At noon, the sky is so dark with smoke that cars drive down Qayarah’s main road with their headlights on. People walk with their heads down, masks or scraps of cloth clamped over their mouths to filter the sulfur fumes. The town is free from the Islamic State (IS) militant group, but it can barely breathe.A choking fog of oil soot and sulfur is only one aspect of the damaging legacy IS has left after its two-year occupation of Qayarah, 60 kilometers south of Mosul. Residents also suffered …