PFAS monitoring of fish, water, and sediment

Since PFAS testing began in Minnesota’s lakes and streams in 2004, fish have been collected for PFAS from over 200 lakes and rivers, many of which have led to fish consumption advisories based on PFOS. It appears that PFAS contamination in fish is pervasive across Minnesota.

The need to monitor for PFAS continues and is expanding. With an increased awareness of the persistence and toxicity of some PFAS, concentrations of PFOS considered safe for fish and water consumption have dropped. Many of Minnesota’s lakes and streams potentially contaminated by PFAS have not been tested for PFAS in fish and those known to be contaminated need continued monitoring.

MPCA and others (including the Minnesota Department of Health and EPA) did significant fish tissue monitoring for PFOS from 2006 – 2013. Our existing data has shown PFOS has several characteristics that make it different from other bioaccumulative contaminants, such as mercury and PCBs:

  • Fillet concentrations do not correlate to age or length of fish, lipid (fat) concentrations, and trophic level
  • Wide variability of PFOS concentrations within fish species, as well as among species
  • The apparent lifetime of PFOS in fish is much shorter than the lifetime of mercury or PCBs

By 2018, the data was aging and we had very limited fish tissue data that was less than five years old. MPCA determined the need to retest previously tested waters and test new waters.

In 2018, paired water and fish samples were collected in 70 waters statewide (a mix of previously tested waters and untested metro waters) and evaluated for 13 PFAS chemicals. Low levels of PFOS in fish were found across the state indicating other potential sources of PFAS and the need for more monitoring. Based on those results, there are more than 60 waters that should be retested. The MPCA intends to continue sampling previously tested waters, and to do some testing of new waters. In 2020-2021, MPCA will sample fish tissue, water, and sediment at 20 total sites – 15 previously tested sites that showed higher levels of PFOS and five previously untested sites. Analysis will include 33 PFAS compounds and lower reporting limits than previous.

The Interagency Fish Contaminant Monitoring Program has proposed continued monitoring of fish, water, and sediment, and to do studies to increase the understanding of PFAS bioaccumulation in fish and the ecological risk of PFAS to other aquatic life, mammals and birds that eat those fish. However, there is no ongoing funding for fish tissue sampling and a source of funding for a bioaccumulation study has not been secured.

Following Safe-Eating Guidelines from MDH can help you lower exposure to PFOS and other contaminants when eating fish caught in Minnesota.