Smoke drifting into the Salt Lake Valley from fires in Yellowstone National Park, Idaho and elsewhere in Utah has not created adverse health effects, just unusually hazy days and colorful sunsets.

The smoke has filtered into the valley slowly and is very evenly distributed in the air, said Kenneth L. Alkema, director of the Utah Health Department's Division of Environmental Health.There isn't even a potential health threat from the smoke at this time and air quality in the Salt Lake Valley is still well above federal health standards, Alkema said.

The smoke contains mostly airborne ash and some traces of carbon monoxide, but the amount of carbon monoxide from the smoke compared to that generated by vehicle exhaust is negligible, he said.

Rolf Doebbeling, an environmental health scientist with the health department, said there is a considerable delay between the time samples of the forest fire smoke are collected in monitoring filters and when the quantity of airborne particulates can be determined. Field monitors are checked on a routine schedule that can be stepped up if a health concern is more likely.

"We will not pay much attention unless it comes close to violating national air quality standards," Doebbeling said.