Frequent Questions

What do MCL, MCLG and MRDL mean?

MCL:

Maximum contaminant level: the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to the maximum contaminant level goals as feasible using the best available treatment technology.

MCLG:

Maximum contaminant level goal: the level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety.

TT:

Treatment technique: a required process intended to reduce the level of a contaminant in drinking water.

AL:

Action level: the concentration of a contaminant which, if exceeded, triggers treatment or other requirements which a water system must follow.

Variances and Exemptions:

State or EPA permission not to meet an MCL or a treatment technique under certain conditions.

MRDLG:

Maximum residual disinfection level goal. The level or a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.

MRDL:

Maximum residual disinfectant level. The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

MNR:

Monitored not regulated.

MPL:

State assigned maximum permissible level.

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