Geology topics

Margaret J. Eggers

Publications and source records attributed to Margaret J. Eggers.

3 recordsLinked to original sources

USGS2026

Tapwater contaminant mixtures and cumulative risk screening on the Crow (Apsáalooke) Reservation

Introduction: Water insecurity is a challenge for the Apsáalooke (Crow) Tribal Nation in south-central Montana, United States. Both private-well and public-supply tapwater (TW) are vulnerable to a range of contaminants, posing potential risks to community health and well-being. Ongoing community concerns about unrecognized inorganic, organic, and microbial contaminants underscore the need for continued comprehensive monitoring and improved water management strategies. Materials and methods: TW samples were collected from 26 private-well and 12 public-supply participant locations, selected and recruited by the Crow Water Quality Project. A total of 35 inorganic, 450 organic, and three microbial analytes were assessed in these samples. Public-Supply Maximum Contaminant Levels and Health benchmark-based screening levels were used to evaluate contaminant concentrations. Results: Sixty-one organic and 34 inorganic contaminants were detected. Screening levels were frequently exceeded, particularly due to multiple inorganic contaminants in private TW and both chlorine-based disinfection byproducts (DBPs) and inorganics in public TW. These findings highlight gaps in current source-water protection and water treatment practices. Conclusions: After reporting results to participants, anonymized data were shared at community events to inform risk management decisions. The study underscores the importance of broad monitoring and analysis throughout the upper Missouri River basin and across the United States to address Tribal concerns over water insecurity and mitigate potential unrecognized TW contaminant risks, particularly to vulnerable subpopulations.

Montana↗

USGS2026

Per- and polyfluoroalkyl substances (PFAS) and other contaminants of concern in tribal waters of Montana

We assessed potential exposures to a broad suite of contaminants (inorganic, organic and microbial) in culturally important surface waters from three watersheds in a northern plains Native American community (Apsáalooke [Crow Tribe of Montana]) in south-central Montana, United States, with water insecurity concerns. Inorganic (37), organic (435) and microbial (3) constituents were assessed in 12 surface water sites from the Pryor Creek ( n = 2), Bighorn River ( n = 2) and Little Bighorn River ( n = 8) valleys. Twenty-six organics, 33 inorganics and Escherichia coli were detected. Despite relatively low concentrations in surface waters within the Crow Reservation, mixture toxicity indicated prevalent chronic ecological effects and human-health secondary contact (recreation) effects at multiple sites. Further, to address Tribal concerns over the prevalence and corresponding risks of per- and polyfluoroalkyl substances (PFAS), we sampled water, sediment, biofilms and fish at a limited number of locations in the Little Bighorn River. Results indicated that PFAS were prevalent in fish tissues, including whole blood and filets, and to a lesser extent in biofilms, despite few detections in water and sediment samples. This is the first attempt to document environmental PFAS contamination within the reservation and the potential human-health concerns for the general population from consumption of recreational/subsistence fish. Overall, this effort provided preliminary information on the contaminant mixtures present and their potential health implications, which can support the protection of community health and culturally meaningful resources across the Crow Reservation.

Montana↗

USGS2025

Statewide cumulative human health risk assessment of inorganics-contaminated groundwater wells, Montana, USA

Across the United States, rural residents rely on unregulated and generally unmonitored private wells for drinking water, which may pose serious health risks due to unrecognized contaminants. We assessed the nature, degree, and spatial distribution of cumulative health risks from inorganic contaminants in groundwater. Our analysis included nearly 84,000 data points from 6500+ wells, across 51 of Montana's 98 watersheds, using a public groundwater database. We compared a drinking water screening level cumulative risk assessment (CRA) for inorganics based on the U.S. Environmental Protection Agency (EPA) protective health thresholds (Maximum Contaminant Level Goals, Health Advisories [MCLG-HAs]) to a CRA based on EPA public supply enforceable Maximum Contaminant Levels (MCLs). Based on median concentrations of 19 inorganics (antimony, arsenic, barium, beryllium, boron, cadmium, chromium, copper, fluoride, manganese, molybdenum, nickel, nitrate, lead, selenium, strontium, thallium, uranium, zinc), 75% of watersheds had MCLG-HA-based cumulative risk values > 1.0; arsenic and uranium contributed the most risk, followed by strontium, fluoride, manganese and boron. Hence, this screening level (Tier I) CRA indicated widespread potential for unrecognized human health risk to private well users from inorganic contaminants considering both carcinogenic and non-carcinogenic risks. Sensitivity analysis showed that benchmarks applied (MCLG-HAs versus MCLs) exerted the largest control on results. Our findings identify priority regions for Tier 2 risk assessments to elucidate local sources and distributions of geogenic versus anthropomorphic contaminants. Our study is the first statewide assessment of cumulative health risk from groundwater that we are aware of, and results support increased statewide drinking water education and testing to reduce human health risks from contaminated private well water.

Montana↗