This essay offers a new approach for conceptualizing the environmental impact of chemicals production, consumption, disposal, and regulation. Environmental protection regimes tend to be highly segmented according to place, media, substance, and effect. Existing scholarship often reflects this same segmentation, by focusing on a locality, specific chemical, social movement, or regulatory body. In turn, as new environmental measures are introduced to deal with pollution and toxicity, they tend to focus on controlling future effects rather than dealing with the accumulated contamination from past industrial activity and waste. In chemical substances we encounter phenomena that are at the same time voluminous and miniscule, regulated yet unruly. Inspired by recent work on materiality and infrastructures, we focus on the concept of residues as both material and political entities. Following residues, we argue, helps us see how the past has been built into our chemical environments and regulatory systems, and why contaminants seem to always evade control.