Hi Keith, I highly recommend NCRP 94, 1987 and UNSCEAR 93. > Can someone direct me to a good reference for concentrations of cosmogenic > and other naturally occuring isotopes in the environment. > > Many thanks in advance. > > Keith Welch > Thomas Jefferson National Accelerator Facility > Newport News VA > welch@cebaf.gov Regards, Jim Muckerheide jmuckerheide@delphi.com