About RadNet Laboratory Analyses
Detailed laboratory analysis of air filters detects trace amounts of radioactive material that the sensitive near-real-time air monitors don't pick up. It identifies the radioactive material and their average concentration in picocuries per cubic meter (pCi/m3) over the sampling period.
Generally, RadNet uses stationary monitors to collect data. However, EPA can also set up additional, portable (deployable) monitors to increase coverage during radiological incidents.
There are two ways of collecting samples to test for airborne radionuclides:
- Filter Sampling: RadNet stationary and deployable monitors pass air through a filter which traps particulates. The filter is sent to National Analytical Radiation Environmental Laboratory (NAREL) for a sensitive laboratory analysis that identifies the radionuclides on the particles.
- Air Cartridge Sampling: RadNet deployable monitors also pass air through a cartridge that contains charcoal. The cartridges collect radioactive particles and gases in much the same way that a home charcoal air filter traps cooking odors. The cartridges are sent to NAREL for a sensitive laboratory analysis that can detect gaseous radioactive material in the sample.
Twice weekly, monitor operators collect filters and send them to NAREL for analysis. A gross (total) beta analysis is performed on each air filter, followed by a gamma scan if the beta activity is greater than 1 pCi/m3. Each year, a composite sample of the air filters for each monitors is analyzed for plutonium (Pu-238, Pu-239, Pu-240) and uranium (U-234, U-235, and U-238).
EPA routinely samples cow's milk at more than 30 stations every three months. Milk is consumed by a large portion of the population, especially children. Milk sampling is a good indicator of children's exposure to radionuclides, and is a good general indicator of radionuclides present in the environment.
Scientist use gamma spectrometry to analyze milk samples for fission products such as iodine-131 (I-131), barium-140 (Ba-140), and cesium-137 (Cs-137). These radionuclides are the ones that could be present after a nuclear accident. Less often, scientists also analyze samples for strontium 90 (Sr-90). All results are measured in picocuries per liter (pCi/L).
EPA's RadNet Drinking Water Program obtains quarterly drinking water samples from more than 50 sites across the country and sends them to our laboratory for analysis. All results are measured in picocuries per liter (pCi/L). Every sample is analyzed for tritium (H-3) quarterly. One sample from each station is analyzed for iodine-131 (I-131) once a year. An annual composite sample from each monitoring station is analyzed for gross alpha and beta radiation. Any sample with elevated gross alpha radiation will be analyzed for radium-226 (Ra-226), plutonium (Pu-238, Pu-239, and Pu-240), and uranium (U-234, u-235, and U-238). If the radium-226 result is between 3 and 5 pCi/L, then the sample is analyzed for radium-228 (Ra-228). All of the annual composite samples are also analyzed for gamma-emitting radionuclides. Twenty-five percent (25%) of the annual composite samples from each monitoring station are analyzed for strontium-90 (Sr-90).