Nearly three-quarters of the elements that make up the universe are metals. Though they are abundant in nature, and though many are essential for life, some metals can be toxic to living things when they build up in water, soil or food.

Worldwide, there is growing awareness of the extent and complexity of this problem. Dartmouth University's Center for Environmental Health Sciences has formed an interdisciplinary research program to study the way toxic metals affect ecosystems and human health.

Viewers can start with a metals primer that explains what the metals are; where they come from; what toxic metals are and the difference between heavy metals and toxic metals; what role metals play in living things; how can metals harm living things; and how some metals can be both good and bad for human health.

The metals listed (not all of them have active links) include:

• Arsenic
• Cadmium
• Chromium
• Copper
• Iron
• Lead
• Mercury
• Nickel
• Silver

Each one has a Q&A covering what the metal is; where it is found; how it is used; benefits and detriments to human health; symptoms of exposure; government standards and guidelines; and links to additional information.

There is also an entertaining section, with numerous graphics, called Stories and Histories. It tells the story of the metals' uses throughout history, from murder to chrome bumpers.

The Research section covers:

• Scientific Goals
• Current Research Projects
• Shared Technical Resources
• Abstracts and Technical Papers

Other sections of the Web site include News (articles written on toxic metals), Dialog (which allows viewers to ask questions about toxic metals), Resources (quite extensive), and Outreach Programs.