Acute Toxicity and Acute Effects
Part 2, Section 1: Pest Management
Using Pesticides Safely
Acute toxicity and acute effects
Acute toxicity of a pesticide refers to the chemical’s ability to cause injury to a person or animal from a single exposure, generally of short duration. The four routes of exposure are dermal (skin), inhalation (lungs), oral (mouth), and eyes. Acute toxicity is determined by examining the dermal toxicity, inhalation toxicity, and oral toxicity of test animals. In addition, eye and skin irritation is also examined.
Acute toxicity is usually expressed as LD50 (lethal dose 50) or LC50 (lethal concentration 50). This is the amount or concentration of toxicant required to kill 50% of a test population of animals under a standard set of conditions. LD50 values of pesticides are recorded in milligrams of pesticide per kilogram of body weight fo the test animal (mg/kg), or in parts per million (ppm). LC50 values of pesticides are recorded in milligrams of pesticide per volume of air or water (ppm). To put these units into perspective, 1 ppm is analogous to 1 inch in 16 miles or 1 minute in 2 years.
The LD50 and LC50 values found in products’ Material Safety Data Sheets (MSDS), which are available from the supplier or product manufacturer when pesticide products are purchased. Most are also available from various online sources including the manufacturer’s Web site or through various search engines as listed on our Web site at www.pested.psu.edu/resources/web/labels. For many reasons, especially in an emergency situation, maintaining a file with copies of the label and MSDS for each pesticide product used is highly recommended.
The LD50 and LC50 values are useful in comparing the toxicity of different active ingredients as well as different formulations of the same active ingredient. The lower the LD50 value of a pesticide, the less it takes to kill 50% of the test population, and, therefore, the greater the acute toxicity of the chemical. Pesticides with high LD50 values are considered the least acutely toxic to humans when used according to the directions on the product label.