or toxic if absorbed in excessive amounts. Pesticides can cause skin or eye damage
(topical effects) and also induce allergic responses. However, if used according to
labelled directions and with the proper personal protective equipment (PPE), pesti-
cides can be used safely. For this reason, people who use pesticides or regularly come
in contact with them must understand the relative toxicity and the potential health
effects of the products they use. The risk of exposure to pesticides can be illustrated
with the following simple equation:
Hazard of Pesticide Use¼ToxicityActual ExposureToxicity is a measure of the ability of a pesticide to cause injury, which is a prop-
erty of the chemical itself. Pesticide toxicity is determined by exposing test animals
(usually rats, mice, rabbits, and dogs) to different dosages of the active ingredient.
Tests are also done with each different formulation of the product, for example,
liquids, dusts, and granulars. Pesticide toxicities are listed in milligrams of exposure
to kilograms of animal body weight. By understanding the difference in toxicity levels
of pesticides, a user can minimize potential hazards by selecting the pesticide with the
lowest toxicity that still controls the targeted pest.
Applicators may have little or no control over the availability of low-toxicity prod-
ucts or the toxicity of specifically formulated products. However, exposure can be sig-
nificantly reduced or nearly eliminated by using personal protective clothing and
equipment. For example, more than 90 percent of all pesticide exposure comes from
dermal exposure, primarily to the hands and forearms. Wearing chemically resistant
gloves can reduce this exposure by at least 90 percent. Therefore, an applicator can
lower a pesticide’s hazards to an insignificant level by using the correct PPE.
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 classi-
fied as ‘‘highly toxic’’ on the basis of oral, dermal, or inhalation toxicity must have
the signal words DANGER and POISON (in large red letters) and a graphic of a
skull and crossbones prominently displayed on their package labels. PELIGRO, the
Spanish word for danger, must also appear on the labels of highly toxic chemicals.
Acute oral LD 50 values for pesticide products in this group range from a trace
amount to 50 mg/kg of body weight. An exposure to only 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 a skull and crossbones.
A DANGER label does not provide information about the chemical’s LD 50 value.
Instead, this signal word alerts users of potentially more severe skin or eye effects
caused by the product’s irritant or corrosive properties. Pesticide products considered
‘‘moderately toxic’’ must have the signal words WARNING and AVISO (the Spanish
word for notice or warning) displayed on their labels. Acute oral LD 50 values range
Pesticides in Agriculture | 45