Radiation released into the air in southern Utah during several recent wildfires came from naturally occurring material and not from the fires, according to a University of Nevada, Las Vegas study.
From July 5 to July 10, federal radiation monitors of the Community Environmental Monitoring Program recorded spikes in gamma radiation at Milford, with readings at times far above normal.
Usually, this form of radiation is measured at 20 or 21 microrems per hour. But during that period the readings reached as much as 136.8 microrems per hour.
However, that's still not high enough to cause health effects.
Some residents had feared the increase in radiation in the air had been caused by wildfires.
Downwinder groups cited the heavy radiation that fell on the region during open-air nuclear testing at the nearby Nevada Test Site in the 1950s and early '60s.
But the UNLV report released on July 20 seemed to rule out fallout and an official from the National Nuclear Security Administration agrees with the report.
The study was conducted by the UNLV health physics department,
Radiation Services Laboratory.
After analyzing air samples collected in Milford, the scientists concluded fallout was not involved.
"Initial screening by gamma spectroscopy did not indicate the presence of unusual levels of man-made radionuclides in these filters," the report said.
Cesium-137, which is a long-lived component of fallout, "was not detectable in any of the filter samples analyzed."
However, several naturally occurring radioactive substances were
identified in the samples: Beryllium-7, produced in the upper atmosphere; Lead-212 and Lead-214 derived from the decay of natural
uranium and thorium, and Potassium-40, "which is present in
atmospheric dust particles and virtually all other types of geological materials."
Also tentatively identified were Uranium-235 and Radium-226, natural materials that were found in only small amounts.
"Other natural (radioactive) components are present only in variable and relatively small amounts, and no man-made radionuclides were detected," the report concludes.
"It's all natural. They did not detect any radiation that could be associated with worldwide fallout," said Darwin Morgan, a spokesman for the NNSA in Las Vegas.