Thorium gas mantles

[Bruce Pickett <SHEA136@KGV2.bems.boeing.com>]

 For decades, HPs have stood up before classes and the public while holding
 onto gas lantern mantles and saying "See these? They're radioactive!" But in
 the past year or two, the mantles have no longer contained radioactive
 materials (I suspect that the mantle manufacturers got tired of being held up
 as examples by the nuclear industry, so they eliminated the use of thorium).
 Can anyone answer these questions:

 (1) Have all manufacturers of gas mantles stopped using thorium?

 (2) I've always thought that the thorium was intentionally used to increase
 the luminosity of the burning gas mantles; what has replaced the thorium and
 is it as effective in brightening the light?

 (3) In a thorium gas mantle, what percentage of the thorium burns off and
 what remains in the mantle ash?

 (4) What is considered to be an "average" activity for thorium mantles and how
 much variability is there?

 Thanks,
 Bruce Pickett