Frequent Questions

What is the relative source contribution (RSC) with regard to development of drinking water standards?

The RSC represents the portion of an individual?s daily exposure to a contaminant attributed to drinking water. Individuals can be exposed to a contaminant through sources other than drinking water, such as food or air. EPA accounts for these other contributions when calculating the maximum contaminant level goal by incorporating the RSC into the calculation (54 FR 22062, 22069; May 22, 1989). Additional information on standard setting is available at
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