I agree Radon gas is an issue. I remember that I once got an e-mail of someone working at an environmental agency in Norway. He wanted some help on an issue with determining a statistical relationship between soil / rock types and measured Radon levels in houses. Now I'm neither an expert on statistics or radioactivity, but I had developed a highly automated tool in a much used Geographical Information System (the GIS program ArcView by ESRI, the "Microsoft" of the GIS IT world) that allowed you to interpolate measurements like that. That's why he came to me.
Originally Posted by Mark Layne
Anyway, back to your remark: Although the measurements showed no immediate concerns with moderate usage of 4 hours / week, a cumulative exposure of an unprotected Ektar lens 24 hours a day, 365 days a year at close proximity, WILL cross the 1000 microSV safety zone as determined by law.
It's probably not without reason many of these old lenses show a brownish radiation damage to the lens, as described by Michael Briggs here:
So, all in all, I would keep it stored safely when not in use...