CHAMPAIGN, Ill. -- Preliminary but cautiously given good news for aging Great Lakes fish-eaters: First-round tests of fine motor skills showed barely a hint that years of consuming PCB- and DDE-contaminated fish have had any negative effects.
The study, when completed, will provide a rare, comprehensive look at the effects of environmental contaminants on older people. Scientists began a neurological assessment in 1992 of a group of men and women older than age 50 who have consumed 24 or more pounds of sport-caught Lake Michigan fish annually since the 1960s. A comparable group from the same region who didn't eat fish also is being studied. The fish-eaters have elevated levels of several contaminants, including PCBs and DDE (a derivative of the pesticide DDT).
Preliminary test results of dexterity and hand steadiness were presented May 12-15 in Montreal during Health Conference '97, which was devoted to pollution of the Great Lakes Basin. An overview of the project -- funded by the Agency for Toxic Substances and Disease Registry of the U.S. Department of Health and Human Services -- was published last year in the journal Toxicology and Industrial Health.
"People eating fish in the 1960s and '70s were really getting the highest level of exposure," said principal investigator Susan L. Schantz, a professor of environmental toxicology at the University of Illinois. "PCBs and DDE are not very easily metabolized; they tend to accumulate in body fat."
Animal research has shown that PCBs (polychlorinated biphenyls) -- a group of industrial chemicals toxic in the environment -- decrease dopamine levels in the brain. In Parkinson's disease, too little dopamine contributes to a reduction of motor function and executive abilities (planning and attention).
"We thought that we might see reduced motor function," she said. "At this point, however, it doesn't look like it. We've only looked at two of a large number of tests that we have yet to analyze. We've identified one aspect of nervous system function that seems not to be affected. But we saw what appeared to be a trend for the most highly exposed individuals to do more poorly, so we need to be cautious."
The findings initially showed slower times in hand-dexterity and hand-steadiness tests by the
fish-eaters, but after accounting for unrelated factors such as arthritis and medications, the differences dropped below statistical significance. The same tests will be repeated in three years. Meanwhile, the researchers are analzying tests of the subjects' memory, executive functions, and visual and spatial abilities.
PCBs and DDE have been the most commonly occurring contaminants in the Great Lakes. While their levels have dropped dramatically since 1970, they remain unacceptably high, according to health officials, who continue to issue advisories on fish consumption.
Working with Schantz are Harold E.B. Humphrey and Marvin L. Budd of the Michigan Department of Community Health; Anne M. Sweeney of the University of Texas Health Sciences Center at Houston; Joseph C. Gardiner, Donna M. Gasior and K.R. Srikanth of the College of Human Medicine at Michigan State University; and psychologist Robert J. McCaffrey of the State University of New York at Albany.