The PCB Challenge

Throughout the 1800s, skies over European cities were dark with the smoke of burning coal. In Britain alone, dense populations, a shortage of wood, and new commerce derived from steam power “fueled” coal’s use from 50 million tons in 1850 to 250 million tons by 1900. For rich and poor, the sulfurous, large black chunks of soft coal were a staple commodity and primary source of heat, energy, and industry.

Along the way, methods improved for carbonizing coal—heating it at high temperatures in furnaces—to make coke. This refinement became the key to meeting increased demands for iron and steel production, and it provided a source of fuel for locomotives. With coal-gas-powered lighting and longer workdays, the Industrial Revolution flourished, and with the dubious benefits of longer workdays, life sped on toward a new century. Galvanized by coal, business was booming, new technologies arose, and metered gaslights lit parlors, brought theatres to life after dark, and brought safety to street corners.

Amidst these innovations, a byproduct called coal tar was created. This sticky, viscous stuff (resembling the creosote made from wood used on railway ties) turned out to be ideal for mixing with stones to create a sealed, waterproof surface called tarmac (tar over macadam). Scientists found that coal tar had medicinal properties, too, and discovered a chemical cornucopia of agents that could be derived from the product.

A Miracle in the Making
But one product, first synthesized by German scientists, came to be hailed as a miracle discovery. It was nonflammable, had tremendous insulating capacity, and could be used as a coating, an extender for paints, a flame retardant, and much more. It was inert, nonreactive, and nonconductive with a high flashpoint. This miracle product derived from coal tar was called polychlorinated biphenyl (PCB), and for decades its stable chemical properties were exploited for everything from carbonless paper to waterproofing. One of its biggest draws came during the electrification boom. Its stability and inert property made it perfect to insulate transformers and capacitors.

PCB sold in huge quantities around the world. Scientists continued to experiment and found the properties of the substance could be enhanced. With added carbon atoms and chlorine mass, PCB became a nearly waxy substance, ideal as an extender for pesticides to increase their adhesion when sprayed. And it lasts—resistant to processes of natural degradation—for a long time, cycling through air, water, and soil for decades.

Today, however, with the benefit of history, biomedical science, and technology on our side, all of this sounds like a recipe for environmental disaster. Which in effect it was. PCBs were the proverbial double-edged sword. They could reduce the risk of death from fire when added as a flame retardant to clothing and upholstery, keep capacitors and transformers cool, and stabilize paints, hydraulic fluids, and floor finishes. Yet it was these very desirable attributes that made them the lingering environmental health threat that today, more than four decades after they were banned from use, continue to plague us in with their resistance. And the US was the largest producer of PCBs.

“We didn’t always hate them,” says Kevin Sowers, Ph.D., associate director and professor at the Institute of Marine and Environmental Technology (IMET) at the University of Maryland in Baltimore. “They were called the ‘miracle chemical’ because of their stability and were perfect for cooling. PCBs used for cooling in high-temperature situations would not boil off, and because they had dielectric properties they could insulate but not conduct. They were safe to use and would not short out electrical elements, such as transformers and capacitors.

“But because they are this miracle,” he explains, “they aren’t going anywhere, and the manufactured product was so stable in its enhanced forms they are not going to break down from exposure to natural environmental processes. They need to have special enzymes to break down, but you need a way to get the enzymes to these chemicals.”

As an anaerobic microbiologist, Sowers has been involved in researching methods that would be the perfect “organic recipe” to render PCBs harmless, because as he explains, “this is a global problem and they are found everywhere, including such unlikely places as the Arctic.”

Early Warning Wake-Up Calls Largely Ignored
For decades, scientists and health professionals knew that the chemical exerted dangerous properties. More than 100 years ago, exposure to chlorine during manufacturing caused disfiguring acne on workers, and the condition was dubbed chloracne, yet it would be another half century until the link to aromatic hydrocarbons was identified.

As the beneficial uses of PCBs multiplied, manufacturing escalated, and users and manufacturers of PCBs often put the effluent from those processes into the sewer systems, most of which were directly linked to public waterways. By the 1930s, public health experts were finding links between liver damage in plant workers and exposure to chlorinated hydrocarbons. For the next several decades, wrangling among health advocates, government, and corporate decision makers over the use of PCBs dragged on. Medical experts, scientists, and corporations had more than enough evidence that these agents were harmful, but workers, waterways, and food sources continued to be exposed. Finally, in 1979, EPA banned PCBs, but much damage had already been done.

