The goal, and the limit.
The health goal
Not enforceableEPA defines it as "the level of a contaminant in drinking water below which there is no known or expected risk to health." EPA calls these "non-enforceable public health goals."
The legal limit
EnforceableThe highest level of a contaminant allowed in drinking water. EPA says MCLs are "set as close to MCLGs as feasible," using the best available treatment technology and taking cost into consideration.
Definitions from EPA, National Primary Drinking Water Regulations · page last updated Aug 31, 2026
Sometimes equal. Sometimes not.
Three rows from EPA's regulation table, copied as listed (milligrams per liter):
| Contaminant | Health goal (MCLG) | Legal limit (MCL) | Same? |
|---|---|---|---|
| Nitrate (as nitrogen) | 10 | 10 | Yes |
| Arsenic | 0 | 0.010 | No |
| Benzene | zero | 0.005 | No |
Values from EPA, National Primary Drinking Water Regulations table, as listed on Oct 9, 2026
A health goal of zero means EPA's goal is none of that contaminant at all. The legal limit is then set as close to that goal as EPA judges feasible.
And then there are advisories.
For some contaminants that don't have national regulations, EPA publishes health advisories instead. They cover exposure periods "(e.g., 1 day, 10 days, a lifetime)" and, as EPA says, are not legally enforceable standards.
Summary of EPA, Drinking Water Health Advisories (HAs)
What this does not mean.
- that water between the health goal and the legal limit is unsafe for everyone
- that "in compliance" water is bad, or that your water is out of compliance
- that every contaminant has both numbers; many have only one, or none
It does show that "legal" and "EPA's health goal" can be different numbers, and the gap is worth knowing about for your own water.
- EPA · National Primary Drinking Water RegulationsPage last updated Aug 31, 2026 · quotes + table values · Last checked Oct 9, 2026
- EPA · Drinking Water Health Advisories (HAs)Page last updated Mar 30, 2026 · quote + summary · Last checked Oct 9, 2026
Plain-English summaries are ours. Words in quotation marks were checked word for word against the agency page on Oct 9, 2026. Links go to the agency's own site. EPA and USGS do not endorse this site or any product. This is general education, not medical advice.