THE CHALLENGE OF ‘NON-DETECTS’ – INTERPRETING AND VALIDATING LOW-LEVEL PFAS DATA

Understanding what a “Non-Detect” Means

At the 2026 Battelle Chlorinated Conference, ddms Senior Environmental Chemist Virginia Clauser took on a frequently asked question: what does a “non-detect” tell you?

Labs can measure PFAS at smaller and smaller concentrations every year, which sounds like good news until you remember that “didn’t detect” and “it isn’t there” aren’t the same thing. Detection limits, background contamination, and how a lab chooses to report results all shape what shows up (or doesn’t) on your final report.

As you can tell on the poster below, non-detect doesn’t mean zero. It means “not above this threshold, under these conditions.” That’s a meaningful difference when regulators, risk assessors, and your own team are making decisions based on that number.

The fix isn’t complicated, but it does take discipline, solid QA/QC, and a careful second look at the data before anyone draws a conclusion from it.

With PFAS, what you don’t see can matter just as much as what you do — as long as you know how to read it