PFAS Testing Best Practices

About the author:

Marianne Metzger is laboratory sales executive for ResinTech Inc. Metzger can be reached at [email protected].

First let us define what PFAS is. 

What is PFAS? 

PFAS is any per-and polyfluoroalkyl substance, which are man-made organofluorine chemical compounds that have multiple fluorine atoms that are attached to an alkyl chain. These compounds are commonly called eight, six or four chains, which refer to the number of alkyl groups in the chain. Older compounds such PFOA and PFOS are eight chains while newer compounds, such as GenX, are six chains, with the thought being that less chains would make the chemicals less dangerous. These chemicals are not new. In fact, PFOA, a chemical previously used in the manufacturing of Teflon, was being produced by 3M in the 1940s. While these chemicals have been in use for many years, their numbers have grown as it is estimated there are more than 6,000 of these compounds with approximately 600 of them actively used today. 

These compounds are known for their resistance to water and oil, thus making them attractive to use in materials for waterproofing and stain resistance. They are frequently in products used every day from dental floss and other personal hygiene products to the clothes we wear and even in the food we eat from cookware to food packaging. In the 1970s, it was first discovered that these chemicals were being found in the blood of workers and then in the 1990s, it was found to be in the blood of the general population. There have been countless studies around PFAS and potential health effects, with some findings indicating an increased risk for kidney and testicular cancers, increase in cholesterol levels, decreased response to antibodies in vaccines, increase in high blood pressure in pregnant women, as well as low birth weights. 

As health effects were attributed to the presence of PFAS, they became known as emerging contaminants. In 2000, 3M began phasing out legacy chemicals, including PFOA, PFOS and PFHxS. The EPA formed a stewardship program in 2006 to encourage other manufacturers to eliminate PFOA and other similar eight chain compounds. While companies were phasing out the eight-chain compounds, they were busy introducing six-chain and four-chain alternatives with the most recognizable being Gen X. 

In 2016, EPA included six PFAS compounds in the third Unregulated Contaminant Monitoring Rule (UCMR), to determine how frequently and at what levels these compounds are found in our drinking water. The UCMR helps EPA determine if contaminants found in drinking water are at levels which may present a health risk. EPA uses information from the UCMR to determine if contaminants should be regulated under the Safe Drinking Water Act. According to results from the UCMR3, at least one PFAS contaminant was found in 610 water supplies in 48 states. 

To Regulate or Not?

Armed with information that these chemicals are prevalent in our drinking water and more studies questioning the safety of such chemicals, EPA issued a Lifetime Advisory Level of 70 ng/L (parts per trillion) either individually or combined for PFOA and PFOS. There are numerous questions about this group of contaminants as some of the shorter chains that were introduced more recently are proving more difficult to remove from drinking water and may have longer half-lives than the older eight chain compounds. There are various sites across the U.S. struggling with PFAS contamination in their drinking water supply. With no real direction from the EPA, many states have begun setting their own standards and Maximum Contaminant Levels (MCL) to help protect residents. This presents problems for states like Arizona, North Carolina, Missouri, Indiana and Oklahoma, which have regulations that prevent them from setting a standard that is lower than an EPA level, so they are awaiting direction from the EPA in order to establish a drinking water standard. EPA is hoping to gather additional information about PFAS contaminants by including them in the next UCMR5, which will look for other PFAS compounds and at lower detection levels.

Testing Methods

With all the action surrounding these contaminants, testing for them is becoming necessary to determine how prevalent they are and at what levels. There are a couple of methods and variations of these methods that are employed to detect PFC’s. EPA used method 537 in the UCMR3 and have since refined the method to offer lower detection levels. This method, or variations of this method, is used most often when testing for PFCs in drinking water. In 2019, the EPA validated Method 533 which allows for detection of more PFC compounds. It is being proposed that the next UCMR, which would be the fifth, will utilize method 533 to look for additional PFC compounds. There are some other methods for different matrices, but Methods 537 and 533 are intended for analyzing drinking water samples and are the most used methods, although they may be slightly modified.

Field Reagent Blanks

Field reagent blanks (FRB) are quality control samples intended to determine if the sample is positive and that it was not somehow contaminated during the sampling process. Accordingly, this is especially important with PFAS as they are prevalent in our environment. For a field reagent blank, the lab will provide an additional sample bottle along with a bottle of reagent grade water, pre-preserved and free of contamination. When you are in the field, you will use the bottle of reagent grade water and pour into the extra sample bottle, exposing the water to any possible contaminants in the sampling area. If sampling to meet regulatory requirements, a FRB may be required. Depending on how many samples are being collected, more than one FRB may be needed. For samples that are strictly for informational purposes, FRB may be skipped in an effort to reduce the cost of analysis. Sometimes the FRB can be collected and only analyzed if there is a detection in the actual sample. 

Preparing to Sample

Collecting samples for PFAS analysis requires some pre-planning. First, if you are shipping samples to a lab, check with the shipping company you plan to use to ensure you can ship samples overnight to the lab the same day you are collecting samples. Confirm the cutoff times for overnight deliveries to ensure you do not miss it. Usually, this means no collecting samples Friday through Sunday. However, it is not a bad idea to check with your lab to ensure there are no problems delivering your samples on the day you choose. 

Samples need to arrive at the lab at 10 degrees Celsius. Therefore, you will need to chill samples prior to shipping. Blue ice is not recommended and should be avoided, as it may contain PFAS compounds. If possible, locate a source of PFAS-free ice to use with the samples. If you cannot confirm that the ice you have available to you is PFAS-free, extra precautions will need to be taken. Standard practice to reduce cross contamination include double bagging samples and using ziplock bags when adding ice. Additionally, there is a long list of things to avoid when collecting PFAS samples and a variety of better options.

There are several reasons to test for PFAS, such as regulatory or health concerns, so it is important to properly sample to obtain the most accurate results. As you can see, there are multiple things to consider and plan for when sampling for PFAS, as it is not just as simple as filling up a bottle with water. It is a good idea to review sampling instructions from the laboratory, so you can plan appropriately. Considering that PFAS testing is rather expensive, the room for error is small and mistakes can be costly. If you have questions, call the laboratory you are using as they can help direct you. If you do not feel comfortable collecting your own samples, you can always look for an experienced sample collector.