Baltimore's dirty industrial past often comes back to haunt us—chromium seeping into neighborhoods, arsenic in public parks, polychlorinated biphenyls (PCBs) in the waterways. Now, a University of Maryland professor may have found a micro-organism living on the sludge floor of Baltimore's harbor that actually thinks PCBs are like a fine cigar: They eradicate them by "breathing" them. It's a finding that could help other cities contend with their own polluted pasts.
PCBs, first used commercially in 1929 and composed of chlorine, carbon, and hydrogen, were used as cheap, reliable coolants and lubrications. When PCBs were found to be massively toxic, their use was halted in 1977, which is when their durability became a liability.
Dealing with PCBs usually involves capping the polluted area or dredging the waterways, neither of which is totally effective. PCBs are oily, so they attach themselves to fatty tissue and move up through the food chain through a process called biomagnification—extremely high concentrations can be found in marine mammals, such as whales, and as far away as the Artic.
Dr. Kevin Sowers, who works at the UM's Biotechnology Institute, first became interested in this mysterious micro-organism that feeds on PCBs when a fellow researcher, Dr. Hal May, started examining sediment from the Hudson River. The researchers knew there was something living deep in the sediment, where there was no oxygen, that was respiring and eliminating the chlorine in the PCBs. In 2001, Sowers, 53, identified the organism, which can only be seen under an electron microscope.
"The significance of this is that once you eliminate the chlorine, these [PCB] compounds become susceptible to breakdown," he continues. "That's what these organisms do—they strip off the chlorines in the process of respiring."
According to Sowers, the sticky, stinky sludge of Baltimore's harbor contains a particularly happy population of the micro-organism. "To them, this was a gold mine," he says. Sowers has been busily shipping samples of the super sludge to other researchers such as Dr. Paige Novak, an associate professor at the University of Minnesota, who is conducting her own research into its pollution-fighting potential. "It's very exciting," says Novak. "Kevin was at the forefront. What he's done is find that an organism exists that breathes PCBs."
Now that the organism has been isolated, Sowers and other researchers are trying to find ways to magnify its PCB-consuming power so they can be put back into polluted areas to more efficiently respire the pollutant.
"We usually look at bacteria from the medical side and think they're bad, but most of them are good," says Novak. "These organisms could potentially clean up these PCBs that have been with us for 50 years."