New Mexico Geological Society Annual Spring Meeting — Abstracts

From 1952-1982, uranium ores were mined extensively at numerous mine sites in the Southwest USA, a significant number on them on Native American Tribal Lands. During their periods of operation, these mines caused significant health hazards both to miners and the communities living in close proximity to the mine sites. Although these mines are now shut down, the environmental legacy of mining continues to be of major concern to the local communities. Although some of these abandoned uranium mines (AUM) sites have been reclaimed under the US EPA Superfund program, many have not. The potential exposures to uranium through water, air, and food sources, such as livestock, even from reclaimed mines are still poorly understood. In particular, the potential past and present risks of exposure to toxic metals by inhalation of airborne particles derived from contaminated soils and mine wastes from AUM is essentially unknown. New research is underway to assess the concerns of Native American communities living close to the recently designated Superfund Sites at Blue Gap/Tachee in Arizona and at Laguna Pueblo in New Mexico. The research is supported by the newly-established University of New Mexico’s Metal Exposure Toxicity Assessment on Tribal Lands in the Southwest (METALS) Superfund Research Project funded by the National Institute of Environmental Health Sciences.

The overall goal of the research is to determine if wind-blown, re-suspended particulate matter (PM) from these two AUM sites is a potential pathway for human exposure to toxic metals, such as uranium, vanadium, arsenic, and copper. In particular, the <2.5 micron PM size fraction is especially hazardous to human health because it is respirable and retained deep in the lungs when inhaled. We are investigating this problem using both laboratory experiments and in situ sampling of airborne particulates from the mine sites. Soil and mine waste samples from the mine sites undergo laboratory resuspension following initial sieving into coarse-size fractions and SEM characterization. Resuspension is carried out using a cascade impactor collector to separate the dust into different fine-grained size fractions. These different fractions are analyzed in detail using SEM and TEM techniques and ICP-MS to define the chemical, physical, and mineralogical characteristics of the metal mixtures. This work provides a characterization of the key characteristics of the local source materials which may undergo aeolian transport. We especially want to understand if toxic metals are present within these source materials as nanoparticles that would be highly reactive in lung fluids if inhaled and could result in a low level, constant exposure to these metals.

These data will then be integrated with similar analyses of airborne particulates collected from the mine sites to develop a more complete understanding of potential toxic metal exposures for communities downwind of the mine sites. The results of the study will better quantify and understand the exposure risks associated with airborne particulates. The data are critical to developing more effective exposure mitigation strategies for at-risk communities, such as an early warning system initiated by specific wind direction and/or velocity conditions.