With reports this week of elevated radon levels in 26 Montgomery County schools, parents and staff are urging swift action and more accountability about a problem that school district officials say they should have handled sooner.

Montgomery officials say that affected schools are being retested for radon and that they will mitigate the issue where needed. They say they think there is no immediate safety hazard, although they acknowledge that retesting should have happened when they first discovered elevated levels of the colorless, odorless, radioactive gas.

“Clearly, someone made a mistake,” Montgomery schools spokesman Brian Edwards said.

School officials could not provide information Wednesday about exactly when the 26 schools were tested for radon, but results for one — Fallsmead Elementary School — were dated 2012, according to a district document.

Parents and staff at Fallsmead, attending a Tuesday night meeting with district officials, pressed to learn why the issue fell through the cracks and how it would be resolved.

Mindy Freedman, a mother of two, challenged the district’s descriptions of radon being found at levels “slightly” higher than the Environmental Protection Agency recommends.

“I don’t know if any parents would find any increased level of risk to the health of their child acceptable, especially when MCPS had the knowledge and the power to lower these radon levels and did absolutely nothing for over three years,” she said.

Radon levels at Fallsmead were as high as 5.3 picocuries per liter of air — higher than the EPA recommended limit of 4 pCi/L, according to district data. In all, radon was found at or above the limit in 16 of 42 rooms in the Rockville school. A picocurie is a unit of radioactivity.

Several educators spoke out with concern, including Christina Brown, a teacher who noted that she worked at the school during a recent pregnancy and said that several other staff members have been pregnant while working there; some of their classrooms were among those with the highest radon levels, she said, “which is totally unacceptable.”

Rebecca Kotok, a school counselor at Fallsmead, said that when students make mistakes, teachers ask them to look at how and why they erred. Kotok asked whether the school system would strive for the same standard and launch an inquiry to figure out what went wrong.

A letter to Montgomery parents noted that the EPA recommends that areas with radon levels above 4 pCi/L be retested before taking any mitigation efforts. Results at about 10 pCi/L “demand a quicker mitigation response,” it said, and it suggests a relocation of classrooms with levels near 100 pCi/L, until radon levels are reduced.

Edwards, the district spokesman, said the results did not come close to approaching the level at which classrooms would have to be vacated.

Michelle Moyer, radon program manager for the EPA’s Mid-Atlantic region, said the agency recommends retesting at levels at or near 4 pCi/L. She said research on radon in homes suggests that there is an increased risk of lung cancer for radon levels above that level, depending on duration and amount of exposure.

Jim Keilson, president of Maryland Home Inspection Services, said he has tested homes and commercial buildings for radon for more than a decade, and he considers radon levels above 4 pCi/L troubling. “The safe zone is under 4,” he said. “It was set by the EPA.”

Jeff Leavey, radiation protection manager for Pennsylvania State University, said he would not be concerned about levels from 4 to 12 pCi/L — the range of Montgomery’s results — given the limited time students spend in the classroom and the likelihood that the results were single measurements and not indicative of long-term averages.

At current levels, “I would not be concerned about health effects,” he said.

Springbrook High School showed among the highest readings of the 26 schools, with a radon level as high as 9.8 pCi/L. Eight of 168 rooms at the high school showed elevated levels.

“The fact that the information wasn’t made public is deeply troubling,” said Jamahl Johnson, a parent at Springbrook.

The other affected schools — mostly elementary schools — are located in areas including Silver Spring, Bethesda, Potomac, Rockville and Damascus.

Chris Lloyd, president of the county teachers union, said district educators are asking about how the issue went unaddressed for so long and exactly which rooms tested high in the schools.

“I think there is concern about the potential health impacts, both for yourself as a teacher and for the kids that you’re teaching,” he said.

The issue came to light after Louis Wilen, a member of the Parents’ Coalition of Montgomery County, a watchdog group, made a public information request for school radon-test reports. Wilen said recent county action requiring home sellers to do radon tests spurred his interest.

Wilen was surprised to see that a third of the rooms at the middle school his three children once attended — Redland — showed elevated levels of radon.

“I was even more surprised to find out that MCPS had not taken any action to retest or reduce radon levels,” he said.