Compared
MCL vs. MCLG
An MCL (maximum contaminant level) is the highest amount of a contaminant allowed in drinking water, and it is legally enforceable. An MCLG (maximum contaminant level goal) is the level with no known health risk, a non-enforceable target. The MCL is set as close to the MCLG as treatment can feasibly reach.
Last reviewed 2026-08-04
| MCL | MCLG | |
|---|---|---|
| What it is | A legal limit | A health goal |
| Enforceable? | Yes | No |
| Based on | Health plus what treatment can feasibly reach | Health only, with a safety margin |
| Typical value | Set as close to the MCLG as feasible | Sometimes zero for certain contaminants |
The bottom line
The MCLG is the ideal target; the MCL is the enforceable rule, set as close to that ideal as treatment allows.
Common questions
- Which one is the law?
- The MCL. The MCLG is a goal, not an enforceable limit.
- Can an MCLG be zero?
- Yes, for some contaminants the health goal is zero, even though the MCL is a small allowed amount.
- Why are they different?
- The goal is health-only; the limit also weighs what treatment can realistically achieve.