Frequent Questions

What is the difference between a maximum contaminant level goal (MCLG) and a reference dose (RfD)?

The maximum contaminant level goal (MCLG) means the maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, and which allows an adequate margin of safety. Maximum contaminant level goals are non-enforceable health goals (40 CFR 141.2). The MCLG is derived in a three-step process that includes the calculation of a Reference Dose (RfD). The (RfD) is an estimate of the amount of a chemical that a person can be exposed to on a daily basis that is not anticipated to cause adverse systemic health effects over the person's lifetime (Seminar Publication: Risk Assessment Management and Communication of Drinking Water Contamination, EPA625-4-89-024).
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