Mercury is a naturally occurring and widely used element that can cause health and ecological problems when released to the environment through human activities. Though a national and even international issue, the health and environmental impacts of mercury are best understood when studied at the local level. "Mercury: An Educator's Toolkit" contains a variety of activities, educational videos, and other information designed to enhance students' understanding and appreciation of mercury and its potential health hazards. Depending on the needs of their curriculum, educators can select material from the most appropriate sections of the toolkit. This document, "Background Information for Educators" will assist teachers in considering the types of mercury information that best meet the needs of their students.