Polychlorinated biphenyls, known as PCBs, were widely used in the United States in electric and cooling systems between the 1930s and late '70s. Used in all types of flame retardants, solvents, adhesives, and flame retardants, PCBs were ultimately linked to health problems like cancer, though it took several decades for scientists to establish the link.
Although they've been banned for 30 years now because of their negative health effects and ability to accumulate in the environment, the stubborn chemicals persist and can build up in animals and people over time.
In a first-of-its kind study published in the journal Environmental Health Perspectives, researchers from the University of Montreal have linked the persistent chemical to motor and mental functioning, too, providing more evidence that PCBs act as neurotoxic compounds. Interesting, this study looked at levels of PCBs that people in the U.S. currently experience. (Many previous studies looked specifically at people with high exposure, such as fisherman in areas contaminated with PCBs.)
In the study, Canadian researchers looked at data from 708 people between the ages of 60 and 84. They found that as PCB levels rose in the older adults—particularly older women—cognitive functioning scores were worse, indicating poorer motor skills, memory, and information processing.
"We found that the difference between the low exposure and the high exposure groups was similar to nine years of normal aging in women age 70 to 84 years, the group most affected," Bouchard points out.
The research is important because it suggests a lifetime of exposure—not just exposure during critical points in childhood development—can cause neurotoxic effects. "While most studies have looked at the impact of PCBs on infant development, our research shows that this toxin might affect us throughout our lives," says Maryse Bouchard, PhD, assistant professor of environmental and occupational health at the University of Montreal and the study's lead author. "Aging persons could be at particular risk because of higher cumulative exposure built up across a lifetime; susceptibility due to underlying medical conditions, such as vascular disorders; and diminished cognitive reserve capacity. Our present findings suggest that PCBs, even at levels generally considered to pose low or no risk, may contribute to cognitive deficits."
The high levels could be explained by a few factors:
• The contaminates bioaccumulate throughout a lifetime
• Older people may have experienced higher exposure levels because PCBs were more widely used decades ago before they were tightly regulated
• Older people's neurological systems may not be able to compensate for toxic exposure as well as younger people's.
Interestingly, women may be more affected than men because PCBs are potential hormone-disrupting chemicals. Certain hormones, such as estrogen, are important for optimal cognitive functioning, and PCB exposure could throw off optimal hormone levels.
Since PCBs build up in the tissue of animals, people can reduce exposure by cutting back on animal products like meat, butter, and other dairy products. While eating fish brings many health benefits, such as improved brain functioning, it's important to eat fish lower on the food chain because PCBs often accumulate in larger fish, as mercury does. (Check the Environmental Protection Agency's fish advisories.)
Beyond that, Bouchard says there's not much people can do to reverse high PCB levels—or even an affordable test to assess an individual patient's PCB levels.
Instead, she says, we need to ensure that PCBs are properly discarded, and that contaminated sites are remediated. One bright spot? PCB levels have dropped in younger generations, meaning this type of brain damage may well become a thing of the past.