Commercial fishermen do not face significant health risks from routine occupational exposure to Pfiesteria in estuaries

Apr 19 2006

Commercial fishermen do not face significant health risks from routine occupational exposure to Pfiesteria in estuaries. According to a study recently accepted for publication by Environmental Health Perspectives, researchers found no correlation between specific human health effects in "watermen" (commercial fishermen) and low-level exposure to the dinoflagellate Pfiesteria in areas of the Chesapeake Bay.

In the summer of 1997, a group of watermen working on the Pocomoke River off the Chesapeake Bay developed a pattern of deficits in learning and memory after exposure to areas that had been associated with several fish kills, which some scientists say were caused by Pfiesteria outbreaks. Research personnel studying Pfiesteria in the laboratory similarly reported neuropsychological deficits after exposure.

But less is known about the health risks of chronic, low-level exposure to Pfiesteria strains, which typically are found in estuaries of the U.S. mid-Atlantic region in the summer and fall. The current study is the first systematic, multiyear effort to correlate human health effects with exposure to waterways where Pfiesteria has been clearly documented.

The research team followed 88 watermen and 19 controls over a total of four years (1999–2002). Watermen averaged 10 hours or more per week on Maryland Chesapeake waters or tributaries. Controls - community members matched to the watermen by zip code, age, and educational level - had minimal contact with estuarine waters.

Study subjects were questioned biweekly about any symptoms, the amount of time they had been exposed to waters, and whether they had been exposed to any chemical toxicants. They underwent neuropsychological testing at the beginning and end of each year's summer fishing season. The two-hour tests were designed to assess a variety of cognitive functions that Pfiesteria research suggested could be affected by exposure.

The researchers analyzed more than 3,500 samples collected during the study period from the water column throughout the region where the watermen worked. Each year, Pfiesteria was most prevalent during the late summer and early fall, and then dipped below detection levels in the winter.

The reseachers found no correlation between the watermen's work in any area where Pfiesteria was identified and any specific changes on tests or reported symptoms. The scientists point out that unique, isolated outbreaks of Pfiesteria or unusually toxic strains of the organism could plausibly cause human health effects. Absent these conditions, however, watermen do not appear to face significant health risks during routine occupational exposure to waters where Pfiesteria is found.

The lead author of the study was J. Glenn Morris of the Department of Epidemiology and Preventive Medicine, University of Maryland School of Medicine, Baltimore. Other authors included Lynn M. Grattan, Leslie A. Wilson, Walter Meyer, Robert McCarter, Holly A. Bowers, J. Richard Hebel, Diane L. Matuszak, and David W. Oldach.

The article is available free of charge at http://www.ehponline.org/docs/2006/8627/abstract.html.