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. At Dartmouth we have formed a diverse group of scientists to study and teach about toxic metals in the environment. While our current focus is on arsenic and mercury, we have studied these metals in the past, and some of our colleagues at other Superfund Research Programs around the country are researching their impacts on the environment and human health.