Uranium and Associated Heavy Metals in Ovis aries in a Mining Impacted Area in Northwestern New Mexico

Abstract

The objective of this study was to determine uranium (U) and other heavy metal (HM) concentrations (As, Cd, Pb, Mo, and Se) in tissue samples collected from sheep (Ovis aries), the primary meat staple on the Navajo reservation in northwestern New Mexico. The study setting was a prime target of U mining, where more than 1100 unreclaimed abandoned U mines and structures remain. The forage and water sources for the sheep in this study were located within 3.2 km of abandoned U mines and structures. Tissue samples from sheep (n = 3), their local forage grasses (n = 24), soil (n = 24), and drinking water (n = 14) sources were collected. The samples were analyzed using Inductively Coupled Plasma-Mass Spectrometry. Results: In general, HMs concentrated more in the roots of forage compared to the above ground parts. The sheep forage samples fell below the National Research Council maximum tolerable concentration (5 mg/kg). The bioaccumulation factor ratio was >1 in several forage samples, ranging from 1.12 to 16.86 for Mo, Cd, and Se. The study findings showed that the concentrations of HMs were greatest in the liver and kidneys. Of the calculated human intake, Se Reference Dietary Intake and Mo Recommended Dietary Allowance were exceeded, but the tolerable upper limits for both were not exceeded. Food intake recommendations informed by research are needed for individuals especially those that may be more sensitive to HMs. Further study with larger sample sizes is needed to explore other impacted communities across the reservation.

Occurrence and Risk of Metal(loid)s in Thelesperma megapotamicum Tea Plant

“…The overall U concentration levels were the lowest in all aboveground tea parts and root categories, except in root soil and topsoil (it was the third and fourth lowest in the latter categories). Generally, smaller U concentrations levels were demonstrated in squash crop, but greater metal(loid) concentrations (As, Pb, Se, and U) were seen in seven species of aboveground sheep forage plants, root, and soil in the parent study [22,24].…”

“…Tea and environmental sample preparation and analysis have been reported in detail in previous publications [22][23][24]. Field samples were stored in a −20 • C freezer before sample preparation and analyses.…”

“…In the parent cohort, varying findings were found with Mo and Se whereby squash did not meet the Mo RDA and Se RDI [24]. However, both micronutrients were exceeded in sheep meat by 205% (Mo RDA) and 713% (Se RDI) [22]. It is advisable to consider all foods consumed collectively to avoid exceedances above the UL.…”

“…The U mining era occurred from the 1940s to the 1980s [21]. Hard rock mining areas are a problem in this and other AI communities with more than 160,000 mining sites existing [21] in the western U.S. Mining impacted areas on Diné lands have a potential to effect food resources as demonstrated by several reports on harvested herbs, forage plants, crops, meat, soil and water [22][23][24].…”

Metal(loid)s in Cucurbita pepo in a Uranium Mining Impacted Area in Northwestern New Mexico, USA

“…Metal and metalloid contamination may occur in uranium (U)-mining-impacted areas [1,2,3,4], particularly in agricultural areas [5,6] where metals can migrate into the food chain from anthropogenic sources. The history of U mining on Navajo (Diné) lands began in the 1940s and continued through the 1980s; a considerable legacy of waste remains.…”