Elemental Bio-imaging of Thorium, Uranium, and Plutonium in Tissues from Occupationally Exposed Former Nuclear Workers

Abstract

Internal exposure from naturally occurring radionuclides (including the inhaled long-lived actinides (232)Th and (238)U) is a component of the ubiquitous background radiation dose (National Council on Radiation Protection and Measurements. Ionizing radiation exposure of the population of the United States; NCRP Report No. 160; NCRP: Bethesda, MD, 2009). It is of interest to compare the concentration distribution of these natural alpha-emitters in the lungs and respiratory lymph nodes with those resulting from occupational exposure, including exposure to anthropogenic plutonium and depleted and enriched uranium. This study examines the application of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS) to quantifying and visualizing the mass distribution of uranium and thorium isotopes from both occupational and natural background exposure in human respiratory tissues and, for the first time, extends this application to the direct imaging of plutonium isotopes. Sections of lymphatic and lung tissues taken from deceased former nuclear workers with a known history of occupational exposure to specific actinide elements (uranium, plutonium, or americium) were analyzed by LA-ICPMS. Using a previously developed LA-ICPMS protocol for elemental bio-imaging of trace elements in human tissue and a new software tool, we generated images of thorium ((232)Th), uranium ((235)U and (238)U), and plutonium ((239)Pu and (240)Pu) mass distributions in sections of tissue. We used a laboratory-produced matrix-matched standard to quantify the (232)Th, (235)U, and (238)U concentrations. The plutonium isotopes (239)Pu and (240)Pu were detected by LA-ICPMS in 65 mum diameter localized regions of both a paratracheal lymph node and a sample of lung tissue from a person who was occupationally exposed to refractory plutonium (plutonium dioxide). The average (overall) (239)Pu concentration in the lymph node was 39.2 ng/g, measured by high purity germanium (HPGe) gamma-spectrometry (Lynch, T. P.; Tolmachev, S. Y.; James, A. C. Radiat. Prot. Dosim. 2009, 134, 94-101). Localized mass concentrations of thorium ((232)Th) and uranium ((238)U) in lymph node tissue from a person not occupationally exposed to these elements (chronic natural background inhalation exposure) ranged up to 400 and 375 ng/g, respectively. In lung samples of occupationally nonexposed to thorium and uranium workers, (232)Th and (238)U concentrations ranged up to 200 and 170 ng/g, respectively. In a person occupationally exposed to air-oxidized uranium metal (Adley, F. E.; Gill, W. E.; Scott, R. H. Study of atmospheric contaminiation in the melt plant buiding. HW-23352(Rev.); United States Atomic Energy Commission: Oakridge, TN, 1952, p 1-97), the maximum (235)U and (238)U isotopic mass concentrations in a lymph node, measured at higher resolution (with a 30 mum laser spot diameter), were 70 and 8500 ng/g, respectively. The ratio of these simultaneously measured mass concentrations signifies natural uranium. The current technique was not sufficiently sensitive...

Determination of impurities in thoria (ThO2) using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS)

“…It will be interesting to analyse similar thoria samples using fsand ps-lasers by those laboratories having access to these systems and obtain a comparison of the results of ns-versus ps-and fs-lasers in view of the studies reported for determination of thorium at trace to ultra-trace levels by LA-ICP-MS [13][14][15][16].…”

Elemental bio-imaging of trace elements in teeth using laser ablation-inductively coupled plasma-mass spectrometry

“…20 Our laboratory has applied this technique to the imaging of trace elements in mouse brains, 21 osteoarthritic joints 22 and human lymphatic tissues. 23,24 LA-ICP-MS is a relatively simple technique that does not require a high vacuum ion source or suffer from severe matrix effects. Complicated and often hazardous digestion procedures are not required as it is a solid-state analyzer.…”

Multielemental bioimaging of tissues in children's environmental health research

“…LA-ICP-MS was used to study uranium (U), plutonium (Pu) and thorium (Th) exposure in lymphatic tissue from ex-nuclear workers years after suffering acute occupational exposures [20], and background levels of Th and U in human hippocampus tissue was proposed as a possible internal standard for measuring endogenous metals in tissue [21], though this approach fails to meet contemporary guidelines for internal standardization for LA-ICP-MS due to each element's extremely low abundance [17,22]. …”