A new study by the U.S. Geological Survey and the Centers for Disease Control and Prevention estimates about 2 million Americans may be getting their drinking water from private wells considered to have high concentrations of arsenic.
The nationwide study suggests that those on private wells, including people in New Jersey, should consider having their water tested for the contaminant, presumed to be coming from natural sources.
Some of the locations where it is estimated that most people may have high levels of arsenic in their private wells include much of the West, parts of the Northeast, including New Jersey, and some of the southeastern coastal states.
“About 44 million people in the lower 48 states use water from domestic wells,’’ said Joe Ayotte, a USGS hydrologist and lead author of the study. “While we’re confident our research will help well owners understand if they live in areas of higher risk for arsenic, the only way for them to be certain of what’s in their water is to have it tested.’’
The study is the latest by the USGS to look at potential problems with private wells. This summer, it found untreated groundwater in New Jersey shows high potential for being corrosive, increasing the risk for water coming out of the taps of homeowners with private wells.
Approximately 1 million people depend on private wells for their drinking water, according to the study. Long-term exposure to arsenic may cause health-related problems, including an increased risk of cancer.
In the arsenic study, using a standard of 10 micrograms per liter — the maximum contaminant level allowed for public water supplies — the researchers developed maps of the contiguous United States, showing locations where there are likely higher levels of arsenic in groundwater and how many people may be using it.
Nearly all of the arsenic in the groundwater tested for this study and used to map probabilities is likely from natural sources, and is presumed to be coming primarily from rocks and minerals through which the water flows.
In New Jersey, the areas with the highest concentrations appear to be in the northern Piedmont region of the state, according to Ayotte. The study ranked New Jersey 20th in population exposed to arsenic concentrations nationwide.
Using water samples from more than 20,000 domestic wells, the researchers developed a statistical model that estimates the probability of high arsenic in domestic wells in a specific area. They used that model in combination with information on the U.S. domestic well population to estimate the population in each county of the continental United States with potentially high concentrations of arsenic in wells.
Ayotte cautioned that while the study provides state and county estimates, they are not intended to take the place of more detailed or local information that may be available.