Re: Contaminated Lead Products Update

["Tupin, Edward A. 301-827-1230 Fax 594-4760" <EAT@CDRH.FDA.GOV>]

Some follow-up on the lead contamination issue.  

Eons of geologic time allowed sufficient decay of uranium into radium 
into radon and on to lead-210 to reach the levels seen (as previously 
noted, 4 nCi/g of lead) in the ore body.  Because of the metallic nature 
of the material and the size of the ore body, escape of radon from the 
ore body would be minimal, thus it would decay to lead-210 effectively 
in situ.  The area of the world (Brazil) from which the lead came is 
known to be rich in uranium.  (Some of the highest known natural 
background radiation is found there.)  Mining and at least two 
subsequent smelting operations effectively separated the uranium/radium 
(and off-gassed the radon) from the lead, with the lead-210 following 
the lead 204, 206, 207 and 208 (all stable) chemically in the smelting 
process.  Lead can be produced commercially at 99.999+% pure.  Note also 
that lead melts at a much lower temperature than uranium.  

The composition of the imported material (65% tin/34.5% lead/0.5% 
bismuth) is not a naturally found mix, which probably means that an 
additional smelting step was involved to produce it.  (The smelting/ 
mixing has not been confirmed.)  This additional smelting would again 
remove non-lead elements (such as Rn, Ra and U). 

[The preceeding is a far different situation from waiting a reasonable 
fraction of a human lifetime for lead-210 to ingrow from a separated 
radium-226 material.]

In answer to the "contamination" question: 

The following definition of radioactive contamination is taken from the 
Radiological Health Handbook,U.S. Department of Health, Education and 
Welfare, Public Health Service, Food and Drug Administration, Bureau of 
Radiological Health, and appeared in the 1955, 1960 and 1970 editions of 
the document.

"CONTAMINATION, RADIOACTIVE:  Deposition of radioactive material in any 
place where it is not desired, and particualy in any place where its 
presence may be harmful.  The harm may be in vitiating the validity of 
an experiment or a procedure, or in actually being a source of danger to 
personnel."

The first part of the above definition aptly describes the situation of 
lead-210 in lead-containing protective devices.

The preceeding is the personal commentary 
of the author
Ed Tupin
RSO, Center for Devices and Radiological Health
Food and Drug Administration
EAT@cdrh.fda.gov
(301) 827-1230
Fax:  (301) 594-4760