Public health officials are warning Tuolumne and Calaveras county residents to be cautious about exercising and outdoor activities as smoke billows in from the Rim Fire.
Smoke reduced visibility in areas around Groveland to less than a mile Monday, meaning it was thick enough to pose problems for the entire population there, said Tuolumne County Public Health Officer Dr. Todd Stolp.
"That's very poor air quality for everyone, not just those with risks," Stolp said Tuesday.
The Tuolumne County Air Pollution Control District issued an air quality alert Tuesday for Tuolumne County, including portions of Yosemite National Park. The alert is in effect until noon Friday, Aug. 23.
Meanwhile, the Calaveras County Air Pollution Control District advised Calaveras County residents that "unhealthy" levels of smoke can be expected at both upper and lower elevations in the county.
Concern about smoke and the behavior of the fire prompted Big Oak Flat-Groveland Unified School District to postpone its first day of school, which had been scheduled for Tuesday, and cancel it again Wednesday.
"The smoke was one issue, the road closure was another, and the fact that nobody knows where the fire is going," said Big Oak Flat-Groveland Superintendent Dave Urquhart. "There's a lot of worry."
Summerville Union High School District remains in session - although coaches have been advised to restrict athletic activities.
Sonora Union High School District Superintendent Mike McCoy said Sonora High's first day of school will continue as planned.
"We're not cancelling school, but I'm asking my staff to be mindful of students and their exertions," he said. "We're not going to have anybody running the mile."
Smoke from forest fires can cause respiratory problems by creating inflammation in airways and increasing mucus production there, Stolp said. It heightens the risk of infection and can also transfer harmful chemicals and fumes from man-made structures that burn down.
People with certain preexisting health conditions are more likely to experience ill effects from smoke inhalation. Those conditions include asthma, cancer, heart or lung disease, and other chronic health problems. Young children, pregnant women and the elderly are also at greater risk.
The first effects of smoke are often coughing, an irritated throat and burning eyes. Smoke aggravates asthma symptoms and can cause shortness of breath for those with circulatory problems.
Patients with circulatory problems might also experience ankle swelling, the result of strain from their respiratory and circulatory systems working harder, Stolp said.
A Tuesday release from the Calaveras Air Pollution Control District advised those with any chronic heart or lung disease, including asthma, to "closely monitor" their health and contact their doctors immediately if they experience symptoms such as difficulty breathing.
Other symptoms to watch for include chest tightness or chest pains, palpitations, nausea, fatigue or lightheadedness.
People at risk should consider going to an emergency shelter or leaving the area until smoke conditions improve.
The Mother Lode's hilly topography, combined with varying wind direction, has caused smoke from the Rim Fire to gather in some places while bypassing others.
Stolp advised people to monitor air quality by noting whether they can see nearby landmarks. Visibility of five miles means sensitive populations and people with preexisting health conditions should stay inside.
At three miles or less, even healthy people should avoid outdoor activities like jogging. Patients with asthma should use a peak flow meter to monitor their condition and closely follow their treatment plans.
Mother Lode residents are advised to shut their windows and use air conditioning to keep cool. The evacuation center at the Mother Lode Fairgrounds in Sonora is available to those who lack air conditioners or need cleaner air.
Air pollution control districts recommended against running any fans that bring smoky air inside, including swamp coolers. Wall or window-unit air conditioners should be set to "re-circulate," with fresh air intakes closed.
HEPA filters, or "high-efficiency particulate air" filters, can screen smoke particles, Stolp said.
Information on smoke can be found on Tuolumne County's website at http://www.tuolumnecounty.ca.gov/ by selecting "Air Pollution Control" from the drop-down menu on the left.
The page includes links to air quality information from temporary air quality monitors in Groveland and Columbia.
For more information on air quality, call the Tuolumne County Air Pollution Control District at 533-5693 or the Calaveras County Air Pollution Control District at 754-6601.