— 1979 Church Rock Uranium Mill disaster, New Mexico — worst U.S. accident, ongoing contamination (VIDEO)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1963288/

“In the early morning hours of July 16, 1979, less than 4 months after the highly publicized release at Three Mile Island,32 the earthen dam at Church Rock Mill failed (Table 1). The amount of radiation released at United Nuclear Corporation was larger than the release at Three Mile Island. The 6-m-wide dam breach sent approximately 1100 tons of radioactive mill waste and 95 million gallons of mine process effluent down Pipeline Arroyo and into the North Fork of the Puerco River.33 This tremendous flow of water backed up sewers, affected 2 nearby aquifers, left pools along the river, and transported contaminants 130 km downstream to a point near Navajo, Arizona.34

With the exception of the 6-person human exposure assessment carried out by the Centers for Disease Control and Prevention,33 the various exposure pathways and related human health outcomes associated with this spill have yet to be characterized. The Centers for Disease Control study addressed only inhalation of suspended tailings and ingestion of livestock, ruling out other exposure pathways such as consumption of vegetables, ingestion of river water or groundwater, and inadvertent ingestion of contaminated sediment. This assessment failed to incorporate not only all potential exposures but also radiation types.34 A number of subsequent studies carried out in the Puerco River basin have identified contaminated groundwater from the spill as well as downstream transport and deposition of radionuclides from the Pipeline Arroyo areas, suggesting that exposure will continue to occur through these pathways in the future.3537

Like Sequoyah Fuels Corporation, the Church Rock spill occurred in a low-income, rural, American Indian area, albeit closer to a substantial secondary city, Gallup, NM, which has large Hispanic and White populations. Because the spill happened in the immediate aftermath of nationwide coverage of the Three Mile Island release, the muted coverage and response is particularly striking. It is not clear that there was acute harm from the Church Rock spill, so like Three Mile Island, the main concern is the development of disease over time after exposure. Compared with Sequoyah Fuels Corporation, the Church Rock spill contained more radioactivity because the tailings included radium, thorium, and other uranium decay products that have relatively high specific activities. In contrast to Three Mile Island, the population near Church Rock was already chronically exposed to uranium mine and mill waste through both occupational and environmental routes and continues to be exposed today.38

A series of local struggles and public health studies have refocused local attention on the Church Rock area as well as the entire Eastern Navajo area. The struggles revolve around proposals to restart uranium mining with in situ leach methods. In response, the Navajo Nation voted to ban all uranium mining, a resolution that is currently being challenged by mining companies.39 The studies are community based and involve a collaboration among Eastern Navajo communities, the Southwest Research and Information Center, the University of New Mexico, and others. The focus of research is the health impact of environmental uranium exposure (oral communication, J. Lewis, PhD, University of New Mexico, and C. Shuey, MPH, Southwest Research and Information Center, March–June 2006)…”

Brugge, D., deLemos, J. L., & Bui, C. (2007). The Sequoyah corporation fuels release and the Church Rock spill: unpublicized nuclear releases in American Indian communities. American journal of public health97(9), 1595–1600. https://doi.org/10.2105/AJPH.2006.103044