Human Visual Function in the North Carolina Clinical Study on Possible Estuary-Associated Syndrome
Hudnell, HK et al., (2001) J Toxicology and Environmental Health, 62:575-594.
The U.S. Environmental Protection Agency assisted the North Carolina Department of Health and Human Services in conducting a case study to investigate the potential for an association between fish kills in the North Carolina estuary system and the risk of persistent health effects. Impetus for the study was recent evidence suggesting that estuarine dinoflagellates including members of the toxic Pfiesteria complex (TPC), P. piscicida and P. schumwayae, may release a toxin(s) that kills fish and adversely affects human health. This report describes one component of the study in which visual system functions was assessed. Participants working primarily in estuaries inhibited by TPC or in offshore waters thought not to contain TPC were studied. The potentially exposed estuary (n=22) and unexposed offshore (n=20) workers were matched for age, gender and education. Visual acuity did not differ significantly between the cohorts, but visual contrast sensitivity (VCS), and indicator of visual pattern-detection ability for stimuli of various sizes, was significantly reduced by about 30 % in the estuary relative to the offshore cohort. A further analysis that excluded participants having a history possibly predictive of neuropsychological impairment showed a similar VCS reduction. Additional analyses indicated that differences between the cohorts in age, education, smoking, alcohol consumption, and total time spent on any water did not account for the difference in VCS. Exploratory analyses suggested a possible association between the magnitude of VCS reduction and hours spent in contact with a fish kill. The profile of VCS deficit across stimulus sizes resembled that seen in organic solvent-exposed workers, but an assessment of occupational solvent, and other neurotoxicant, exposures did not indicate differences between the cohorts. These results suggest that factor(s) associated with the North Carolina estuaries, including the possibility of exposure to TPC toxin(s), may impair visual system function.