However, it was the public outcry over PCB contamination arising from the grassroots efforts of residents along New York’s Hudson River that became the catalyst for real action. According to the New York Riverkeeper, a not-for-profit organization that advocates for water-quality issues, “Between 1947 and 1977 two General Electric (GE) capacitor manufacturing plants discharged an estimated 1.3 million pounds of PCBs into the Hudson River.” These contaminants are now “found in sediment, water and wildlife throughout the Hudson River ecosystem as far south as the New York Harbor” and “also found in people,” says Riverkeeper.

No Escaping the Legacy
“When these chemicals become part of the sediment of waterways, they enter the food chain, first through small organisms deep in the soil, then worms who consume them, then fish, and then humans,” explains Sowers. “As citizens saw the effect of contaminants with numerous deformities in fish, EPA took GE to task, ordering them to clean up the river. The plant was shut down, but the problem was that there were already so many [PCBs] they had seeped down into the shale and contaminated wells; the company had to pump the PCBs out from under the limestone.”

The cleanup involved the then-current practices of remediation—which Sowers says have changed little in the 21st century. They were tedious, invasive to the environment, cumbersome, and very expensive, involving dredging, hauling away of the sediment to a landfill, capping with clean sand, and sometimes incineration. The Hudson River remediation was a huge undertaking, costing billions of dollars, that is just now in the final phases of completion.

Even on a small scale, “these practices quickly run into millions” with complex strings of liability that can be nearly impossible to sever, explains Charles Edwards, town council member of Alta Vista, VA, a small town situated outside of Lynchburg. Alta Vista has a population of just under 4,000, and coming up with an extra $10 million to $11 million for remediation of the town’s pond contaminated with legacy PCBs is a daunting challenge at best. “Years ago, PCBs were widely used in industry, and one of the plants in this area apparently just flushed it into the sewer system, which ended up in our pond,” says Edwards. “It is a clay lined treatment lagoon for overflow, and there is no ingress or egress.” So what gets in stays in.

After much discussion, the town was considering dredging and hauling the sediment to a landfill, or incinerating it. “But what happens if you dredge,” says Edwards, “and let’s say the truck overturns on the highway, and the PCBs spill all over the road, the original owner—and that’s us—is still liable for it.” And once the sediment is transported to a landfill, should the landfill become insolvent and the owners skip town—”which is known to happen,” says Edwards—the original owner is still liable for whatever was dumped there.

There’s no escaping responsibility, and because some of the PCBs can take several decades to break down, it is a burdensome legacy.

Beyond these problems, the interventions disturb the environment, not only affecting the habitat of wildlife and plant life but also allowing some of the PCB-laden sediments to escape and make their way into other regions.

Turning the Corner for a Permanent Solution
The unsatisfactory outcomes of current remediation have been a factor in Sowers’ investigations. For the last two decades, he has been spearheading scientific research into the microbes of sediments contaminated with PCBs, with the idea that eventually there would be a clue to breaking down these agents and eliminating them from the environment once and for all. “It was known that if you took the sediments and put them in a bottle without oxygen, the PCBs would lose most of their chlorines, but nobody knew why,” he says. Early on, GE spent a lot of money looking for microbes that would break down the harmful agents, but Sowers says that at the time, science did not offer today’s sophisticated technologies to analyze DNA.

By the late 1980s, instruments for polymerase chain reaction (PCR) assays were becoming available, which allowed researchers to clone DNA for investigations, a technique Sowers and collaborator Harold May, Ph.D., at Medical University of South Carolina used to begin unlocking the secret to PCB destruction. Sowers explains this was the stepping stone that started the path to achieving his latest results, reported in late 2015, which by all accounts will revolutionize PCB remediation—in terms of expense, time, and sustainability.

