The work of research hydrologist Melissa Lombard, of the USGS New England Water Science Center, ties contaminant occurrence in groundwater with human health effects. Her previous research on arsenic has contributed to several studies by Maya Spaur during her doctoral studies at Columbia University. The most recent of these analyses looked at associations between inorganic arsenic in drinking water and concentrations of arsenic found in urine.

Inorganic arsenic is a toxic contaminant and known carcinogen. Continual exposure to inorganic arsenic increases the risk of cancer and other chronic diseases. Therefore, understanding its presence in drinking water sources will inform requisite drinking water regulations and interventions in communities that need to reduce arsenic exposure.

In 2021, Lombard developed machine learning models of arsenic in private wells throughout the United States as a means to assess arsenic exposure in human health studies. This study was a part of a cooperative project out of the USGS John Wesley Powell Center for Analysis and Synthesis that includes federal and university scientists. The project is investigating the health effects of arsenic exposure from private and public wells by linking environmental and public health data.

“These collaborations between hydrologists who understand the arsenic data, and epidemiologists who understand the human health data produce very robust studies,” said Lombard. “The role I play [in these studies] is to ensure that Maya's use and interpretation of the groundwater arsenic occurrence data is correct.” 

In addition to Lombard’s predictive models of arsenic concentration exceedances in private wells, a public water supply dataset of actual arsenic concentrations was created by Annie Nigra, an environmental health sciences assistant professor at Columbia University, using data from the U.S. Environmental Protection Agency’s Contaminants Occurrence Database.

Lombard served as Spaur’s mentor for her Superfund Research Program KC Donnelly internship where they produced their first paper using Lombard’s model, which evaluated arsenic concentrations in the United States among private well water and community water supplies. Since then, Lombard has continued to mentor and collaborate with Spaur.

Published in Environmental Research, Spaur’s most recent study using Lombard and Nigra’s datasets is the first nationwide investigation to determine how drinking water contributes to arsenic exposure in private wells and community water systems. Looking at associations between drinking water arsenic and inorganic arsenic biomarkers in urine, Spaur found that arsenic in drinking water is associated with contaminant levels in the general U.S. population. The higher the amount of arsenic in the drinking water, whether public or private, the higher the concentrations of inorganic arsenic in the urine.

“This is pretty striking because private wells aren’t regulated and community water systems are, but we found very similar associations between both of them,” Spaur said. “The findings suggest that communities are still being exposed to inorganic arsenic, and that is being reflected in urinary biomarkers, even when their public water systems are in compliance with the maximum contaminant level of their state or with the federal standard, which is 10 micrograms per liter.”

For private wells, Spaur found a positive trend between arsenic in drinking water and in urinary biomarkers in the Northeast. Parts of the Northeast have high arsenic concentrations in groundwater. Contrarily, many community water systems in New England rely on surface water containing low levels of arsenic. This finding reinforces the elevated role private wells in the Northeast play in arsenic exposure compared to the region’s public water systems, and the study recommends well-water testing in areas with high arsenic in the groundwater.

“Lombard and [USGS Supervisory Hydrologist Joseph] Ayotte were instrumental in not only helping me describe how the private well-water was formed, but really in interpreting and providing context, especially when you’re looking at geographic differences in our findings,” Spaur said. “They really helped bring a perspective in how these geographic differences reflect what we know about geological and hydrological differences in groundwater arsenic across the country.”

Spaur will continue to use Lombard’s data to find connections between urinary arsenic and drinking water arsenic as a means to inform public health regulations and to study exposure-disease associations.