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RE: Thorium Lenses



NCRP Report No. 95 addresses the issue of thorium used in various 
optical glass items, primarily to improve the refractive index.  The 
glass can be as much as 30% thorium by weight.  Surface dose rates from 
some of these lenses can be quite high. (alpha)

NRC regulations on the licensing, possession, and use of thoriated glass 
can be found in 10CFR 40.13c(7).  

Ed Tupin
RSO, Center for Devices and Radiological Health
EAT@fdadr.cdrh.fda.gov
(301) 827-1230
Fax:  (301) 594-4760