What Is an MCLG? The Health Goal Behind Water Limits

The MCLG is the “ideal” column in your water quality report. It tells you the level the EPA would aim for if health were the only consideration. The number your utility actually has to meet is the one next to it: the MCL, or for lead and copper, the action level.

Why is the MCLG for some contaminants zero?

It depends on what the contaminant does. According to the EPA’s explanation of how it sets drinking water standards:

• Germs (bacteria, viruses, protozoa) get a goal of zero, because swallowing a single one may cause illness.
• Chemicals that may cause cancer get a goal of zero when there is no dose below which the chemical is considered safe. If a safe dose can be identified, the goal is set above zero.
• Other chemicals get a goal based on a daily dose not expected to harm health over a lifetime, divided by safety factors that account for sensitive groups such as infants, children and older adults.

That’s why lead, arsenic and benzene have goals of zero, and so do PFOA and PFOS under the 2024 PFAS rule. For lead, the EPA states on its Lead and Copper Rule Improvements page that there is no safe level of exposure. Nitrate (10 ppm) and copper (1.3 ppm) have goals above zero, matching their enforceable numbers.

If the goal is zero, is my water unsafe?

Not necessarily. Because the goal ignores cost and what treatment can achieve, the EPA notes that some goals are set at levels water systems can’t meet. A goal of zero means no amount is known to be risk-free, so less is better; it doesn’t mean a result under the legal limit will make you sick.

What it does mean is that “meets the standard” and “matches the goal” can be two different things. If a contaminant with a zero goal shows up in your water and you’d rather reduce it, that’s a reasonable choice. Start with the exact number, then look at certified options. Lead from home plumbing is the most common case; our lead guide covers testing and filters.

Where do I see the MCLG in my water report?

Every water quality report must print the MCLG definition in the EPA’s words, and the results table puts the MCLG next to the MCL, in the same units. Our guide to reading your water quality report explains each column. As of October 10, 2026, lead’s goal is zero and its action level is 15 ppb, dropping to 10 ppb on November 1, 2027.