The main efforts of the past year have been directed towards investigation of the behavior of the radioactive aerosols in actual in mining operations. Activities can be categorized as follows: Preparation of equipment for taking data in uranium mines; development of background of personnel to carry out intended experiments; research data from United Nuclear Homestake Partners Section 25 mine in the Ambrosia Lake area near Grants, New Mexico; updating of computer programs for data analysis in order to extract more information; and the development of a thermal precipitator for partical size analysis in the submicron range.