Report on the successful webinar plenary of the 4^th International Radiation Science Collaboration Center Seminar organized by the Institute of Radiation Emergency Medicine, Hirosaki University. The lecture topic was “Understanding Factors controlling radon exposure in buildings” which was presented by Dr. Wolfgang Ringer from the Austrian Agency for Health and Food Safety scheduled on 30 May 2022 at 18:00 JST. There are students, early carriers, and researchers of about 82 attendees from 21 countries, especially from Asia and Africa joined the webinar. Moreover, the on-demand video streaming lecture by Dr. Wolfgang Ringer will come soon!!!