[stoppingdown]

This guy did perform some measurements with a geiger counter - not the Mitakon, but other lenses. It might be useful just to have an idea:

 

https://mbphotox.wordpress.com/2015/07/2...my-lenses/

 

The most active lens he measured is a Fujinon. His conclusion:

 

For comparison, when you fly from New York to Germany you get a dose equivalent of 0,1 mSv. That’s 10 nights of sleeping with the Fujinon under your pillow.
 

 

 

OTOH, it seems that the radioactive element is always an inner one, so radiation is partially reduced by other glass elements. I'd be a bit worried, though, if I had one of those lenses and I broke it, thus exposing the radioactive element.