Measuring hot particles from air filters

Tokyo air filter #5 NaI spectrum

[This is a guest written article, views expressed are the authors alone and may not be endorsed by Safecast]

In the last month we have received 22 vehicle air filters from safecasters.  These came from vehicles used primarily in Fukushima City, Tokyo, and Iwaki.  The Fukushima City filters had total radiation levels that averaged about 2.0 uSv/hour, while the Tokyo filters averaged 0.2 uSv/hour.  The filters are analyzed by gamma spectrometry. We found cesium-134, cesium-137, cobalt-60, and uranium and its decay products in the dusts trapped on these filters.  These dusts contain enough breathable radioactive particles that people need to use care in removing and handling used car filters from Northeastern Japan.  Our group is also looking to test school yard soils for hot particles, and edible seaweed for cesium and radioiodine uptake.  People interested in doing sampling should read the sampling guide.