They Call them Emerging Contaminants for a Reason – July 2019

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They Call them Emerging Contaminants for a Reason – July 2019

By: Steve Williamson, CPG

Because of situations like ‘Flint Michigan’ states are reacting much faster than the U.S. EPA on the establishment of maximum contaminant levels (MCLs) for PFAS compounds and are establishing their own safe drinking water limits. As a result, there are a multitude of PFAS drinking water limits across the nation, ranging from 660 nanograms per liter (ng/L) in Nevada to 10 ng/L in New York. The ubiquitous nature of PFAS compounds and the establishment of such low drinking water limits requires the use of strict sampling and handling procedures to minimize cross contamination in the field and laboratory.

Recently, Cox-Colvin completed a study using our onsite monitor well to evaluate the influence of different sampling procedures and equipment for the collection of PFAS groundwater samples. To minimize the study variables, all the samples were submitted to the same laboratory for analysis using their “modified” method 537[1]. Two compounds, perfluorobutanoic acid (PFBA) and perfluorohexanesulfonic acid (PFHxS), were reported at trace concentrations in all the groundwater, field quality assurance and quality control (QA/QC), and laboratory QA/QC samples. Because the compounds were present at similar concentrations in the laboratory method blanks, it appears the source of PFBA and PFHxS contamination in this case is laboratory-related rather than groundwater- or field-method-related. Laboratory cross contamination by some compounds is to some degree common at the part-per-trillion reporting limits required for PFAS analyses.

The low drinking water limits combined with the absence of EPA accredited analytical methods, makes the sampling and analysis of environmental samples for PFAS extremely challenging.  Although proper sample collection and handling procedures are important, strict laboratory QA/QC procedures are absolutely necessary to prevent reporting of false positives. Until the EPA develops standardized methods for PFAS analysis, rigorous laboratory QA/QC protocols (i.e., use of appropriate laboratory QC samples) are key to the successful analysis and interpretation of PFAS analytical results. In addition, reporting to the practical quantitation limit (PQL) instead of the method detection limit (MDL) may be a good way to limit false positives. Lastly, performing detailed data validation is highly recommended as a way to ensure the quality of the data.

Published in the July 2019 Cox-Colvin & Associates Newsletter: Focus on the Environment

[1] Currently, there is not a US EPA accredited laboratory method for PFAS analysis of non-drinking water and/or solids (i.e. soil & sediment). Consequently, laboratories have had to develop their own “modified” methods based on US EPA approved Method 537.1.  In June 2019, EPA posted draft validated SW-846 Method 8327 (non-potable water matrices) for a 30-day public comment period. 

Steve Williamson is a Senior Scientist with Cox-Colvin & Associates, Inc. He holds a BS degree in Environmental Health and an MS degree in Hydrogeology from Wright State University. Mr. Williamson has over 30 years' experience working on brownfields, solid and hazardous waste, and groundwater contamination projects in Ohio and the Midwest.