FAQ: PFAS Testing for Soils and Crop Tissues

How do PFAS get into Farms? 

There are two main ways for soil and planted crops to be exposed to PFAS. The first way is through on-site agricultural practices that may introduce PFAS directly to farms. These management activities can include

1.  irrigation with PFAS-contaminated water like treated wastewater effluent or contaminated groundwater (e.g., wells) and surface water sources (e.g., ponds, streams, and lakes), and 
2. land application of PFAS-contaminated biosolids or wastewater residuals.

PFAS may also be introduced to farm systems through factors that are beyond farm management activities, such as proximity to a potential point source. Potential point sources include industrial discharges from wastewater treatment plants or manufacturing sites, landfills, and areas where aqueous film-forming foam (AFFF) was utilized in the past (airports, military training bases, and fire training areas).

Some PFAS chemicals can accumulate in the soil profile, while others are transported to groundwater or surface water sources nearby. Planted crops and vegetation can absorb PFAS from the soil or the water within the soil. Because PFAS don’t degrade easily in the natural environment, they can persist in farm environments even long after potential PFAS sources are eliminated.

How PFAS move in the environment is influenced by a lot of factors, such as PFAS chemical properties, soil type, underlying geology, groundwater depth, flow direction, site-specific conditions, among many others. Proximity to PFAS sources alone does not mean your farm resources are contaminated. However, it may be worth considering testing if there is a confirmed PFAS issue on the farm or in the surrounding areas.

What Laboratories test for PFAS?

Since PFAS are emerging contaminants, only a handful of laboratories in Pennsylvania can test for them.  Please refer to the PFAS Testing Services and Laboratories Directory fact sheet for a full list of laboratories with soil and plant tissue testing capabilities. Laboratories may provide sampling kits containing bottles and instructions for collecting, handling, and shipping samples, specific to the US EPA Method 1633A or a modified version, depending on their capabilities.  Currently, PFAS testing can cost approximately $250 to $500 per sample, depending on the type of sample and method used.  Farmers may be eligible for federal support programs that offer financial assistance, such as the Conservation Evaluation and Monitoring Activity. For more information, contact your local USDA Service Center, which can be found online.

Where should I collect samples to test for PFAS?

Laboratories may provide you with specific guidance on where and how to collect your samples. However, in general, where you collect a sample depends on the nature of your sample and your testing goal. To evaluate PFAS levels in soil, priority can be given to fields that are likely impacted by a potential source, e.g., plots where biosolids were applied, irrigated with PFAS-contaminated water, etc., or sites with specific use, such as pasture for animal grazing or growing produce for human consumption.

If farm produce is of interest, then edible portions of fruit crops and vegetables can be sampled. If you are trying to assess PFAS levels in crops used for feeding livestock, sample the grains and stover (e.g., corn stalks and straw), hay and pasture grasses, and leafy material or soil where livestock graze. It may be necessary to sample more than one field or area to get a representative assessment of the farm.

How do I collect and store samples to avoid cross-contamination?

Collection guidance for soil and plant tissues is based on US EPA method 1633A. However, laboratories may modify their testing methodologies based on the type of sample. It is therefore important to follow the sampling instructions you receive from the laboratory and only collect your samples in the bottles or containers they provide. If samples are representative of a large area, laboratories may request you to take a duplicate sample. A duplicate sample is a second sample collected from the same sampling location (e.g., field or lot). It is used as a quality control measure on the accuracy of the sampling and laboratory analysis process. If the laboratory needs a duplicate sample, they will include extra sample supplies and instructions for sampling.

Here are some general sampling tips to avoid sample contamination:

• PFAS are common in many household and personal care products. Whenever possible, avoid the use of stain or water-resistant products during sampling.
• Wear nitrile gloves during sampling (avoid latex gloves).
• Use laboratory-provided sample bottles and containers
• Use stainless steel sampling equipment such as scoops and spoons for soil and knives or scissors for plant tissue.
• Do not rinse or wash plant tissue before sampling.
• Do not cut up or homogenize soil or plant tissue samples unless instructed to do so by your testing laboratory.
• Keep collected samples cold (≤ 6 ºC) by storing them in the fridge, freezer, or on ice. Ship them as soon as possible with sufficient ice to keep them cold. Most laboratories will request overnight shipping to prevent the ice from melting.

How do I interpret my test results?

There are no federal or state regulations for PFAS in soil, plant tissue, or animal products. As more research and monitoring studies are conducted, states may develop varying guidelines and recommendations. For general help interpreting your soil and crop tissue test results, refer to the PFAS Test Results – What Do the Numbers Mean fact sheet or reach out to Dr. Daniella Carrijo at daniela.carrijo@psu.edu or 814-863-2535.