In Germany, in 1814, Wilhelm Sattler created an extremely toxic arsenic and verdigris compound pigment, Schweinfurt green-known also as Paris, Vienna, or emerald green-which became an instant favorite amongst designers and manufacturers the world over, thanks to its versatility in creating enduring yellows, vivid greens, and brilliant blues. Most insidiously, the arsenic-laced pigment made its way into intricately patterned, brightly colored wallpapers...