LEAVENWORTH — The Leavenworth Oktoberfest Marathon and Half-Marathon event set for Saturday morning is full steam ahead, but with a big caveat: If air quality worsens significantly by race time, organizers are reserving the right to cancel the race.

“The air quality the last few days has been good or moderate. If it stays that way, we feel good about holding the race,” organizer Ian Crossland said Thursday. “If that were to change, we’d consult with health officials and make a decision. We are closely monitoring conditions.”

On Thursday, air quality was considered moderate in the Leavenworth area, according to the state. In contrast, air quality was considered unhealthy in the Wenatchee area.

Air quality has been a concern in the region since a lightning storm ignited several wildfires in Chelan County on Sept. 8. Since then, smoke from the fires has created more of a health problem in Wenatchee and Cashmere than in Leavenworth.

Participants can check for updates on the event’s status at www.facebook.com/leavenworthmarathon and teddriven.com/events/2012-leavenworth-oktoberfest-marathon.

“Our main priority is the safety of racers rather than putting on a race just because someone has trained,” said organizer Lynda Finegold. “We know what comes first.”

Close to 2,100 runners — the cap for the two races — are expected to gather at the starting lines Saturday morning. The marathon starts at 7 a.m. on Icicle Road near the Johnny Creek Campground. The half-marathon begins at 9 a.m. at the Leavenworth Fish Hatchery. Both races finish at the fish hatchery.

In late September, with smoke from the wildfires lingering in the region, organizers offered anyone who had registered for the event to opt out and receive a free entry in next spring’s Wenatchee Marathon and Half-Marathon instead. Crossland said more than 200 runners took advantage of the offer. But most of those spots have since been filled by those on a waiting list.

This is the first time a registration cap was imposed. The event has grown rapidly in recent years and concerns arose about traffic and parking.

“In order to put on a good race for runners, we needed to cap it,” Crossland said.

Athletes will find only minor changes to the courses this year. On Icicle Road, runners will need to run on the road’s shoulder rather than occupy a lane of traffic as they have in the past. They will continue to traverse some trails but sandy trails located near the fish hatchery have been eliminated from the course.

“People like the mixed surfaces. They just like solid mixed surfaces,” Crossland said.

Proceeds from the event go toward a University of Pennsylvania cancer biology lab as well as 10 local organizations, including some school groups. About 150 volunteers will be lining the course.