The first air samples collected by state authorities show that radiation wafting from Japan is at barely detectible levels and poses no threat to public safety in North Carolina.
Officials at the Radiation Protection Section expected infinitesimal increases in background radiation after Progress Energy and Duke Energy reported slight increases last week during routine monitoring at their nuclear plants in the Carolinas and in Florida.
State officials said today that initial air sampling confirms their expectations. The Radiation Protection Section, within the N.C. Department of Environmental and Natural Resources, analyzed four air samples taken Sunday and Tuesday.
The radioactive fallout is the result of malfunctioning Japanese reactors that were damaged by a tsunami earlier this month. The Japanese plants have lost emergency cooling equipment, resulting in melted nuclear fuel and radioactive releases from several reactors and spent fuel pools.
As a precaution, N.C. officials have stepped up monitoring to daily samples of air, water and milk. Previously such sampling took place on a monthly and quarterly basis.
The first radioactive isotopes detected have been iodine-131, which loses half its radioactivity every eight days and decays to a stable (non-radioactive) state in about 80 days.
Officials also expect other isotopes to arrive from Japan, including cesium-137, which has a half-life of about 30 years and takes about three centuries to decay to a stable state.
N.C. officials detected trace amounts of these and other radioactive isotopes in 1986 in the wake of the Chernobyl nuclear accident in the former Soviet Union. At the time, there were no risks to public safety, officials said.
"A lot depends on the contamination that drifts down here from Japan," said Gerald Speight, an environmental program consultant with the Radiation Protection Section. "These amounts are barely above the detection capability of the modern radiation detection instruments."