PCBs: A Disturbing Legacy and Ongoing Threat
PCBs were outlawed in the 1970s — so why don’t levels keep going down?
Unfortunately, PCBs are almost everywhere.
IIHR Research Engineer Keri Hornbuckle is well aware of how thoroughly PCBs have permeated our environment. What she wasn’t expecting to find was PCB11 — which had rarely before been reported — in the air near Chicago.
Polychlorinated biphenyls (PCBs) were banned by law in 1976. Hornbuckle had never found PCB11 in the 25 years she has spent studying the chemical compounds. Why would it suddenly turn up now?
“I was quite sure we had made a mistake,” Hornbuckle says.
A Troubling Legacy
IIHR Assistant Research Scientist Dingfei Hu (now at Smithers Viscient near Boston) had indeed found PCB11. Working with Hornbuckle and Andres Martinez (then a PhD student), he went on to conduct a detailed literature search and additional research to prove it. Using new methods and new analytical standards, Hu published several papers on the subject of non-legacy PCB11. The findings were a surprise to the scientific community that studies PCBs. But the discovery quickly led to worrying questions. Where did the compound originate? Was it increasing, and if so, why?
Hornbuckle and Hu are part of a research center at the University of Iowa, the Iowa Superfund Research Program (ISRP), which focuses on the sources, exposures, and toxicities of PCBs in the environment. The center is funded by the National Institute of Environmental Health Sciences, part of the National Institutes of Health.
Hornbuckle, who is also a professor of civil and environmentalengineering, says ISRP is a powerful collaboration. The multidisciplinary center brings together scientists with expertise ranging from engineering to toxicology, microbiology, radiology, public health, chemistry, and more.
“That’s one of the great things about the center,” she explains. “What we learn as engineers and chemists gets used to promote excellent science in other areas. It’s really exciting.”
A Painstaking Search
Researchers had for years assumed that all PCBs in the environment were “legacy PCBs,” produced before the chemical compounds were banned in 1976. After the ban, PCBs in the environment decreased sharply — but then the decreases slowed down and leveled off. Researchers wondered — why don’t PCB levels keep going down?
The evidence seemed to point to a more current source. Hu, an analytical chemist, began a laborious process of detective work, matching up identified PCBs with possible sources. Almost 10 years earlier, scientists in New York had found PCB11 in water near a paint plant, and Hu suspected the source was current paint pigment production. He set out to prove this startling idea by analyzing pigments he bought at a local home improvement store. He found PCB11 and 50 other compounds, including toxic dioxin-like PCBs. It was a surprising discovery for the whole team. Since PCBs had been banned for decades, Hornbuckle wasn’t expecting to find them in products currently being sold and widely used. How did this happen?
A Loophole Exposed
Hornbuckle says that EPA rules appear to exempt pigments and dyes from the prohibition of PCB production. Considering how many products use paints, pigments, and dyes, this rule could have had a major impact.
Pigments are everywhere — from plastic bags and packaging to newspapers, magazines, and more. Now, we realize these pigments can bring PCBs with them. “We know that the magnitude of release is so large that PCB11 and perhaps the other PCBs that are in paint may equal the contribution from legacy PCBs,” Hornbuckle says.
Hornbuckle says she’s impressed by Hu’s determination to uncover non-legacy PCBs. “This part is very clever,” Hornbuckle says. Using his findings from individual PCBs in specific pigments, as well as limited literature reports, Hu was able to deduce most of the proprietary processes the industry uses to produce the PCB-laced paint.
‘PCBs are Nasty’
Once PCBs are in our bodies, some of them accumulate. Some are also metabolized to other chemicals, or flushed. The most common entry method is in the food we eat. “Old, large, fatty fish are the worst,” Hornbuckle says. “You could get a lot of PCBs in a single meal.” Once PCBs are in the lower food web, they build up, or biomagnify.
The materials used to build and finish our homes also contribute PCBs to our bodies. Homes, schools, and other buildings built between 1930 and 1970 could include caulking, paint, and electrical equipment with high levels of PCBs. Remodeling done after the 1970s can reduce PCB levels a great deal. Since PCBs affect our hormones, they can have a variety of negative health effects. PCBs are fat soluble, can mimic hormones and act as endocrine disrupters, interfering with the reproductive systems of mammals and birds. Some PCBs are very persistent, and can be passed from mother to child through several generations. For vulnerable populations, such as developing fetuses, PCBs can act as a neurotoxin. They are also known carcinogens.
“That’s pretty scary,” Hornbuckle says. “Toxicologists don’t know what makes one person get cancer, and another person not. They also don’t know exactly how these chemicals affect the development of babies.”
At some point, Hornbuckle says, it’s up to the public to decide if the cost of eliminating PCBs is worth it. If trace levels of PCBs were no longer allowed, paint and other products might be more expensive. Certain dyes might be unavailable or less permanent.
Is It Worth It?
Hornbuckle is hopeful. “I think publicizing this science has a potential to make a change,” she says. “I think it’s going to make a difference.”