Smoke from the King fire has pushed air pollution into the rarely seen “hazardous” category in many areas of the Sierra Nevada west of Lake Tahoe, and is likely to remain so through the weekend.
Officials are warning residents and visitors to avoid prolonged outdoor activity in areas affected by the worst smoke, which on Friday included foothill and mountain areas of Placer and El Dorado counties and parts of Nevada and Amador counties.
The pollution consists of tiny particulate matter in smoke – known as PM2.5 because they are 2.5 microns in size or smaller. Such particles are small enough to penetrate deep into the smallest airways in the lungs and even pass directly into the bloodstream. Heavy and prolonged exposure, in addition to causing breathing problems, can contribute to heart disease and heart attacks.
“It’s going to affect your respiratory and cardiovascular systems in a negative way when you’re breathing those wood tars and soot and ash into your lungs,” said Dave Johnston, air pollution control officer in El Dorado County, which sits at the fire’s epicenter.
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“Folks should stay indoors and refrain from vigorous exercise – so, kind of hunker down. They should keep pets indoors and wait until it blows over or goes someplace else if they want to recreate.”
Skies in the Sacramento metro area have been darkened by the haze, but the smoke has hovered mostly at higher elevations and has not affected ground-level air quality in the Valley, said Lori Kobza, a spokeswoman for the Sacramento Air Quality Management District. Particulate pollution remained in the “good” range through the day Friday and is expected to remain there through the weekend, she said.
In the Sierra, conditions are much worse. Air-quality officials have situated a number of emergency mobile air-quality monitors throughout the fire zone to monitor conditions. Friday afternoon, they indicated a vast blob of “hazardous” particulate pollution stretching from Foresthill in the north to Jackson in the south. A much larger blob, considered “unhealthy” for all adults and children, stretched south from Nevada City to Angels Camp, affecting foothill and mountain elevations in five counties.
“The smoke impacts residents, the elderly, anybody with compromised immunity,” said Mike McMillan, a California Department of Forestry and Fire Protection spokesman, at Ice House near the core of the fire-affected area along Highway 50. “Firefighters just seem to endure it and accept it.”
Skies over El Dorado County on Friday were heavy with the smell of smoldering timber. Dense smoke from the King fire nearly obscured Camino, Pollock Pines and other towns from view.
At Sly Park, roadside message boards cautioned drivers: “Dense smoke next 40 miles.”
Wind conditions Thursday night and Friday pushed a lot of the smoke to the south. That is expected to change: A weak low-pressure system is sweeping across the middle of the state and is likely to blow the smoke north along the Sierra front as far as Chico and Red Bluff, according to the National Weather Service.
“We think the smoke will kind of spread to the north and west again,” said National Weather Service meteorologist Jim Mathews, based in Sacramento. “It will probably be elevated, though. I think it will be a negligible impact for the Valley.”
Much depends, of course, on how the King fire behaves. Although temperatures have cooled, the shift in wind patterns this weekend could move the fire into fresh areas of dry fuel. The fire was only 10 percent contained as of Friday night.
Another condition will affect smoke patterns: At night, changes in temperature tend to cause downslope winds, which move smoke into lower elevations. This could cause conditions to worsen in foothill communities at night and may even push smoke into outlying Sacramento suburbs such as Lincoln and El Dorado Hills.
“We are expecting the arrival of heavier smoke at ground level possibly tonight and into Saturday morning,” Kobza said. “That pattern is expected to continue through the weekend.”
Bad air quality caused by particulates is not unusual in Sierra communities and some areas of the Sacramento Valley. But that usually happens only in winter, when many people heat their homes with wood, and it almost never reaches “hazardous” levels.
“It is very unusual to see those numbers in the hazardous range,” said Ann Hobbs, Placer County air-quality specialist. “But it is not as unusual when you have a very large wildfire and the smoke has to go somewhere. The best thing to do is to take care of your own health and consider not being in the outdoors doing physical activities.”
People should be especially protective of children, whose lungs are particularly vulnerable, and adults with respiratory or cardiovascular problems.
“We’re all hoping for a quick resolution,” Kobza said. “But that fire is a monster, and the firefighters have their work cut out for them.”