Most homeowners on public water read the annual quality report once, scan a column of mostly clean results, and file it away. A study covered by Circle of Blue on October 23, 2026, gives you a good reason to read that page more slowly. Its headline says PFAS contamination in drinking water "may be underestimated," and the piece, by Alissa de Chassey, first appeared at Inside Climate News. The focus is on results that fall below laboratory reporting limits, which is exactly where a clean-looking report can mislead. You can read the full coverage at Circle of Blue's report on underestimated PFAS levels in drinking water.
Why a Blank Is Not Always a Zero
Every lab sets a reporting limit, the lowest concentration it will report as a number with confidence for a given test method. Below that line, a result may read "not detected" or appear with a symbol such as ND or a flag saying the value is below the limit. That wording tells you the lab could not quantify the compound at that level. It does not tell you the water is free of it.
PFAS is a large family of compounds, and each one can carry its own limit and its own detection behavior. A single clean line can therefore cover a lot of ground while proving much less than it appears to.
Find the Right Pages
Public water systems in the United States must issue an annual water quality report, often called a Consumer Confidence Report, under federal drinking water rules. Start with the table of detected contaminants. Check whether PFAS appears there at all, which units are used, what year the samples were taken, and whether each entry shows a number or a symbol such as ND.
If PFAS is missing from the table entirely, that is a question in itself. Ask whether the utility tested for it that year, and whether it tested at all.
Questions to Ask the Utility
A short call or email to the water department will often clear up more than the report does. Ask which PFAS compounds were tested and what reporting limit the lab used for each. Ask how many samples were collected, and from which points in the system, such as the treatment plant, the distribution lines, or your neighborhood.
Ask when PFAS was last sampled, whether more sampling is scheduled, and whether any result has been revised. A good utility will answer these questions plainly, and the answers tell you how much weight the clean line can carry.
Keep a Record Year to Year
Save each annual report in the same folder. When the next one arrives, compare the same contaminants, the same units, and the same sampling sources. A line that changes from ND to a number is worth a phone call, even if the number is small. A line that stays blank for years tells you little until you know the reporting limit behind it.
If You Run a Private Well
Utility reports do not apply to a private well. No one is sampling your tap on a schedule, so the responsibility for testing sits with you. Choose an accredited lab, ask for the reporting limit on each PFAS compound, and retest after any change to the well, the plumbing, or nearby land use.
What to Do With a Blank Result
Keep the report, write down the date, and treat the blank as a starting point rather than a final answer. If you want certainty for your own tap, a home test through an accredited lab gives you a number you can compare over time. Make sure the report lists the reporting limit for each PFAS compound, because that limit determines what a blank can tell you.
Once you know which compounds are present, treatment choices become clearer. Some homeowners compare reverse osmosis systems from providers such as Reverse Osmosis STL after they have a test in hand, but the result should guide the decision, not the other way around.
If you have a concern about exposure in your household, talk with your doctor, who can consider your family's situation directly.