What is the toxin and what is it primarily used for?

There are many different ways toxins are introduced into the environment. Using the textbook or another authoritative source chose a toxin that people can be exposed to and answer the following questions:

1. What is the toxin and what is it primarily used for?
2. How are people exposed and what are the potential problems?
3. How can toxin exposure be prevented or what are known obstacles to prevention?