The effects of environmental pollutants on human and environmental health are a growing concern. Little science curriculum focuses specifically on environmental health, and little data exists on the extent to which environmental health is taught on a national level. Students have the right to access information that can enable them to make informed choices. In the political arena, legislators, lobbyists, environmental groups, and other stakeholders argue from vastly different perspectives issues of environmental health, such as the causes and consequences of global warming. Scientists, for their part, use argumentation to make progress in developing and supporting coherent theories. For several decades, education researchers have argued for the need to integrate scientific argumentation into the high school science classroom. Scientific argumentation involves making claims, supporting them with evidence, providing "warrants" or reasoning for how the evidence supports the claims, anticipating counterclaims, and preparing to respond to those counterclaims. This article describes a sequence of lessons surrounding a mock legislative hearing to help students learn about environmental health and participate in argumentation. The lessons, appropriate for biology, chemistry, or environmental science classes, use Tox Town, a free online resource developed by the National Library of Medicine, as the main source of information. (Contains 3 figures.)