THE GIANT WILDFIRE  burning at the edge of Yosemite National Park has not only destroyed buildings and threatened water supplies, electricity and sequoias, it has also unleashed a smoky haze that has worsened air quality more than 100 miles away in Nevada.

The plume from the Rim Fire in California triggered emergency warnings in the Reno and Carson City area.

Schoolchildren were kept inside for the second time in a week, people went to hospitals complaining of eye and throat irritation and officials urged people to avoid all physical activity outdoors.

Firefighter Brandon Wenger stands along Highway 120 while monitoring a backburn during the Rim Fire. Pic: AP Photo/Jae C Hong

The Rim Fire, so far, has burned through 293 square miles, destroyed more than 100 structures, including 85 tent cabins at a camp run by the city of Berkeley, and threatened water supplies, hydroelectric power and giant sequoias.

This morning, authorities said the blaze was 23 percent contained, with crews aided by higher humidity continuing to make progress against it overnight.

Smoke

In Nevada, evidence of the Rim Fire is in the smoke-filled sky. The air quality index briefly surpassed the rare “hazardous” level east of Lake Tahoe before improving slightly.

It hovered around the next-most serious stage of “very unhealthy” for all populations in the Reno-Sparks area 30 miles north.

Dennis Fry, a Reno auto body specialist for nearly 30 years, remembered smoke this thick when he worked on a logging crew and helped fight fires in Oregon during the 1970s.

A Merced Grove cabin, next to the giant sequoias, is covered in metal foil by CalFire crews trying to protect structures from the Rim Fire burning through trees. Pic: AP Photo/National Park Service

Everyone should avoid all physical activity outdoors when the air quality index reaches “hazardous,” considered “emergency conditions,” the Nevada Division of Environmental Protection said on its website.

“People with heart or lung disease, older adults and children should remain indoors and keep activity levels low.

Renown Regional Medical Center in Reno has experienced a “slight increase” in emergency room visits as a result of the smoke, said Jennifer Allen, the hospital’s clinical nursing supervisor.

“Patients are experiencing shortness of breath, eye and throat irritation, cough and headache due to the heavy smoke and poor air quality,” she said, adding that people with asthma and other respiratory ailments were most affected.

The pollution levels are among the worst ever recorded for small particulates around Carson City in the state’s air monitoring records dating to 2000, according to JoAnn Kittrell, public information manager for Nevada Division of Environmental Protection.

“It’s very unusual,” she said. “We just happen to be in the direct path of the plume from Yosemite.”

Two firefighters monitor a back burn during the Rim Fire. Pic: AP Photo/Jae C Hong

The previous peak reading in Reno came on Friday when the air quality index closed in on the “very unhealthy” stage. Schoolchildren were kept indoors during break, high school football practices and scrimmages were canceled through the weekend and an annual air show at Lake Tahoe was canceled due to low visibility.

Carol Chaplin, executive director Lake Tahoe Visitors Authority, said some hotels and motels reported cancellations earlier in the week, but so far there hasn’t been any major impact for the upcoming Labor Day weekend.

The fire caused air pollution problems in California cities far away from the fire, including those in the Sacramento region.

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