Integrated risk assessment of groundwater contamination and respiratory outcomes in mining-impacted regions: A case study of Picher, Oklahoma

Background: Groundwater contamination from legacy mining remains a critical but underexamined threat to public health in many former mining communities in the United States. This study investigates the spatial distribution of heavy metals in groundwater and assesses the associated respiratory health risks in the mining-impacted town of Picher, Oklahoma—part of the Tar Creek Superfund area. Methods: Thirty groundwater samples were collected from residential wells and boreholes across ten neighborhoods and analyzed for lead (Pb), cadmium (Cd), arsenic (As), manganese (Mn), and zinc (Zn) using atomic absorption spectrophotometry. Exposure assessment followed USEPA models for ingestion and dermal pathways, with risk characterization using Chronic Daily Intake (CDI), Hazard Quotient (HQ), and Hazard Index (HI) metrics. Household surveys (n = 360) and spirometry testing (n = 180) were conducted to evaluate respiratory health outcomes. Spatial interpolation and regression analyses were performed using ArcGIS and QGIS platforms. Monte Carlo simulation modeled exposure uncertainty over 10,000 iterations. Results: Pb and Cd concentrations exceeded WHO and EPA limits in over 85% of sampled wells, with the highest levels observed in the eastern and southern sectors of Picher. HI values exceeded 4.0 in several neighborhoods, with ingestion representing the dominant exposure pathway. Monte Carlo analysis produced a 95th percentile HI of 7.1, highlighting severe population-level exposure risk. Spatial correlations were observed between high-HI zones and respiratory morbidity, including reduced FEV1 and FVC values. Adults aged 25–64 and children were the most affected, due to occupational exposure and physiological vulnerability, respectively. Conclusion: This study establishes a strong association between groundwater heavy metal contamination and respiratory health risks in the post-mining community of Picher, Oklahoma. The findings emphasize the urgent need for groundwater remediation, targeted health surveillance, and environmental justice policies. The study also proposes an interdisciplinary framework integrating hydrochemical, geospatial, and epidemiological tools to inform risk mitigation in similar post-industrial settings.