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

Abstract

More than 500 unreclaimed mines and associated waste sites exist on the Navajo Nation reservation as a result of uranium (U) mining from the 1940s through the 1980s. For this study, the impact of U-mine waste on a common, locally grown crop food was examined. The goal of this site-specific study was to determine metal(loid) concentration levels of arsenic (As), cadmium (Cd), cesium (Cs), molybdenum (Mo), lead (Pb), thorium (Th), U, vanadium (V) and selenium (Se) in Cucurbita pepo Linnaeus (squash), irrigation water, and soil using inductively coupled plasma-mass spectrometry. The concentrations of metal(loid)s were greatest in roots > leaves > edible fruit (p < 0.05), respectively. There were significant differences between metal(loid)s in squash crop plot usage (<5 years versus >30 years) for V (p = 0.001), As (p < 0.001), U (p = 0.002), Cs (p = 0.012), Th (p = 0.040), Mo (p = 0.047), and Cd (p = 0.042). Lead and Cd crop irrigation water concentrations exceeded the United States Environmental Protection Agency (USEPA) Maximum Contaminant Levels for drinking water for those metals. Edible squash concentration levels were 0.116 mg/kg of As, 0.248 mg/kg of Pb, 0.020 mg/kg of Cd, and 0.006 mg/kg of U. Calculated human ingestion of edible squash did not exceed Provisional Tolerable Weekly Intake or Tolerable Upper Limit levels from intake based solely on squash consumption. There does not appear to be a food-ingestion risk from metal(loid)s solely from consumption of squash. Safer access and emphasis on consuming regulated water was highlighted. Food intake recommendations were provided. Continued monitoring, surveillance, and further research are recommended.

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].…”

“…As such, the RDI and RDA requirements may have been met in this study sample by the combination of tea ingestion and other foods consumed, however, this study exclusively focused on one harvested food item of the entire diet. 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].…”

“…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.…”

“…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].…”

Selenoproteins and their emerging roles in signaling pathways

“…Cadmium (Cd) is a ubiquitous and non-biodegradable pollutant representing a great concern to human health. High Cd exposure has been reported among workers in the construction and manufacturing industries such as mining for metals or in the manufacture of pigments and batteries (Samuel-Nakamura et al, 2019). In the general population, the main sources of exposure are food, cigarette smoking, inhalation of ambient air, drinking water, contaminated soil or dust (Rinaldi et al, 2017).…”