National Water-Quality Assessment (NAWQA) Program
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Figure 15. Mixtures of two or more contaminants were detected at concentrations greater than one-tenth of individual human-health benchmarks in 84 percent of samples, and mixtures of five or more contaminants were detected at such concentrations in 17 percent of samples. Little is known about the potential health effects associated with exposure to contaminant mixtures. Data are from 383 source-water samples from public wells in which major ions, trace elements, nitrate, radon, pesticide compounds, and volatile organic compounds were analyzed. ≥, greater than or equal to.