Maximum Contaminant Level Goal (MCLG)
The level of a contaminant in drinking water below which there is no known or expected health risk — a non-enforceable goal that is often stricter than the enforceable MCL.
How It Works
MCLGs are set by the EPA based purely on health considerations, without regard to cost or technical feasibility. For carcinogens (cancer-causing agents), the MCLG is typically set at zero — meaning any exposure carries some theoretical risk. The MCLG for lead is zero. The MCLG for PFOA is zero. However, the enforceable MCL may be higher than zero because removing a contaminant to absolutely zero is technically impossible or prohibitively expensive. The gap between the MCLG and the MCL represents a pragmatic compromise between ideal health protection and real-world constraints.
Related Terms
- Maximum Contaminant Level (MCL) — The highest level of a contaminant allowed in drinking water — set by the EPA and enforceable by law. Exceeding the MCL triggers a health-based violation.
- Health-Based Violation — The most serious type of drinking water violation — indicating that water quality has exceeded a maximum contaminant level or failed to meet a treatment requirement that directly protects health.
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About This Definition
This definition is part of the IsWaterSafe Drinking Water Safety Glossary — 22 terms explaining water contaminants, treatment methods, and safety standards. Written for homeowners, renters, journalists, and public health professionals.