Saturday, January 9, 2016

PCBs: The Nature of the Beast

Image result for skull and crossbones image(first in a series)

Polychlorinated biphenyls (PCBs) are an assortment of man-made chemical compounds that were commonly used as coolants and electric insulators. Oils containing PCBs were carelessly discarded for decades. They are found all over the place in southeast Michigan, contaminating many of our waters. Even low levels of PCBs can have acute, chronic health consequences, including cancer. Consider these particulars from Wikipedia:

Because of PCBs' environmental toxicity and classification as a persistent organic pollutant, PCB production was banned by the United States Congress in 1979 …

The maximum allowable contaminant level in drinking water in the United States is set at zero, but because of water treatment technologies, a level of 0.5 parts per billion is the de facto level.

[PCBs] … are chemically fairly inert, being extremely resistant to oxidation, reduction, addition, elimination, and electrophilic substitution.

The resistance of PCBs to oxidation and reduction in the natural environment makes them very stable compounds, not decomposing readily. They have a long half life (8 to 15 years) and are insoluble in water, which contributes to their stability.[11] Their destruction by chemical, thermal, and biochemical processes is extremely difficult, and presents the risk of generating extremely toxic dibenzodioxins and dibenzofurans through partial oxidation. Intentional degradation as a treatment of unwanted PCBs generally requires high heat or catalysis

Like many lipiphilic toxins, PCBs biomagnify up the food chain. For instance, ducks can accumulate PCBs from eating fish and other aquatic life from contaminated rivers, and these can cause harm to human health or even death when eaten.

The U.S. Environmental Protection Agency (EPA) and the Michigan Department of Environmental Quality (MDEQ) have endeavored to remedy PCB contamination in Michigan for about 40 years with varying levels of success. This series will examine one such effort that has been botched badly.

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