Pesticides are natural or human-made substances used to kill pest species such as rodents and insects. It is not surprising that many of these substances are highly toxic not only to the pests, but to other biological organisms as well. Pesticides are used in forests, agricultural regions, parks, residential areas, and within the home.

The bulk of pesticide use is related to agricultural pest control. In fact, pesticide application increased dramatically when intensive agricultural methods began to be used near the start of the twentieth century. Although pesticides clearly help to increase agricultural production, they also harm humans and other animal species. In addition, they contaminate the environment, often persisting in water, air, and soil for long periods of time. The World Health Organization reports over one million human pesticide poisonings every year, including twenty thousand that result in death.

These numbers do not include the slower and...