This essay examines the widespread mercury poisoning that afflicted Iraq in 1972 as an entry point into a broader discussion of boundaries and nations in global environmental history. After poor harvests, the Iraqi government invested heavily in Green Revolution “wonder wheat,” which they had coated in mercury-based fungicides to protect it in transit from Mexico to Iraq. After a series of unfortunate events, the wheat arrived late and peasants began feeding the tainted seed to their livestock and to their families, instigating a massive mercury epidemic. Rather than following the national story, however, this essay examines its causes in the global context, pointing to trade, agriculture, climate, and other environmental factors as features warranting investigation. This kind of approach—putting mercury at the middle of the narrative—offers historians the opportunity to revisit questions of national, transnational, postnational, and bioregional histories with new questions and perspectives.