Dear Radsafers: I would liek to know what is the 'official' US background radiation level and the reference for it. How does this value compare with other countries? is it a publication on this. Thanks Kwan Kwan Hoong Ng, PhD, MIPSM Department of Medical Physics University of Wisconsin 1300 University Avenue Madison, WI 53706 Office 608 263 4355 Home 608 231 9050 Fax: 608 262 2413