11. Louisville, KY
Contaminants detected above health guidelines: 6
Around 764,769 consumers get water from the Louisville Water Company, and even though it has six contaminants which are exceeding allowed limits, this is still one of the cities with the cleanest tap water in the US. Those harmful chemicals are chlorite, chromium, perfluorinated chemicals, radiological contaminants, trihalomethanes, and hormones.
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