As Canada wildfires rage, experts examine the ramifications

Since early May, wildfires have been raging in and around the city of Fort McMurray in Canada's Alberta province, the country's oil-sands capital. The latest evacuation took place on Monday: Some 8,000 workers at oil-sands facilities and camps north of the city were ordered to leave when a new fire to the west began heading north. The air quality health index had soared by then, reaching 38; the scale normally goes from 1 to 10. More than two weeks earlier, 88,000 residents had been ordered to l