A new comprehensive analysis spanning over three decades sheds light on the growing presence of geogenic contaminants in the groundwater that serves as drinking water for nearly 150 million people in the United States. Published by the U.S. Geological Survey (USGS), the study, which covers data from 1988 to 2022, presents crucial insights for water-resource managers and public health professionals to address potential risks associated with well water contaminants and their mixtures.
Groundwater, particularly from aquifers, is a primary source of drinking water. However, its safety can be compromised by the presence of geogenic contaminants, naturally occurring elements released into water through interactions between groundwater and rock formations. While some of these contaminants, like manganese, molybdenum, and sulfate, are essential in small amounts, elevated levels can lead to severe health issues, including organ damage, cancer, and reproductive harm.
Between 1988 and 2022, the study revealed that elevated concentrations of these contaminants were widespread across the United States. Among the most commonly detected contaminants in groundwater wells were arsenic, lithium, radium, sulfate, and uranium. Elevated levels are particularly concerning for the 37 million Americans who rely on domestic wells for drinking water, as these wells are typically unregulated, leaving individuals responsible for monitoring and treating their water. The research covered groundwater quality for approximately 5 million people, with over 2.3 million domestic well users potentially exposed to harmful levels of one or more contaminants.
The research covered groundwater quality for approximately 5 million people, with over 2.3 million domestic well users potentially exposed to harmful levels of one or more contaminants
The study found that rising concentrations of contaminants were more common than declines, with trends varying based on aquifer type, constituent geochemistry, well depth, land use, and regional influences. For instance, elevated chloride levels in the northeastern U.S. were linked to road salt usage, while in the western U.S., evaporative processes contributed to the rise in chloride concentrations.
Many domestic well networks reported elevated levels of contaminants affecting populations of 90,000 or more people. For example, concentrations of lithium, manganese, radium, and uranium were found to increase over time, whereas fluoride and molybdenum levels remained relatively stable. Notably, mixtures of multiple contaminants were frequently detected, indicating a potentially emerging health risk. This is particularly concerning as current human-health guidelines do not account for the effects of combined contaminant exposure, leaving an essential gap in understanding the cumulative health risks.
While increasing trends were more common, there were signs of stability in certain areas. For example, fluoride concentrations remained low at most sites, with only one well network showing significant increases. Excessive fluoride can damage bone health at high concentrations, but this was a less pressing concern in the study's findings.
Human activity also plays an important role in altering groundwater quality. Groundwater extraction, land-use changes, and agricultural practices can shift the geochemical makeup of aquifers. In California’s San Joaquin Valley, for instance, agricultural irrigation has led to the migration of uranium-contaminated groundwater into deeper aquifers, raising concerns for water quality in arid regions.
