UC IPM Online UC ANR home page UC IPM home page

UC IPM Home

SKIP navigation

 

Pesticides and Water Quality

General Toxicology

Toxicology

  • Toxicology is the science that deals with poisons and their effect on living organisms.

Toxicity

  • Toxicity is the inherent ability of a pesticide to cause harm to a specific organism.
  • Some pesticides are more toxic than others and present higher risks to users, nontarget organisms, and the environment.
  • The effect of the pesticide (the toxic reaction) is related to the amount of pesticide (the dose) applied.
  • Toxicity is often measured in LD-50, the Lethal Dose to kill 50% of exposed individuals, or LC-50, the Lethal Concentration in water or air to kill 50% of exposed individuals of a species.
  • LD-50 does not provide information about long-term (or chronic) effects such as cancer, sterility, and permanent nerve damage that can result from repeated low level exposures.
  • The Extension Toxicology Network provides more information on toxicity of specific pesticides.

Half-life

  • The half-life is the length of time it takes for a pesticide to lose half of its toxicity in a given environment.
  • Pesticides that break down rapidly are less likely to cause harm.

Indicator organisms

  • An indicator organism is a test species that is used in experiments to measure the toxicity of poisonous materials.
  • Indicator organisms are exposed to various levels of toxic materials over a period of time in order to determine their potential toxicity to the organism and to evaluate their effects on survival and reproduction.
  • Ceriodaphnia and Hyalella are tiny aquatic invertebrates used as indicator organisms to measure toxicity in water.

Drop of diazinon in volume of 2 pools is toxic to organism
Click on image to enlarge

Illustration by Celeste Rusconi


Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2007 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

Accessibility   /WATER/U/toxicology.html revised: November 8, 2007. Contact webmaster.