as a heading for the ‘‘inert’’ ingredients in the
ingredient statement on pesticide labels. The EPA made this change after learning the
results of a consumer survey on the use of household pesticides. Many comments
from the public and the consumer interviews prompted the EPA to discontinue the
use of the term ‘‘inert.’’ Many consumers are misled by the term ‘‘inert ingredient,’’8 | Pesticides