Heavy Consumption Of Tainted Fish Curbs Adult Learning And Memory

Since 1992, researchers, led by Susan L. Schantz of the University of Illinois College of Veterinary Medicine, have studied Lake Michigan fish-eaters, many of whom regularly had eaten more than 24 pounds of sport-caught fish a year. The researchers’ latest findings show that the heavy eaters who are now over age 49 have problems learning and remembering new verbal information.

"This study suggests, for the first time, that PCB body burdens in adulthood may be associated with impairments in certain aspects of memory and learning," Schantz said. "The focus has been almost exclusively on increased health risks of exposure to children and pregnant women. It had been assumed that mature adults are less susceptible than are developing fetuses. This may not be the case." PCBs were widely used – until banned in the late 1970s – as electrical insulators and lubricants and as extenders in paints and varnishes. The chemicals decompose slowly and are virtually non-biodegradable. Large quantities remain in older electrical equipment still in use. In the Great Lakes, PCBs make their way up the food chain and accumulate at increasing levels in fatty tissue. The new study by researchers at four institutions is to go on line June 5 and appear in print in the June issue of Environmental Health Perspectives, a journal of the National Institutes of Health. They also found elevated levels of DDE (a breakdown product of DDT), lead and mercury in the heavy fish-eaters, but the only negative effects were tied to blood serum levels of PCBs.

Fish-eaters with high blood PCB levels had difficulties recalling a story told just 30 minutes earlier. They also were less likely than their less-exposed peers to cluster words given orally into categories based on their meaning to boost recall, said Schantz, a professor of toxicology in the department of veterinary biosciences. Researchers used the Weschsler Memory Scale and the California Verbal Learning Test, both standard tools for measuring cognitive abilities.

In the 1990s, Drs. Joseph and Sandra Jacobsen of Michigan’s Wayne State University reported that exposure to low levels of PCBs disrupted fetal brain development, leading to neurological abnormalities and learning disabilities, including memory deficits, in affected children.

Schantz previously reported that high levels of PCBs in adult fish-eaters resulted in barely a hint of problems with fine motor skills such as dexterity and hand steadiness. In the latest work, researchers also did not find statistically significant problems with many other cognitive abilities, such as executive function (planning and attention) and visual-spatial function.

Researchers in the study were from the UI, Michigan State University, the State University of New York at Albany and the University of Texas Health Science Center at Houston.