Study may shed new light on areas not previously thought to have arsenic issues in the groundwater

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A recent study by the U.S. Geological Survey and the CDC’s National Center for Environmental Health may shed new light on areas not previously thought to have arsenic issues in the groundwater.

Some 2.1 million Americans on domestic water wells may be at risk of harmful exposure to arsenic based on a national-scale predictive model detailed in the study, which shows areas potentially affected by arsenic levels greater than 10 parts per billion — the federally established maximum contaminant level.

The study’s top 10 states for people at risk for harmful arsenic exposure based on the size of the at-risk population are:

  1. Michigan, 192,747
  2. Ohio, 189,191
  3. Indiana, 150,858
  4. North Carolina, 119,633
  5. California, 115,823
  6. Maine, 102,452
  7. Texas, 95,455
  8. Pennsylvania, 80,729
  9. Minnesota, 80,353
  10. Wisconsin, 72,670.
The study abstract states: “Arsenic concentrations from 20,450 domestic wells in the U.S. were used to develop a logistic regression model of the probability of having arsenic >10 micrograms per liter (“high arsenic”) which is presented at the county, state, and national scales. Variables representing geologic sources, geochemical, hydrologic, and physical features were among the significant predictors of high arsenic.

“For U.S. Census blocks, the mean probability of arsenic >10 micrograms per liter was multiplied by the population using domestic wells to estimate the potential high-arsenic domestic-well population…. Although areas of the U.S. were underrepresented with arsenic data, predictive variables available in national data sets were used to estimate high arsenic in unsampled areas.

“Additionally, by predicting to all the conterminous U.S., we identify areas of high and low potential exposures in areas of limited arsenic data. These areas may be viewed as potential areas to investigate further or to compare to more detailed local information. Linking predictive modeling to private well use information nationally, despite the uncertainty, is beneficial for broad screening of the population at risk from elevated arsenic in drinking water from private wells.”

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