New health concerns linked to Pfiesteria Study by EPA scientist of N.C. fishermen finds problem with vision

September 18, 1998|By Timothy B. Wheeler | Timothy B. Wheeler,SUN STAFF Sun staff writer Heather Dewar contributed to this article.

The toxic microorganism blamed for fish kills in the Chesapeake Bay and elsewhere along the East Coast may cause visual impairment among exposed fishermen and swimmers that could make them more prone to accidents, a federal scientist said yesterday.

Kenneth Hudnell, a neurotoxicologist with the U.S. Environmental Protection Agency, said tests conducted on fishermen in North Carolina last fall found preliminary evidence that those who worked in waters where Pfiesteria-related fish kills have occurred had a reduced ability to detect visual patterns -- compared with other anglers plying uninfested areas.

With a reduced ability to distinguish between light and dark, Hudnell said, "everything will look much less distinct. . . . That's why you have a greater risk of accidents."

If confirmed, the EPA scientist's finding represents a new and more lasting health problem attributed to Pfiesteria, in addition to the short-term memory loss and confusion found by a Maryland medical team among people exposed to fish kills on Chesapeake Bay last year.

The EPA scientist said further study is needed to verify whether his findings are a result of Pfiesteria exposure or some other as-yet unknown factor. Maryland researchers, however, reacted enthusiastically.

"It's very significant, from a scientific point of view," said Dr. Lynn Grattan, a University of Maryland neurologist.

She is a member of the state medical team that found watermen and others exposed to fish kills on the lower Eastern Shore last year had trouble remembering numbers or what they had just done. The difficulties eased a few months after the exposure stopped, however.

"The things I assessed got better, and the things Dr. Hudnell was looking at show a lingering long-term effect," Grattan said. "That's certainly pointing us in new directions with our studies."

Grattan said the visual tests conducted by the EPA lab now have been added to the battery of exams being used by Maryland medical reserachers.

Hudnell, who works at EPA's health and environmental effects laboratory in Research Triangle Park, N.C., tested North Carolina fishermen as part of a task force assembled by that state to find out if residents there were suffering health problems from exposure to Pfiesteria. The elusive microbe has been blamed for massive fish kills in that state.

The task force reported in June that it had not found any other health effects. But the EPA scientist said his findings were not included in the earlier report so they could undergo additional analysis.

Hudnell said he had tested two groups of fishermen: 22 who had worked in rivers where there had been fish kills and 20 others who lived on the Outer Banks and worked offshore, where problems with Pfiesteria have not been reported.

Fishermen in both groups showed no difference in their visual acuity, when asked to identify increasingly smaller rows of black numbers displayed on white cards.

But fishermen likely exposed to Pfiesteria showed reduced sensitivity to contrast when given another type of test. In that one, subjects are asked to describe patterns on cards displaying a series of dark and light bars, with each set of bars having less contrast between them.

Hudnell said the vision impairment he saw in the fishermen is similar to what he has seen in other studies of people exposed to toxic chemicals, such as solvents.

He said the tests found that exposed fishermen had 30 percent less ability to detect the contrasting visual patterns. He likened it to needing to adjust the contrast on a television set to make the picture sharper.

"The image is not near as distinct, but you can still see it," he said. "These people are not walking into trees." But Hudnell added that research has shown that decreased sensitivity to contrast can increase the risk of accidental injury.

"You won't be able to see as much from afar, you won't be able to see as well up close," he explained. "If you can't see it, it takes longer to detect and react to it."

People naturally lose some ability to detect contrasting patterns as they age, the scientist said. He took that into account by excluding test results of people whose medical problems or other factors, such as alcohol and tobacco use, might influence their vision. The final results were based on 14 exposed fishermen and 10 "controls" who supposedly had not been around Pfiesteria.

Maryland officials reacted to Pfiesteria outbreaks last year by closing parts of three rivers after discovering large numbers of dead or dying fish, most of them menhaden, with sores on them typical of those caused by the toxic microbe. Some complained afterward that the state overreacted and contributed to a public hysteria that saw sales of seafood plummet.

Pub Date: 9/18/98

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