Dioxin at record levels

Tuesday, January 11, 2007

MIDLAND -- Dow Chemical Co. and the state Department of Environmental Quality are forming a plan to tackle the highest levels of soil contamination found in a region surrounding a chemical plant that the DEQ has ever recorded.

Dow Chemical Co.-hired Ann Arbor Technical Services workers were finishing a study of a six-mile stretch of the Tittabawassee River between the Tridge and the Smith's Crossing bridge in Midland when three samples showed heavy concentrations of dioxins and furans.

John C. Musser, Dow spokesman, said the depths where the samples were found indicate contamination that may have occurred nearly a century ago.

The contractor measured the toxins at 87,000 parts per trillion, 84,000 parts per trillion and 69,000 parts per trillion, all on Dow property. Nearby samples measured between 100 and 1,000 parts per trillion.

By contrast, Michigan's residential contact limit for dioxin in soil is 90 parts per trillion. The state average is 7 parts per trillion.

The previous most-contaminated sample taken near a chemical plant was 2,000 parts per trillion in the Upper Peninsula, said DEQ spokesman Robert McCann. That contamination also contained dioxins and furans.

"We were expecting we might find some high numbers," McCann said. "I wouldn't say we are shocked, but we are concerned."

McCann hopes to begin cleanup by the end of the month. The job might last until the summer depending on weather, the walleye spawning season and other factors, McCann said.

The sampling -- which began in August -- involved extracting soil with small cylindrical tubes at various depths. Now crews will use the same tools to take samples within feet of the original sites to determine the size of the contaminated regions.

"We want to find out if it's the size of a bread basket or a bus," Musser said. "Then we want to take action as quickly as possible and as safely as possible."

Crews could dredge the contaminated sites or use other methods to assure the river can't carry the contaminated soil downstream, Musser said.

The 87,000 parts per trillion sample came from a spot slightly more than a mile south of Smith's Crossing, in soil 6 inches to one foot beneath the riverbed.

Workers took the 84,000 parts per trillion sample in a riverbank near the middle of the six-mile study area. Workers discovered the contamination between a half-foot and 4 feet underground.

The 69,000 parts per trillion sample was from the riverbed next to the Dow plant, near a pipe that once carried contaminants from the site into the river.

Six other samples taken near the pipe registered between 10,000 and 50,000 parts per trillion of dioxins and furans.

So far, no other sample has measured above 10,000 parts per trillion.

Ann Arbor Technical Services is done taking samples and continues to analyze the findings. Musser said the final report is due Thursday, Feb. 1.

The initiative, dubbed GeoMorph, is designed to look at the Tittabawassee River's behavior.

The company ultimately will analyze the entire 22-mile stretch of the Tittabawassee River and the first six miles of the Saginaw River. Researchers are mapping the river's landscape, analyzing potential changes in water flow because of manmade and natural obstacles, and taking samples.

The project is part of Dow's work plans for cleaning dioxin along the Tittabawassee River. The DEQ requires the company to measure the scope of contamination downstream.

Musser said all of the contaminated spots match the "fingerprints" of previously discovered toxic samples collected in the area.

The samples' makeup contains 92 percent furans and 8 percent dioxins. Two percent of the dioxins are TCDDs, which some scientists call the most toxic form of the carcinogen.

Dioxin is linked to some forms of cancer, reproductive problems and weakened immune systems in laboratory animals. However, the World Health Organization says dioxins are not considered as toxic as once thought. Furans are in the same family of carcinogens as dioxins, McCann said.

"Dilution was the solution," Musser said of Dow's pre-World War I practice of releasing contaminants into the river during high-volume water flows.

Dow has changed its disposal practices since then, Musser said.

Officials at the Midland plant have contracted other studies. Also in progress is the study of surface soil on 350 Midland residents' properties.

Objectives include:

  • Determining the local distribution of soil characteristics that might influence bioavailability -- the ability of substances to absorb into the body -- of dioxins and furans.
  • Developing information about the distribution of contamination of Midland surface soil.
  • Determining whether additional Dow-related hazardous substances are present in Midland soil.
  • Maintaining anonymity of property owners.

Contractors from CH2 MHill of Englewood, Colo., finished the study in December and are analyzing the data.

In August, University of Michigan researchers finished an exposure study to find the most important factors in determining dioxin levels in people. Researchers determined that age was the largest contributor. v

Justin Engel is a staff writer. You may reach him at 776-9691.

2007 Saginaw News


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