IMET: A Case for Basic Science Research
Russell Hill, Ph.D., director of IMET, says the name truly embodies what the organization does in its research labs headquartered in Baltimore and in collaboration with partners around the world. “We’re called the Institute of Marine and Environmental Technology, which means we do research, but our focus is on developing technologies that get this research where it is useful and practical.”

Sowers’ work, Hill says, is a prime example of what IMET does. “Kevin [Sowers] has been working for 20 years, putting in the first hard slug of understanding the basic biology of microbes breaking down the PCBs. It’s taken two decades to get to the point where it’s really paying off now in a big way.”

Hill adds that Sowers’ work is one of the exciting examples that has “reached the stage for prime time, and for commercialization,” and efforts that began in 1991 are “now ready to transfer that technology into the real world.”

IMET illustrates how public funds that support basic science can lead to solving important environmental problems affecting public health, safety, and our crucial natural resources. “We are supported by the University of Maryland state system, so we receive our funding from taxpayers, and our world-class faculty works hard to spend these dollars wisely and to also pursue private sources for additional grants,” says Hill.

“When we explained our research and how it is leveraged toward practical applications, other agencies such as the National Science Foundation, the National Institutes of Health, and the Department of Defense all stepped up to fund our efforts.” Better food safety, for example, can be achieved by making marine life safe to harvest as a food source when PCBs are eliminated from the water column.

Many Test Tube Results Later…

Sowers describes the transition from test tube to the real world that began in the early ’90s.

What the team learned was that the majority of harmful PCB variants were deep in the sediments of waterways, remaining stable and unaffected by the lack of oxygen. However, they postulated that if they used the right anaerobic bacteria—the ones that live without oxygen—and introduced them to the deep sediments, the PCBs would be dechlorinated by those bacteria, rendering them susceptible to complete degradation by oxygen-utilizing (aerobic) bacteria. It was an exciting concept, but it posed logistical dilemmas. How do you get the bacteria there? And which ones will do the best job?

“We began by putting sediment in containers without oxygen and started hitting them with different things and using PCR to see who was and wasn’t there,” he says.

This process narrowed down to a group of microorganisms known as halorespiring bacteria that in effect “breathe” the PCBs much as we breathe oxygen. Once these bacteria were identified, the team was able to learn what the organisms liked and didn’t like.

“By the mid-’90s, the Office of Naval Research [ONR] got interested in supporting our work. They were cleaning up bases and harbors and were very interested in sediments,” explains Sowers. “Once we found that using organisms under different scenarios was the key to destroying the PCBs, we had come full circle. We knew that we can’t control the oxygen—the lower part of the sediment will be anaerobic and the upper part aerobic. However, benthic organisms such as worms that occur naturally in the sediment continually mix the anaerobic and aerobic regions of the sediment so that both processes can occur together. The worms also performed as a transport system to get the bacteria to their destination.”

But working with worms in jars in a lab under ­controlled conditions isn’t like the real world.

Taking Science to a 6-Acre Petri Dish
Getting the microbes to showcase their talents required a boost from another collaborator. Enter Upal Ghosh, PhD, professor of chemical, biochemical, and environmental engineering at the University of Maryland. Ghosh’s research on activated charcoal had proven that this agent effectively binds PCBs and other hydrophobics (materials that repel water) to keep them out of the food chain. “We have shown through lab and field studies that introducing a strong sorbent like activated charcoal into sediments works in reducing PCB uptake in fish,” he says. The charcoal with its highly porous surface acts as a harvester to collect molecules; adding bacteria along for the ride was another stroke of genius.

In 2013, results of their research, “Remediation of Polychlorinated Biphenyl Impacted Sediment by Concurrent Bioaugmentation with Anaerobic Halorespiring and Aerobic Degrading Bacteria,” was published in the peer-reviewed journal Environmental Science and Technology.

In short, the investigators’ research in bioremediation—using bacteria to do the job—found that highly chlorinated PCB congeners within sediments could be rendered harmless. But it’s a two-step process. First, the deep sediment must be exposed to the anaerobic bacteria, which changes the chemical to a less-chlorinated version. This variant is then susceptible to different, aerobic bacteria.

In the study, the researchers reported that using activated carbon as the delivery system and introducing the two bacteria simultaneously resulted in an 80% decrease by mass of PCBs, from 8 to less than 2 mg/kg after just 120 days.

