Sierra Sun: It’s like they say, “What happens in Vegas, stays in Vegas.” The same is true for pollutants in the Tahoe Basin, says Thomas Cahill, the air quality expert for the Environmental Protection Agency’s Region 9 Sierra Nevada Public Land Management Association, and member of the University of California at Davis “Delta Group” that regularly audits Tahoe’s most challenging environmental issues. During the winter months, an inversion layer traps a pocket of warm air in valley areas …