Destroying toxic chemicals with pluff mud bacteria- a moment of science

Storm Team 2

“I could find you PCB on almost any piece of soil on the planet- from the Arctic to the Antarctic.”

Polychlorinated biphenyls, or PCBs were widely used from transformers to insulators. They were even sprayed on dirt roads to keep the dust down from the 1920s until the late 70s when they were banned for their toxicity. According to NOAA, nearly 1.5 billion pounds of PCBs were produced during this time frame.

Low concentrations are generally not a human health problem but hot spots of potentially hazardous concentrations of PCBs still exist today as these man made chemicals settle down into the sediment. Hal May, microbiology professor at MUSC, explains:

“We did a really good job of creating a very resilient compounds. There’s 209 of them. They don’t break down readily and they’re everywhere still. And this has been the big problem. But just getting rid of them out of a marsh or something like that isn’t straightforward.”

The current method of clearing out especially problematic areas like the Hudson River is by digging up the contaminated soil and moving it to a toxic waste zone.

“That’s not a cheap way to fix the problem. So that’s been our motivation to find a more passive way to treat a site and to do something about the PCBs and keep it out of the food chain”

To do that- May started by digging in the mud.

A sample he gathered in the pluff mud on the Ashley River over 20 years ago proved to be a diamond in the mud as it contained a microbe that could help get rid of those harmful PCBs. 

A Plan of Attack

There needs to be a plan of attack to destroy this stable compound. First things first- knowing what your target looks like.

“It’s a biphenyl ring. So think of two hexagons with a bond in between the two of them. At each one of those points around the hexagons is a place where a chlorine can be substituted on,” May said.

One. Attract and hold onto the harmful compound. This is done by a system called SediMite. 

Two. Clear those chlorines from the ring. The bacteria May found in the pluff mud was perfect for this as it was an anaerobe- meaning it doesn’t require oxygen and as such can break the first line of defense that PCB has. This allows the third and final step to come in: another bacteria that requires oxygen finishes the job by breaking the rings apart- destroying the PCB. 

This three pronged attack is being tested to degrade PCB in afflicted areas as if left untreated, high concentrations of this harmful chemical can potentially cause human health concerns as it moves up the food chain through eating fish that contain toxic levels of the chemical.

Storm Team 2 Meteorologist David Dickson

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