The U.S. counties with the most egregious water quality violations are concentrated in four states: West Virginia, Pennsylvania, North Carolina and Oklahoma, a new study has found.

Standing out among the top-10 such regions was Wyoming County, W. Va., whose public water utility boasted the highest number of infringements in a single water system, according to the study, published Tuesday in international journal Risk Analysis.

About 2 million people nationwide — equivalent to Nebraska’s entire population — do not have running water, and this lack of basic drinking water services tends to occur in clusters, the study authors determined.

“This high number is neither equally nor proportionally distributed across the population,” they wrote.

With another 30 million people reliant on

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