Funded by a grant from EPA, Ghosh has now developed a delivery system made of activated charcoal pellets, called SediMite, and is a partner in a startup company that has licensed the technology from the University of Maryland and Stanford to commercialize this technology. “SediMite is an agglomerate made up of active carbon, clay, and sand, and makes it convenient to apply the material to sediments in large scale,” says Ghosh. He explains that the collaboration with Sowers is allowing PCB-degrading organisms to be inoculated onto the pellets, which are about the size of typical half-inch wood stove pellets.

“If you just put activated charcoal in the water, it would float, but because the pellets have the clay and sand binder, they sink down and then break down over hours or days. Through the burrowing activities of organisms, such as worms, that live on the bottom surface, the microorganisms from the pellets are naturally worked into the surface biologically active sediment layer.”

First, the PCBs are absorbed by the activated charcoal, which removes them from the food chain. Next, the microorganisms, which Ghosh says are “effectively riding on the activated carbon backbone of the SediMite pellets,” degrade those absorbed PCBs.

Small studies led to the team testing the bioremediation process on PCB-contaminated sediments in freshwater wetlands, an estuarine harbor, and a river. When they used gas chromatography and PCR analysis to measure results, they found a 70–80% PCB reduction in just three to six months. This success in such a short time led to the launch of phase 2 tests, including a four-month study in the “6-acre petri dish”—the watershed drainage creek leading to the Potomac River on Marine Corps Base Quantico near Richmond, VA.

Sowers describes how the pellets can be broadcast by a delivery system that uses a compressed-air venturi loader, a machine typically used to deliver air into manholes for workers or to deliver granulated material during various manufacturing processes. The venturi, which looks like a large airhorn, was modified to suck up the pellets, which were then sprayed out over the water. “We applied a total of three tons in three treatment plots; the typical dose is about one pound per square foot, and you can scale that up or down,” he says.

The Quantico test project began in May 2015, and after four months researchers retrieved sediment core samples for analysis in mid-October. By early November the preliminary results from analysis were in and “demonstrate the bioremediation definitely has an effect on PCB levels in the field,” says Sowers. “We observed 25% and 36% reduction of PCB levels in the two treated plots. This is only four months after treatment,” he says. “In contrast, there was no change in PCB levels in both the untreated plot and the plot treated with SediMite and not bioamendment.”

Sowers says another analysis will be conducted in spring 2016 to examine further effects of treatment and potential degradation over time.

Green, Clean, and Effective
The consensus of all investigators is that the bioremediation process is an effective “green” remediation that is cost-effective and environmentally sustainable for treating persistent organic pollutants like PCBs. “People are really excited about this,” says Ghosh, because “we don’t have any way to degrade these in situ except very slowly, and that can take decades and possibly longer. People are waiting for this because this technology can reduce the exposure to the ecosystem.” The application process is simple and does not require dredging cranes, dump trucks, or heavy equipment.

Conventional remediation, as Ghosh points out, is not only expensive, but “when you add a foot of clean sand over contaminated sediments, yes, that is helpful, but the problem is you are covering organisms that are living there. This can ruin wetlands as it raises the water level.

“Dredging is also cost-prohibitive for large areas of contamination in rivers, lakes, and coastal sediments, to say nothing of the disruptive potential of this intervention.”

Pick Up Your Fork and Say Aaah!
The new technology of bioremediation promises to give PCB-contaminated sites a new lease on life and, as Sowers says, “remove the cloud of doubt” about eating fish from many of our waterways.

Although sediments in some contaminated areas show deceptively low levels of PCBs, he says this is “because the newer sediments coming to cover them are cleaner at the top, but they [PCBs] are still there and can be potentially consumed by organisms and rise to the surface and be eaten by fish and people.”

He notes, “There are Maryland fish consumption advisories in a number of bodies of water, and ultimately, one would like to use all our natural resources and lift those consumption advisories.”

While PCBs are a global problem, these bioremediation technologies are not a dream of the future—they are here now and might be the key to lifting advisories in places where the food chain is being threatened. This is good news for municipalities, industries, and environments the world over whose food chain and public health continues to be plagued with legacy PCB contamination.