Exposure Pathways and Health Effects Associated with Chemical and Radiological Toxicity of Natural Uranium: A Review

Abstract

Natural uranium exposure derives from the mining, milling, and processing of uranium ore, as well as from ingestion of groundwater that is naturally contaminated with uranium. Ingestion and inhalation are the primary routes of entry into the body. Absorption of uranium from the lungs or digestive track is typically low but can vary depending on compound specific solubility. From the blood, two-thirds of the uranium is excreted in urine over the first 24 hours and up to 80% to 90% of uranium deposited in the bone leaves the body within 1.5 years. The primary health outcomes of concern documented with respect to uranium are renal, developmental, reproductive, diminished bone growth, and DNA damage. The reported health effects derive from experimental animal studies and human epidemiology. The Lowest Observed Adverse Effect Level (LOAEL) derived from animal studies is 50 microg/m3 for inhalation and 60 ug/kg body weight/day for ingestion. The current respiratory standard of the Occupational Safety and Health Administration (OSHA), 50 microg/m3, affords no margin of safety. Considering the safety factors for species and individual variation, the ingestion LOAEL corresponds to the daily consumption set by the World Health Organization Drinking Water Standard at 2 microg/L. Based on economic considerations, the United States Environmental Protection Agency maximum contaminant level is 30 microg/L. Further research is needed, with particular attention on the impact of uranium on indigenous populations, on routes of exposure in communities near uranium sites, on the combined exposures present at many uranium sites, on human developmental defects, and on health effects at or below established exposure standards.

Biosorption of metal and salt tolerant microbial isolates from a former uranium mining area. Their impact on changes in rare earth element patterns in acid mine drainage

“…For all investigated strains U, Cu and La possess the highest toxicity. U is both chemo-and radiotoxic to biota and causes, amongst others, DNA damage [5]. Copper is known to belong to the group of metals that expose high toxicity towards many bacterial taxa, although essential as cofactor in tiny amounts [30].…”

Lessons from the Navajo: Assistance with Environmental Data Collection Ensures Cultural Humility and Data Relevance

“…The prevalence of kidney disease maybe attributable to the nephrotoxic effects of uranium [7][8][9] resulting from occupational and environmental exposures. Community activism raised awareness of the potential public health impacts of uranium exposure, prompting the Eastern Navajo Health Board to seek assistance from a multidisciplinary partnership to address concerns about uranium as a potential kidney toxin in 22 Navajo chapters (similar to towns).…”

Potential Health Risks from Uranium in Home Well Water: An Investigation by the Apsaalooke (Crow) Tribal Research Group

“…Other national and international standards for uranium in drinking water are stricter. In Canada, the "maximum acceptable concentration" is 20 μg/L [65], which was the standard initially proposed for the U.S. EPA, but rejected based on a cost-benefit analysis [45]. Some states, such as Vermont, have also opted for the more conservative standard of 20 μg/L [5].…”

“…Exposure can increase cancer risk and lead to liver damage [44]. Additional documented health outcomes of concern include effects on the brain, diminished bone growth, DNA damage and developmental and reproductive effects [45,46]. The health risks from uranium in drinking water are greatest for infants and young children, who can suffer lasting damage from exposure at critical times in their growth [47].…”