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Public health experts estimate that more than 200 million people worldwide are exposed to arsenic through contaminated drinking water. Scientists know long-term exposure to arsenic is associated with increased risk of chronic illnesses like cancer and cardiovascular disease, but there hasn't been a reliable way to track these exposures and fully understand their effects on the body and the mechanisms behind them.

A new study led by researchers at the University of Chicago addresses this challenge, shedding light on how arsenic leaves its mark on human DNA and offering a potential new tool for exposure assessment.…