Kevin Schafer / Oil refinery with Mount Baker behind, seen from Fidalgo Bay, Anacortes, Washington

Kevin Schafer / Oil refinery at sunrise spewing gas effluence out of smoke stacks, Anacortes, Washington

Yva Momatiuk & John Eastcott / Smokestacks spewing smoke, Navajo generating station near Page, Arizona

Ingo Arndt / Smoke emerging from power plant stacks, Lake Powell area, Utah

Yva Momatiuk & John Eastcott / Smokestacks spewing smoke, Navajo generating station near Page, Arizona

Gerry Ellis / Air pollution from Weyerhaeuser paper pulp plant along Columbia River, Washington