An Overview of PFAS Contamination in Seafood

Posted on Behalf of  Kathy Chan, Amanda Buerger, Kathleen Chen

The United States (U.S.) Food & Drug Administration (FDA) established the Total Diet Study (TDS) program to regularly monitor nutrients and contaminants in the U.S. food supply (FDA, 2021a). TDS samples include commonly consumed foods, such as breads, cakes, fruits, dairy, vegetables, meats, poultry, fish, and bottled water (FDA, 2021a). In instances in which foods contain detectable levels of possible contaminants, the FDA conducts safety assessments to evaluate whether levels constitute a human health concern (FDA, 2021b). One group of contaminants of interest are per- and polyfluoroalkyl substances (PFAS), which are synthetic chemicals used in many products (FDA, 2021c). Since 2019, the FDA has analyzed 440 TDS samples over four collection periods (one national and three regional) for 16 select PFAS (FDA, 2021d). The concentrations of PFAS in food are used to calculate an estimated internal dose based on likely human consumption patterns, and then the estimated dose is compared to toxicological reference values from various agencies, including reference doses from the Environmental Protection Agency developed by the Agency for Toxic Substances and Disease Registry (ATSDR) (EPA, 2017; ATSDR, 2021). In June, 2021, the FDA announced that it intends to conduct a targeted survey of PFAS in the most commonly consumed seafood in the U.S., based on results summarized below (FDA, 2021b). The FDA has concluded that there is no indication of a human health concern from PFAS in the U.S. food supply from these results; however, because of the limited sample size of these studies, the FDA noted that the results are not necessarily representative of the entire U.S. food supply (FDA, 2021d; FDA, 2021e). Additionally, the FDA has indicated that efforts to monitor contaminants in the U.S. food supply are ongoing.

Across four iterations of PFAS surveys, very few foods had detectable PFAS levels. Of the 440 samples analyzed, PFAS were identified in seven food samples, including five samples of processed seafood, as detailed below (FDA, 2021e). Similar results appear in both national and regional PFAs surveys. Regional samples were collected from three different cities in one of six regions in the U.S., and are more likely to vary by location or time of year (FDA, 2021a; FDA, 2021e).  The PFAS detected in these surveys included perfluorooctane sulfonate (PFOS), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA).

  • In August, 2021, the FDA released results from its first PFAS survey in nationally distributed processed foods and found that 164 of the 167 samples did not contain any detectable PFAS (FDA, 2021d). Of the three samples with detectable PFAS, two were seafood samples: one sample of fish sticks or patties, described as “frozen” and “oven-cooked,” contained detectable PFOS (33 parts per trillion [ppt]) and PFNA (50 ppt), and one sample of canned tuna “in water” that was “drained” contained detectable PFOS (76 ppt) and PFDA (72 ppt) (FDA, 2021f).
  • According to a June, 2021 update, 93 of 94 regional samples did not contain any detectable PFAS (FDA, 2021b). One baked cod sample had detectable PFOS (98 ppt) and PFNA (233 ppt) (FDA, 2021g).
  • According to an October, 2020 update, 89 of 91 regional samples did not contain any detectable PFAS. One of the two samples with detectable PFAS was a seafood sample: one sample of tilapia described as “[r]aw...[f]resh, [f]rozen [and in its n]atural [s]tate,” had detectable levels of PFOS (87 ppt) (FDA, 2020a).
  • In a second update from October, 2020, 87 of 88 regional samples did not contain any detectable PFAS. One tilapia sample had detectable PFOS levels (83 ppt) (FDA, 2020b).
  • Notably, several seafood samples across the four surveys conducted did not have detectable PFAS levels, including frozen fresh cod, baked tilapia, pre-cooked shrimp with shells removed and no tails, boiled shrimp, baked steaks/fillets of salmon, and pan-cooked catfish with oil (FDA, 2020a; FDA, 2020b; FDA, 2021f; FDA, 2021g).

The detection of PFAS in fish samples is not unexpected given the high mobility and environmental ubiquity of some PFAS and the demonstrated transfer of PFAS in the aquatic environment.  Other market basket surveys have reported low but detectable concentrations of some PFAS in commonly consumed fish and shellfish caught in the U.S., with higher concentrations found in fish caught in the Great Lakes, which are known to be contaminated with PFAS (Ruffle et al. 2020). Notably, TDS does not intentionally include samples from areas with known PFAS contamination (e.g., the Great Lakes and other areas of water contamination), which could have different uptake patterns and PFAS concentrations, as noted in the other surveys (FDA, 2021b).

FDA’s targeted survey will include 80 retail seafood samples, including shrimp, salmon, canned tuna, tilapia, pollock, cod, crab, and clam (FDA, 2021b).  Additional surveys are needed that include a larger sample size, particularly for seafood, and additional methods to examine specific PFAs sources in different foods (e.g., from PFAS-containing packing materials, processing equipment, or PFAS-contaminated soil or water) in order to better characterize dietary PFAS exposure and potential risk in the U.S. population. Finally, although the FDA has concluded that there is no human health concern from PFAS in the U.S. food supply, using detection methods for PFAS with lower limits of detection and quantification would assist with better tracing of the source of PFAS in foods.  

Cardno ChemRisk scientists have decades of experience understanding hazard and exposure associated with perfluoroalkyl substances, or PFAS, and potential risks related to foods. Please visit Cardno ChemRisk’s PFAS and Food and Beverage pages for more information regarding our capabilities. If you would like to learn more about our capabilities, or have any further questions regarding these topics, please contact Heather Lynch or Neva Jacobs.