The Bare Essentials of PFAS Sampling
What You Need to Know and Plan for Before You Collect a Drop of Water
By Nick Granata, LEP
Contributions By Jeff Arps, LSP
Per- and polyfluoroalkyl substances (PFAS) are a group of man-made chemicals that includes PFOA, PFOS, GenX, and many other chemicals. PFAS have been manufactured and used in a variety of industries around the globe, including in the United States since the 1940s. PFAS are known for their chemical stability, heat resistance, and oil- and water-repellence, which are attributed to their unique chemical composition. These qualities make PFAS useful in thousands of industrial processes and everyday consumer products. The persistence and mobility of some PFAS compounds, the disposal wastes (both manufacturing and end-use) combined with decades of widespread use in industrial processes, certain types of firefighting foams, and consumer products, have resulted in their presence at trace levels in most environmental media across the globe. In some respects, PFAS compounds are ubiquitous in the environment and in the blood of humans and other animals.
Current analytical methods for aqueous matrices can detect PFAS in the parts per trillion (ppt) range. To put that into perspective at a larger scale, one ppt is equivalent to a single drop of water in 20 Olympic-sized swimming pools. Unlike other chemical compounds, regulatory criteria for PFAS in drinking water are some of the lowest ever established. In 2016, USEPA set a drinking water advisory limit of 70 ppt for the sum of two PFAS compounds PFOS and PFOA. Since then, many states have issued guidance documents and/or promulgated even lower regulatory and health advisory standards, most as a sum of five or six compounds (including PFOS and PFOA) or on individual compounds, to address PFAS in drinking water.
The presence of PFAS compound in the environment has been the subject of increasing regulatory attention in recent years as emerging contaminants of concern. As a result, sampling and analysis of PFAS in groundwater, drinking water, and other matrices has steadily increased. Sampling conducted to determine the presence/absence or concentrations of PFAS in water is generally similar to other chemical compounds GSMSMS quadrupole techniques; however, additional considerations and protocols are necessary. Due to the ubiquitous nature of PFAS, its potential presence in common equipment, clothing, and sampling supplies, and the analytical sensitivity of results reported at ppt levels, there is a lot to consider before embarking on a PFAS sampling and analysis program.
Now it’s time to plan and get prepared -PFAS sampling and analysis requires a careful and cautious approach to ensure that the sampling efforts result in meaningful, accurate data so important decisions (such as the need for drinking water treatment or site remediation) can be made. Unlike other chemical analyses, PFAS are more susceptible to sampling contamination, which therefore requires sampling ‘blanks’ for proper QA/QC. Sample blanks can have a major impact on project costs since PFAS analyses cost two to three times more than analyses for more typical compounds.
Failure to plan properly and sample correctly may result in costly mistakes and erroneous data. Below are some of the bare essentials of PFAS sampling and what you need to know before you collect your first water sample.
Stakeholder coordination upfront is of utmost importance to ensure PFAS sampling objectives are well defined. Coordination between water company owners and operators, the laboratory, and possibly regulators should be conducted when developing PFAS sampling plans. Water companies should understand why they are sampling and what the potential outcomes may be, should PFAS compounds be detected. Communication with the laboratory, the water company, and regulators is important largely because the current state of PFAS knowledge and guidance from state and federal agencies are constantly evolving. As such, guidance on sampling protocols, analytical methods, communication of results, etc., are routinely being updated.
PFAS SAMPLE PLANNING
When developing plans for PFAS sampling, several critical items should be considered in advance. Coordination is necessary to determine if PFAS compounds may be present at the subject site and/or specific sample locations that may affect samples being collected (i.e. historical firefighting activity or current/historical septic systems). Additional discussions with the laboratory may be warranted based on the type of sample being collected. For instance, if collecting finished drinking water samples, PFAS-free sample containers provided by the laboratory will contain Trizma, which is added for buffering and free chlorine removal. If samples are not drinking water, preservatives will likely not be required. As noted, it is best to consult with your laboratory in advance of the sample collection to reconcile these
Individuals responsible for sample collection should adhere to Standard Operating Procedures for PFAS sampling. Some considerations prior to sampling include sample collection sequencing, equipment and supply requirements, decontamination vs disposable equipment, QA/QC protocols, etc. In addition, household and consumer products that are known to contain PFAS compounds, such as skincare products, insect repellents, and certain clothing, need to be strictly avoided when sampling by the individuals conducting the sampling. In the early days of PFAS sampling, scientists joked that all clothing should be avoided, creating a truly ‘bare essentials’ scenario!
EQUIPMENT AND SUPPLIES
Similarly, the use of certain types of equipment and sampling supplies may inadvertently cause cross-contamination and lead to compromised data. Whether sampling groundwater for a site investigation or collecting finished drinking water samples, careful attention is required to ensure equipment, supplies, system components, etc. do not contain PFAS compounds. For instance, the use of Teflon or other fluoropolymer-containing materials (Teflon-lined tubing or Teflon seals on sample bottles), should not be used, but HPDE materials are acceptable. Water repellant clothing and Write in the Rain field books are also potentially PFAS containing. Standard Operating Procedures for PFAS sampling should clearly spell out the various dos and don’ts, as well as acceptable vs. prohibited items.
When sampling for PFAS, the reuse of equipment between sample locations should be minimized or, if possible, eliminated. The same special considerations apply when using decontamination products to ensure products are PFAS-free and will not inadvertently cause cross-contamination of samples. In addition, only PFAS free water provided by a certified laboratory should be used for equipment decontamination.
QUALITY ASSURANCE AND QUALITY CONTROL
One of the most important aspects of designing a PFAS sampling program is to have good QA/QC protocols to ensure quality objectives are met so the data is valid and not subject to cross-contamination or other anomalies (again, we’re talking about parts per trillion!).
QA/QC samples including but necessarily limited to, including trip blanks, field blanks, equipment rinseate blanks, and duplicate samples, should all be built into your program. These quality control steps do add significant cost to the sampling budget; therefore accurate sampling can avoid the even greater costs of performing potentially unnecessary response actions.
PFAS sampling requires a well planned and thoughtful approach. There is simply a lot to consider!
Proper coordination and planning upfront can help avoid sampling pitfalls and the collection of erroneous data as well as minimize costs associated with resampling.