Frequent Questions

On January 22, 2001, EPA published a final rule lowering the arsenic maximum contaminant level from 50 ppb (parts per billion) to 10 ppb (66 FR 6976). Is the MCL based on total arsenic or inorganic arsenic?

The MCL for arsenic in drinking water is based on total arsenic including both organic and inorganic forms (66 FR 6976, 7046; January 22, 2001).

Additional information on arsenic is available at
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