I saw an interesting presentation by Dr. Daniel Steck at a recent conference in NewZealand. He presented information for year long outdoor measurements for MN and IA. The average levels he found were about .8 pCi/L with large areas averaging 1.5 pCi/L year round. If I recall correctly, he sampled for 1 year at over 120 outdoor sites. Sam Kirk SSEKirk@aol.com