Scientists still don?t know what caused neurological disorders in dozens of people swimming and working in pfiesteria-infested waters on the Eastern Shore nine years ago, but a study released by the University of Maryland School of Medicine found watermen are at little risk today.
Commercial fishermen do not face significant health risks from occupational exposure to pfiesteria in the Chesapeake Bay, according to the study, published in the July 2006 issue of the Environmental Health Perspectives journal.
“In isolated instances, pfiesteria may cause health problems when a person is exposed to high concentrations or unusually toxic strains of the organism,” says Dr. J. Glenn Morris, M.D., chair of the Department of Epidemiology and Preventive Medicine at the University of Maryland School of Medicine and lead author on the study. “But our study was the first to investigate the effects of consistent, occupational exposures, and we found that watermen who have this low-level exposure to pfiesteria strains are not at increased risk for illness.”
In short, Morris said, they do not know why people developed symptoms ? including problems with memory and learning ? after exposure to water in three eastern shore streams in 1997.
Morris and the university continue to monitor those individuals.
“What I can say is within six months of the initial outbreak, people … had returned to normal lives,” he said.
State researchers still do not know why the pfiesteria piscicida population exploded in 1997 or why it has remained under normal levels since.
“We find it every year. In the past several years there hasn?t been any prevalence. We haven?t associated it with any fish outbreaks or fish kills,” said Dave Goshorn, director of the Resource Assessment Service of the Department of Natural Resources.
In the university study, Dr. Morris and his team followed 88 watermen who averaged 10 hours or more per week in and around the Chesapeake Bay between 1999 to 2002. They underwent neurological testing and answered questions about symptoms and exposure.
“When compared to individuals without exposure to pfiesteria, we found no difference in the neurological functions or symptom patterns among the watermen we studied,” Dr. Morris said.
The research team also analyzed 3,500 water samples from areas where the watermen worked. pfiesteria was more prevalent during the late summer and early fall and undetectable during the winter, the study found. The findings support similar studies in North Carolina and Virginia that did not find significant health risks for watermen.
The U.S. Centers for Disease Control and Prevention funded the Maryland study. Morris said with new detection and diagnostic instruments they are ready if another outbreak should occur.
