Study: Routine, Low-Level Exposure To Pfiesteria Doesn't Pose Significant Health Risk

Researchers from the University of Maryland School of Medicine said they found that people do not face significant health risks from routine, low-level exposure to Pfiesteria.

They said their study, published in the July issue of the journal Environmental Health Perspectives, is the first systematic, multi-year effort to correlate human health effects with exposure to waterways where Pfiesteria organisms have been clearly documented.

"In isolated instances, Pfiesteria may cause health problems when a person is exposed to high concentrations or unusually toxic strains of the organism," said J. Glenn Morris, MD, MPH & TM, professor and 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 (commercial fishermen) who have this low-level exposure to Pfiesteria strains are not at increased risk for illness."

In 1997, an illness outbreak of unknown origin occurred on the Pocomoke River in Maryland, making dozens of commercial fishermen sick. The state appointed a task force, led by Morris, to determine which organism caused the outbreak and whether or not that organism made the watermen sick. It was hypothesized that the dinoflagellate organism Pfiesteria was the culprit.

Morris and his team subsequently followed 88 commercial fishermen who averaged 10 hours or more per week on the waters and tributaries of the Chesapeake Bay in Maryland from 1999 to 2002. They were questioned twice a month about symptoms and exposure to water and chemical toxicants. The study volunteers also underwent neurological testing at the beginning and end of each year's fishing season. The tests were designed to assess a variety of cognitive functions that could potentially be affected by exposure to Pfiesteria, including sensory and motor function, attention and concentration, memory, and visual and verbal ability.

"When compared to individuals without exposure to Pfiesteria, we found no difference in the neurological functions or symptom patterns among the (commercial fishermen) we studied," Morris said.

The research team also analyzed more than 3,500 water samples that had been collected during the study period from areas throughout the region where the commercial fishermen worked.

"We found that Pfiesteria was more prevalent during the late summer and early fall and that it was undetectable during the winter," Morris said. "We also found that Pfiesteria species were widely distributed in the Chesapeake Bay region, suggesting that it is part of the 'normal' algal flora in estuarine areas. The question remains unanswered as to what caused the very real illnesses among persons with exposure to the Pocomoke River in 1997. However, the findings of our study support similar studies in North Carolina and Virginia in providing reassurance that watermen do not appear to face significant health risks from routine exposures to estuarine waters that contain Pfiesteria."

J. Glenn Morris:

This article originally appeared in the 07/01/2006 issue of Environmental Protection.

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