On Jan 31, 12:20*am, Martin Brown
wrote:
On 31/01/2013 00:22, RichA wrote:

The Kodak Ektamate and Ektar lenses all use thorium glass. *Pretty
harmless just sitting around but I wouldn't want to press my eye to
one for any length of time.

http://www.surplusshed.com/pages/item/l3759.html

The half life of natural Thorium 232 is 3x the age of the Earth and
something similar for Lanthanum 138 rare earth glasses. The only worry
with the latter is that uranium was often present as an impurity.

--
Regards,
Martin Brown

A banana offers a thousand times as much radiation as any thorium
glass.