Star Tribune: 3M contaminant study finds mixed results

In 2008, the South metro portion of the Mississippi River was declared as impaired for excess PFOS in fish tissue. PFOS, a compound produced by 3M until 2002, had contaminated groundwater in the east metro area and also made its way into the Mississippi River.

A recent Star Tribune article highlights the findings of newly completed research on the progress of clean-up efforts. The research was conducted in 2012, and included water, fish tissue, sediment, and macroinvertebrate samples. What did we learn?

For fish, the 2012 results indicate lower overall PFOS concentrations in Pool 2 fish (except carp). However, significantly higher concentrations remain in carp and freshwater drum taken from the lowest section of the river near the 3M plant.

For water samples, PFOS levels downstream of the 3M plant were significantly higher than in the rest of Pool 2.

Sediment samples showed that the highest concentrations of PFOS were found immediately downstream of the 3M plant discharge area, with slightly elevated levels downstream of the MCES Metro Plant and the Marathon Ashland refinery in St. Paul Park. This is the first such study of sediment in Pool 2, so there is no previous study for comparison.

The highest PFOS concentrations in macroinvertebrates were found downstream of the 3M plant discharge, with slightly elevated levels found at a few places upstream. This was the first such study of the aquatic insects that are an important part of the food chain in Pool 2, and thus there is no prior study for comparison.

FMR is pleased that progress has been made in reducing overall levels of PFOS throughout Pool 2. However, these results indicate the need for ongoing restoration and remediation, especially in the southern portion of the metro Mississippi River.