A PFAS result is rarely one clean number. Most reports list each compound with a value, and somewhere on the page sits a line for the reporting limit, often paired with a label such as "not detected" or "ND." It is easy to skim past that line. Don't. It tells you the smallest amount the lab could measure with confidence, on that day, using that method.
A recent piece from Circle of Blue's report on PFAS in drinking water lands right on that line. Published October 23, 2026, and originally carried by Inside Climate News, the article was written by Alissa de Chassey. Its headline argues that PFAS contamination "may be underestimated," and its summary turns to the limit itself: when PFAS concentrations in drinking water "fall below laboratory reporting limits," the result needs careful reading. That is the detail worth carrying into your own report.
Not detected does not mean none
When a report says "not detected," the accurate translation is "below what this method could see on this sample." It does not mean the water is free of the compound. Think of it as a sensitivity rating for one test on one day, not a verdict on your tap. A lab's floor is a practical tool, shaped by instrument sensitivity, sample handling, and the analytical method. A reading under that floor can still reflect something real. Homeowners tend to hear zero and stop asking questions, and that habit is exactly where a useful test becomes a false comfort.
Four things to check on your report
Pull out the paperwork before you decide anything. First, find the reporting limit for each compound you care about, and compare it with the value printed beside it. Second, read the result label closely. "Not detected," "below reporting limit," and a measured number are three different entries, and they should not be treated as one. Third, check which compounds were on the panel. Not every PFAS test looks for the same list, so a clean result may only cover the chemicals the lab was asked to find. Fourth, confirm the sample date and the report date, since they can differ.
When a zero still needs a question
If your report reads zero but the limit is higher than you expected, treat it as an open question, not a final answer. Ask the lab, in writing, what the limit is for your sample and what it means for the compounds you care about. Keep that written answer with the original report so the two travel together. Then take the report to your utility or your local health department, who can explain how the result fits with other data for your area. If your household includes someone with particular health concerns, bring that to your doctor, who can speak to your specific situation. A water report cannot answer that question for you.
If you are choosing a filter
A result with a high limit changes the filter conversation too. You need a baseline before you can judge whether a unit is doing its job, and a number you cannot trust is a weak baseline. Ask the installer what the unit is rated to reduce, and whether that matches the compounds on your report. Read the certification on the unit rather than the box front, and keep a copy of your report with the filter paperwork. If you want a second set of numbers from a source outside your utility, Jones Air & Water offer free in-home water tests, and you can compare what you get against your own report line by line.