I'll cite the study :
"As described above, conservative and precautionary measurements of radon arising from a notional collection of 15 pocket watches, 18 wrist watches and a couple of miscellaneous items indicate that radon concentrations routinely exceed the UK HPA/NRPB Domestic Action Level of 200 Bq m-3 under conditions of high ventilation, rising to over 10 times that Action Level at lower ventilation rates."
"Our tests for radon demonstrate that a collection of watches with radium based paint can raise radon concentrations in a room where no radon was previously recorded. It is significant that the average concentration in this continuously actively ventilated room rose from negligible to over 200 Bq m-3, peaking at over 3000 Bq m-3 when the air circulation systems operated at reduced rates."
Seems pretty massive to me, although I don't know what they mean by high ventialtion. But I'll check a product from your link, the only way to know for sure is that I do radon measurments myself isn't it ?
(The piece is now sealed and stored in my garage)
Only sounds high. US limit is 4pCi/L. 0.037 Bq per pCi and 1000 liters per M3, I'll let you do the math.
There are radon spas still open with levels up to 5200 Bq m-3, regulators state that there is no safe level but spa operators claim medical benefit and have not been shut down. Here we enter the discussion on radiation hormesis and linear no-threshold model of dose response.