Project 3: Modeling spatial patterns of metals and metal mixtures in drinking water in the US

Across the US, tens of millions of individuals unknowingly consume drinking water with concentrations of metals that exceed regulatory guidelines. The problem is more prominent in untreated water from private wells than in municipal drinking water supplies that undergo water treatment. Although private wells supply drinking water for more than 15% of the population, elevated concentrations of metals in these wells may go undetected and unremediated due to sporadic and incomplete monitoring data.  

map of well water locations in the USA

Our Goals

  • Develop a novel statistical method to identify populations potentially at risk for elevated exposures to metals through contaminated drinking water
  • Develop a map of metal mixtures characteristic of drinking water exposures in different regions
  • Investigate whether there are socioeconomic differences or disparities based on metal concentrations in drinking water

Our Approach

Project 3 is developing statistical models (based on logistic regression and random forest methods) to predict concentrations of metals and metal mixtures (arsenic, cadmium, and lead) in private wells based on 50 years of aggregated well data from the National Water Quality Monitoring Council, in addition to  information about hydrological and geological features associated with metal occurrence.

In addition, together with the Environmental Working Group, we are examining decades of public water supply records in combination with information on point sources and indicators of socioeconomic disparities to determine whether elevated concentrations of metals in public drinking water supplies are associated with indicators of environmental justice. 

Project 3 Team

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Recent Publications

Mayuri Bhatia, Aaron J Specht, Vallabhuni Ramya, Dahy Sulaiman, Manasa Konda, Prentiss Balcom, Elsie M Sunderland, and Asif Qureshi. 2021. “Portable X-ray Fluorescence as a Rapid Determination Tool to Detect Parts per Million Levels of Ni, Zn, As, Se, and Pb in Human Toenails: A South India Case Study.” Environ Sci Technol, 55, 19, Pp. 13113-13121. Publisher's VersionAbstract
Chronic exposure to inorganic pollutants adversely affects human health. Inductively coupled plasma mass spectrometry (ICP-MS) is the most common method used for trace metal(loid) analysis of human biomarkers. However, it leads to sample destruction, generation of secondary waste, and significant recurring costs. Portable X-ray fluorescence (XRF) instruments can rapidly and nondestructively determine low concentrations of metal(loid)s. In this work, we evaluated the applicability of portable XRF as a rapid method for analyzing trace metal(loid)s in toenail samples from three populations (n = 97) near the city of Chennai, India. A Passing-Bablok regression analysis of results from both methods revealed that there was no proportional bias among the two methods for nickel (measurement range ∼25 to 420 mg/kg), zinc (10 to 890 mg/kg), and lead (0.29 to 4.47 mg/kg). There was a small absolute bias between the two methods. There was a strong proportional bias (slope = 0.253, 95% CI: 0.027, 0.614) between the two methods for arsenic (below detection to 3.8 mg/kg) and for selenium when the concentrations were lower than 2 mg/kg. Limits of agreement between the two methods using Bland-Altman analysis were derived for nickel, zinc, and lead. Overall, a suitably calibrated and evaluated portable XRF shows promise in making high-throughput assessments at population scales.
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