What’s in the River: Heavy metals

River Raisin running through Manchester along Union St.

This is the last article in a three-part series on what is in the River Raisin. Read the first two here and here.

by Claire Pajka

Industry along the River Raisin was good for stimulating the economy, though it didn’t have the same positive effect on the river itself. When the lower 2.6 miles of the River Raisin were designated as an Area of Concern in 1987, copper, zinc, and chromium were the heavy metals of highest concern.

The numerous industries and factories surrounding the Raisin are the most likely sources for the abundance of heavy metals in the water. Chromium was and is common in steel, chrome plating, dyes and pigments, and leather and wood preservation. Not only is chromium released through industrial practices, but through sewage and fertilizers as well. Newton Steel, a company along the Raisin, likely contributed to the heavy metals collecting in the riverbed. Copper – which is present in industrial processes as well as production of pipes, cables, and wires – and zinc were likely compounded by the numerous factories and landfills.

Though copper, zinc, and chromium are all required in small amounts for normal bodily function, large doses create adverse and toxic health effects. Similar to PCBs, heavy metals can settle into sediments and become buried at the bottom of streambeds where they can remain for long periods of time. Metals also pose a problem in that they are non-biodegradable, and the natural environment is unable to break them down into less harmful substances. This means that once a heavy metal enters a waterway, it will often remain there for a substantial period of time. Because they are unable to be broken down in the environment, they are collected and accumulated within the bodies of aquatic organisms living in that ecosystem, such as macroinvertebrates and fish. This is why consuming fish from regions polluted with heavy metals is dangerous: when the high levels of contaminants stored within the body of the fish are ingested, the pollutants are then stored and accumulated within the human body. Topical exposure can also happen through physical contact with contaminated sediment, such as when wading in polluted water.

Originally listed with PCBs as a primary co-contaminant of concern on the Beneficial Use Impairment sheet for the River Raisin Area of Concern (AOC), according to the current impairment list updated in August of this year, heavy metals are no longer a primary contaminant of concern in the AOC. However, levels that are still harmful to human health exist within fish, and those consuming fish from certain areas in the river should take care in both the amount and the type of fish that they consume. To learn more about safe fishing precautions and regulations for areas throughout the Raisin, see the article “Gone (Safely!) Fishing in the River Raisin”.

Main sources for this article:

EPA website: https://www.epa.gov/great-lakes-aocs/river-raisin-aoc#stlouisbuis

Great Lakes Restoration: https://www.glri.us/node/204

Updated River Raisin AOC BUI sheet provided by Barry LaRoy: https://drive.google.com/file/d/1k8Qu4yny6orKjQ9B3pSH2gqAfL_DzIgz/view?usp=sharing

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by Sara Swanson

Sara Swanson is an editor, writer and founder of the Manchester Mirror.