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Rounds 1 and 2 Datasets for the Unregulated Contaminant Monitoring Program Managed by State Drinking Water Programs

State drinking water programs managed the original unregulated contaminant monitoring program that applied to public water systems (PWSs) serving more than 500 people.

The Round 1 dataset contains PWS monitoring results for 62 then-unregulated contaminants. These data were collected from 40 states and primacy entities between 1988 and 1992.

The Round 2 dataset contains PWS monitoring data for 48 then-unregulated contaminants. These data were collected from 35 states and primacy entities between 1993 and 1997.