This visualisation speaks about the ways in which toxics can be present yet invisble, the uncertainties around them and the local understandings and fears related to this not-knowing, or knowing after the fact, and the material traces and infrastructures of industrial projects through which toxics continue to spread and may be made visible.
I really appreciate the historical contextualization provided in the choice of visualizations and captions here. It almost seems to write against spectacle... or at least, its general privileging in discourses on toxicity and disaster. Slow violence is certainly relevant here, although I don't feel like that fully encompasses the phenomemon you're getting at in Flint.