PNNL

Abstract

We appreciate the opportunity to respond to the letter from Lykken and Momcilovic regarding the Capstone depleted uranium (DU) aerosol study, in which they raise the question of the potential for creation of DU nanoparticles and the risk of exposure and concomitant health effects. This issue can be addressed at two different levels: 1) whether DU nanoparticles could have been produced, and 2) whether persons within the aerosol environment could have been exposed to these nanoparticles. We cannot rule out the possibility that DU nanoparticles could have resulted from the highly energetic interaction of a large-caliber DU penetrator and DU (Abrams only) or non-DU (Abrams or Bradley) armor. However, based on visual and instrumental analysis of hundreds of microscopic samples derived from cascade impactor stages, filter samples, moving filter samples and collected bulk powders, little to no evidence was obtained that demonstrated the existence of DU nanoparticles. Given that the initial atmospheric aerosol concentrations within both the Abrams and Bradley were extremely high, tens of grams per cubic meter, coagulation and agglomeration of primary aerosol particles occurred readily and very rapidly within the crew compartment atmosphere. Deposition and clearance behavior of any nanoparticles would have been subsumed by the aggregate particles on which they resided.