The rich and nuanced stories in this volume deepen our understanding of the multiple ways in which toxic environments have been created and continue to be sustained. You may feel, as we do, overwhelmed by all that remains debated, unknown, and uncertain. However, simply acknowledging that uncertainty seems to be an important first step in confronting our toxic present. As so many of our cases have shown, the creation and regulation of contaminated places has historically favored economic growth and military-industrial interests. Uncertainties around toxicity have either been ignored or used to justify action rather than caution. But in recognizing