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Des Moines Register: UI Team Fears PCBs May Remain Cause for Concern
Sunday, December 6, 2009
By David Elbert
PCBs, the toxic chemicals banned in the 1970s, are back.
Actually, PCBs never went away, and researchers at the University of Iowa are trying to figure out how big of a problem that is and what can be done about it.
â€¨â€¨When polychlorinated biphenyls were first discovered in the 1920s, they were considered a miracle additive. They never broke down, which made them great for industrial uses including lubricants, coolants, flame retardants, hydraulic fluids and pesticides. PCBs were added to products as diverse as electrical wiring and carbonless copy paper.
We began to discover in the 1940s that they were also harmful. It was a slow learning curve, but eventually science and industry agreed on two things.
â€¨â€¨When PCBs entered the human body, they could trigger cancer, as well as problems with the nervous system and thyroid.
â€¨â€¨We also learned that their heavy molecules accumulated in humans and other living things, including the food we eat. Someone who ate a fish that contained PCBs could carry those PCB molecules around in his or her body forever.
By the 1970s, the evidence of harm persuaded officials to ban the use of PCBs in all but a handful of controlled uses.
â€¨â€¨End of story, pretty much. Until now.â€¨â€¨
Now, researchers in Iowa City and elsewhere have reason to believe that PCBs are continuing to accumulate in places like Lake Michigan, and probably elsewhere.â€¨â€¨
One possibility being investigated by a U of I team involves PCB11, a lighter-weight molecule that is present in the air around Chicago.
"There are 209 different types of PCBs, and they all have different types of health-related toxicologies," said Keri Hornbuckle, a professor of civil and environmental engineering at the U of I.
â€¨â€¨"We don't know exactly where PCB11 lies in that, although my colleagues here at Iowa have begun to test for that," she said.
â€¨â€¨The original PCB problem was believed to involve only heavy PCB molecules that were less likely to be airborne. Those PCBs seeped into soil or water when a spill occurred. They were absorbed by growing plants and then accumulated in the tissues of animals that ate the plants.
PCBs are known to be present in paint, Hornbuckle said. They are byproducts of paint manufacturing. In fact, when the 1970s ban on PCBs was put in place, there was an exemption for the small amount present in paint, because it was not believed to be a problem.â€¨â€¨
But now, Hornbuckle said, scientists are learning "our original assumptions of 30 years ago are not all correct." All PCBs "have a capacity to go into the air," she said.
â€¨â€¨PCB11 became a focus after Hornbuckle's team discovered the compound to be higher than many other PCBs in Chicago air.
Hornbuckle's first study found wide distribution of PCB11 in Chicago air. It noted that there were several paint manufacturers in the Chicago area.â€¨â€¨
A second study by Hornbuckle's group found PCB11 in air around Cleveland. Studies by others found PCB11 in the air of polar regions and elsewhere, leading to the conclusion that its presence is a global issue. It also can be found "in consumer products, like cereal boxes and newsprint," Hornbuckle said.
"We think it's in commercial paint pigment," she said.â€¨â€¨
So she did a pigment study.
â€¨â€¨"We purchased commercial pigments from three major companies that sell house paint here in Iowa City, and we analyzed about 30 different pigment types and found PCBs in many of them," she said.â€¨â€¨
The results were published last week online in the journal of Environmental Science & Technology.â€¨â€¨
The study found low levels of several different types of PCBs in the paints. PCB11 was the most frequent.
"To our knowledge, pigments or dyes are the only significant source of PCB11," the study said.
â€¨â€¨It concluded, "The elevation of PCB11 in the air must be associated with human activity utilizing pigments or dye."â€¨â€¨
It was not clear how PCB11 got from paint into the air, the study said, although one theory is that over time the molecules from painted surfaces vaporize into the air.â€¨â€¨
"You should make it clear that we are not suggesting that paint is toxic," Hornbuckle said last week.
Finding PCBs in paint is not like finding lead, which was banned from paint manufacturing decades ago, and which is still considered dangerous when found in older homes.â€¨â€¨
The fact that PCBs are in paint is no surprise to paint manufactures or scientists, she said - "what's surprising is that our findings may explain what we saw in air."
â€¨â€¨"There is very little evidence that breathing them is a problem," she said.
â€¨â€¨The more likely problem is that PCB11 in the air around Chicago, Cleveland and other industrial cities eventually settles into water, such as Lake Michigan, where it is consumed by fish that are then eaten by people.
The comforting news, for now at least, Hornbuckle said, is that lighter-weight PCBs, including PCB11, are more easily metabolized by animals and humans. "The details are not clear," she said. "We don't know whether it's a lot more or a little more."
â€¨â€¨In fact, Hornbuckle said, right now the main problem is a lack of information.
â€¨â€¨"We need to understand: Do they accumulate in fish? Can they be deposited in nearby waters? Is there an inhalation exposure problem? How much of what's in paint gets into the air? If it metabolizes, are the products of metabolism toxic? Because PCBs do metabolize into other toxic chemicals.
"There's quite a lot of interesting research questions to come out of this.
â€¨â€¨"How it all adds up in a human is really a hard question because we live such a long time and these effects are the result of long-term exposures," she said.