PFOS levels in Mississippi are declining, but remain high below 3M plant

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For release: Jan. 28, 2013

Contact: Ralph Pribble, 651-757-2657

PFOS levels in Mississippi are declining, but remain high below 3M plant

St. Paul, Minn. -- Levels of a 3M chemical found in Mississippi River fish below the Twin Cities are declining but remain high between the 3M manufacturing plant in Cottage Grove and the dam at Hastings.

The Minnesota Pollution Control Agency (MPCA) reported these findings today after extensive sampling over the past year of the water and aquatic life from Pool 2, a 32-mile length of the Mississippi between the Ford Dam and Hastings, for perfluorooctane sulfate, or PFOS.

The MPCA has been sampling fish in the river as part of followup studies of the environmental impacts of perfluorinated chemicals (PFCs), a class of chemicals that do not break down in the environment and accumulate in animals and people. 3M began manufacturing the chemicals at the company’s Cottage Grove facility in the 1940s, disposing of wastes at several east metro area locations.

The chemicals have contaminated groundwater and fish in area lakes and the river. 3M announced a phase-out of PFOS and PFOA production in the early 2000s. The MPCA has listed this portion of the river impaired for PFOS since 2008.

The data show the overall average PFOS concentrations have declined in fish tissue taken from the entire 32-mile pool. However, the fish, water, sediment and insect samples taken from the lowest reach of the pool, downstream from the 3M Cottage Grove plant, continue to show significant contamination compared to the upper reaches.

MPCA Assistant Commissioner Rebecca Flood said the results are good news but show there’s still work to be done to protect the river and its aquatic ecosystems.

“It appears the 3M phase-out of PFOS manufacturing, and the MPCA-ordered cleanup of three 3M disposal sites and a landfill that received 3M wastes, are beginning to reduce levels of PFOS in the river and its food chain,” Flood said. “But the levels around and downstream of the 3M Cottage Grove facility remain significantly higher.”

The lower reach of the pool received PFOS-laden wastewater discharges and contaminated groundwater inflows for decades before the PFOS phase-out and installation of activated-carbon wastewater treatment at 3M’s Cottage Grove plant.

The monitoring just completed replicated a 2009 study, and was the first time the MPCA collected sediment and sediment-dwelling insects for PFC analysis. The MPCA collected 296 fish of five species, and 32 water samples from 12 locations on the river. Sediment samples were collected from 50 locations and insects were collected at 44 of the 50 sites.

The MPCA will use these new data and previous studies to review water quality guidelines designed to protect aquatic life and human health for Pool 2, and to determine whether any change in the impaired waters listing is warranted. Any changes to the impairment status would be proposed for public comment in fall 2013 as part of the federal Clean Water Act’s 2014 impaired waters list.

Broadcast version:

Levels of a 3-M chemical found in fish in the Mississippi River are declining but are still high in parts of the river, according to the Minnesota Pollution Control Agency. Results from recent M-P-C-A sampling show levels of a chemical called “P-FOS” [pronounced: PEA-foss] are generally falling, but fish between 3-M’s Cottage Grove manufacturing plant and the Hastings dam still have higher levels.

The chemicals were manufactured at the Cottage Grove plant and were phased out by 3-M in the early 2000s.


The mission of the MPCA is to work with Minnesotans to protect, conserve and improve our environment and enhance our quality of life.

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