Smoke from wildfires in British Columbia, including this one at Pelican Lake in the B.C. Interior, are sending clouds of smoke over western Alberta. ((CP))

Smoke from wildfires in British Columbia continued to hang over Edmonton on Friday, sparking fresh warnings from health officials.

People who already have respiratory conditions are most at risk, doctors say, but the smoke can also be harmful to otherwise healthy people if they exert themselves, and that's bad news for the 4,000 entrants registered to compete in the Edmonton Derby marathon and half-marathon scheduled for Sunday.

The race is still on but Dr. Andre Corriveau, Alberta's chief medical officer of health, said Friday he's been in touch with the organizers and is advising athletes to use caution and common sense when competing.

"People will have to adjust their expectations perhaps, or maybe some people may choose to do the half-marathon instead of the full one," he said. "So it's really about providing guidance and letting people make their own decisions about what pace they want to run and how much of it they want to do."

Organizers had hoped for a record-setting time because the course is relatively flat and the temperature is expected to be a comfortable 16 C. However, the poor air quality could affect finishing times.

Race organizer John Stanton said conditions are being monitored but, so far, he's only heard from one athlete concerned about the smoke.

"People who are running in the half and full marathons are probably in their peak physical conditions," he told CBC News. "And with the weather the way it's clearing and a chance of rain today and tomorrow, we should have perfect running conditions for the half-marathon and full-marathon. "

Athletes concerned about their health will be allowed to race a shorter distance, Stanton said.

Even golfers are feeling the effects of the smoky conditions.

Brad Lowrie braved the smoke to play a round of golf at the Victoria Golf Course, but after firing a tee shot at the seventh hole he couldn't be certain where his ball landed.

"Well, we're not sure if it went in the bunker or maybe to the opposite side of the green," he said. "We won't really know until we get there. Because of the haze we can't really tell where the ball went."

Katlin Greening had hoped to get in another round of training for a half-marathon on the weekend but she gave up after only two kilometres.

"It's actually hard to breathe," she said. "I'm going home right now. I'm just going to go to the gym today."

The smoke is no laughing matter for volunteers such as Brooke Butler at this year's Fringe Festival. 

"I'm noticing a lot of wheezing, a lot of, generally, just difficulty in breathing," Butler said, her mouth and nose covered by a white surgical-style mask.

There is no end in sight to the smoky conditions.


With files from the CBC's Paul Moore