Depleted Uranium contamination by inhalation exposure and its detection after ~20 years: Implications for human health assessment.

Summary of Study

Parrish RR et al., Science of the Total Environment (2007) 
Excerpts of journal article.

"Inhaled depleted uranium (DU) aerosols are recognized as a distinct human health hazard and DU has been suggested to be responsible in part for illness in both military and civilian populations that may have been exposed...We show using sensitive mass spectrometric techniques that when exposure to aerosol has been unambiguous and in sufficient quantity, urinary excretion of DU can be detected more than 20 years after primary DU inhalation contamination ceased... It seems reasonable to conclude that a chronically DU-exposed population exists within the contamination ‘footprint’ of the munitions plant in Colonie, NY."

NL Industries Contamination
"This study investigated the NL Industries uranium contaminated site and a small cohort of individuals that... resided near to or worked in the plant. It was involved in processing DU and to a lesser extent enriched uranium (EU), in Colonie", NY. " The plant emitted a DU (and possibly minor EU) aerosol plume arising from combustion of metallic uranium milling waste, over a period of decades until plant closure in 1984.... During the 23 years of active uranium emissions, many tons of fine uranium, mostly in the form of combusted oxide particles settled downwind from the plant.... The data from this study and from additional 2006 soil samples (Lloyd, unpublished data 2007) were added up to determine that more than 5 tons of DU was deposited, primarily by aerosols, in the first 600 meters of radius from the plant, and that soils as far as 4 km from the plant have low level DU contamination. It is probable that between 5 and 10 tons of DU aerosols were historically emitted. This quantity is comparable to the total mass of respirable DU particles produced during the entire 1991 Persian Gulf Conflict, considering the proportion of all expended munitions likely to become aerosolized during hard target impact-related combustion."

Tests Show Depleted Uranium Internal Contamination
"This study documents residual internal DU contamination in all of the former employees tested (5 were tested) and in 10–20% of the ~20 tested individuals who either lived or worked in close proximity to the plant for at least 5 years during its active phase of emissions. The low number of individuals tested in our study precludes a quantitative extrapolation to the nearby population as a whole; this can be done only by testing a larger group. However, the detection of anomalous uranium in 100% of workers and up to 20% of our ‘residents’ cohort is in itself significant, since no previous study has documented evidence of DU exposure to aerosols more than 20 years prior...Individuals exposed to substantial quantities of DU aerosols are likely to retain a DU-positive signature for the rest of their lives."

"Five factory workers continue to excrete high amounts of uranium dominated by a DU isotopic signature... The persistence of high excretion rates of uranium in urine in workers, more than 20 years since active exposure, indicates that the body burden of uranium must still be significant, whether retained in lungs, lymphatic system, kidneys or bone..."

"Of the DU-positive residents’ cohort, four had 238U/235U values ranging from 138.9 to 151.7, though two of these four are only marginally distinguishable as containing DU. The natural value is 137.88...Although most ‘residents’ did not have detectable DU, they may have been contaminated, but to an extent that has not been detected by our measurement threshold... With a few exceptions, all tested individuals lived or worked near the plant for 10 years or more during the active period of aerosol emissions from 1958 to 1981."

Implications for Human Health Assessment
"These findings cast new light on conclusions of a previous Health Consultation by the US Agency for Toxic Substances and Disease Registry (ATSDR, 2004). That study concluded that, although plant emissions posed a real health risk, further health assessments would not be justified because of a lack of demonstrated DU exposure in the population. In contrast our method could provide estimates of the incidence and magnitude of DU aerosol inhalation exposure of the residential population, which is clearly important data for any follow-up study of potential health outcomes of the nearby population."

"Estimates of the initial inhalation dose of DU positive individuals range from up to 6 mg DU for residents to nearly 1 gram DU for workers....Given the variability in individuals and a probable variation in DU excretion of an individual from one day to the next, a considerable uncertainty exists for these calculated exposure estimates. However, their general magnitude falls into the Level II and Level I categories of exposure, respectively, referred to by the UK Royal Society (2001) and are sufficiently high to justify an investigation of the health implications in more detail and scope than has been undertaken to date."

"A comparison of these data with two recent larger testing programs of both UK veterans of the 1991 Persian Gulf conflict and the recent conflict in Iraq is revealing. In these UK studies of more than 800 individuals (DUOB, 2007; Bland et al., 2007) no DU-positive urine sample was found (the methods of analysis are largely comparable to those done in the Colonie study). In the case of Colonie where urinary DU is documented in exposed individuals after 25 years, the simplest conclusion is that if an individual is significantly exposed (i.e. Level II–Level I exposures; Royal Society, 2001), the urine isotope signature will persist for decades."

NL Industries Operation
"NLI was involved in the reduction of uranium tetra-fluoride to uranium metal, and fabrication of uranium articles from 1958–1984. These consisted mainly of DU projectiles, but with some enriched uranium for fuel rods prior to 1972..In 1979 the NYS Department of Environment investigated claims that the stack filters were bypassed, and subsequently forced the temporary closure of the plant for excessive emissions of uranium compounds to the atmosphere. A soil survey in 1980 found depleted uranium contamination within 600 m of the plant. The plant was permanently closed in 1984 and the property was transferred to the federal Department of Energy to remediate both the site and more than 50 contaminated nearby residential properties (ATSDR, 2004). The site has now been cleaned... by the U.S. Army Corps of Engineers, under the Formerly Utilized Sites Remedial Action Program."

Background on Depleted Uranium Use
"Depleted uranium (DU) is a by-product of the uranium isotope enrichment process, and has similar chemical toxicity to enriched or chemically purified natural uranium. When inhaled or ingested in sufficient doses, DU constitutes a distinct health hazard (Royal Society, 2001, 2002; WHO, 2001). DU has been used in military conflicts primarily as armor-penetrating munitions in the Persian Gulf conflict of 1991, the Balkans, and in Iraq primarily in 2003."

"Attempts to assess the significance of DU to health have been complicated in part by the lack of accurate exposure assessments, although it is clear that in laboratory experiments involving animals or cell cultures, high doses of DU induce cell damage and impair certain body functions. Although use of DU is acknowledged, the lack of evidence for substantial DU contamination of individuals via inhalation–ingestion has so far failed to clarify whether DU plays any role in Gulf War Illness. Recent studies appear to show that DU exposure may be uncommon to rare in military personnel, though it is uncertain whether and to what extent tested soldiers were exposed. The Colonie study is therefore important since it is a study of an exposed population with documented environmental aerosol contamination."

Science of the Total Environment (2007) (doi:10.1016/j.scitotenv.2007.09.044) 

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