Human visual function in the North Carolina clinical study on possible estuary-associated syndrome.

The U.S. Environmental Protection Agency assisted the North Carolina Department of Health and Human Services in conducting a study to investigate the potential for an association between fish kills in the North Carolina estuary system and the risk for 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 function was assessed. Participants working primarily in estuaries inhabited by TPC or in off-shore 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), an 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.

Estuary-associated syndrome in North Carolina: an occupational prevalence study.

Atlantic coast estuaries recently have experienced fish kills and fish with lesions attributed to Pfiesteria piscicida and related dinoflagellates. Human health effects have been reported from laboratory exposure and from a 1997 Maryland fish kill. North Carolina has recorded Pfiesteria-related fish kill events over the past decade, but human health effects from environmental exposure have not been systematically investigated or documented here. At the request of the state health agency, comprehensive examinations were conducted in a cross-sectional prevalence study of watermen working where Pfiesteria exposure may occur: waters where diseased or stressed fish were reported from June to September 1997, and where Pfiesteria had been identified in the past. Controls worked on unaffected waterways. The study was conducted 3 months after the last documented Pfiesteria-related fish kill. The goal was to document any persistent health effects from recent or remote contact with fish kills, fish with lesions, or affected waterways, using the 1997 U.S. Centers for Disease Control and Prevention case description for estuary-associated syndrome (EAS). Examinations included comprehensive medical, occupational, and environmental history, general medical, dermatologic, and neurologic examinations, vision testing, and neuropsychologic evaluations. Seventeen of 22 watermen working in affected waters and 11 of 21 in unaffected waters reported exposure to a fish kill or to fish with lesions. We found no pattern of abnormalities on medical, neurologic, neuropsychologic, or NES-2 evaluation. By history, one subject in each group met the EAS criteria, neither of whom had significant neuropsychological impairment when examined. Watermen from affected waterways had a significant reduction in visual contrast sensitivity (VCS) at the midspatial frequencies, but we did not identify a specific factor or exposure associated with this reduction. The cohorts did not differ in reported occupational exposure to solvents (qualitative) or to other neurotoxicants; however, exposure history was not sufficiently detailed to measure or control for solvent exposure. This small prevalence study in watermen, conducted 3 months after the last documented fish kill related to Pfiesteria, did not identify an increased risk of estuary-associated syndrome in those working on affected waterways. A significant difference between the estuary and ocean watermen was found on VCS, which could not be attributed to any specific factor or exposure. VCS may be affected by chemicals, drugs, alcohol, and several developmental and degenerative conditions; it has not been validated as being affected by known exposure to dinoflagellate secretions. VCS should be considered for inclusion in further studies, together with documentation or quantification of its potential confounders, to assess whether it has utility in relationship to dinoflagellate exposure.

Occupational exposure to inorganic mercury vapour and reproductive outcomes.

The effect of exposure to inorganic mercury on the pregnant woman and her foetus has received little attention. Transport of elemental inorganic mercury into foetal tissues has been reported, and prior studies indicate a higher incidence of adverse pregnancy outcome. The effects of occupational exposure to inorganic mercury on pregnancy were investigated among 46 exposed women workers: controls were 19 women working in non-production areas of the same factory. There were 104 recorded total pregnancies during the period 1948-77. The study revealed a higher frequency of adverse reproductive outcomes, especially congenital anomalies, among the women exposed to inorganic mercury levels at or substantially lower than 0.6 mg/m3; no significant differences in the stillbirth or miscarriage rates were noted between the two groups of women. The overall foetal death rate in this study was similar to New York state (USA) and national levels for the same period.

Potential for respirable quartz exposure from North Carolina farm soils.

Sandy-loam soils from six active farms in the coastal plains of North Carolina (USA) were analyzed for aerodynamic equivalent diameter and quartz content and compared with results to similar analyses of clay soils of the Piedmont and sandy soils from the sand hills of North Carolina to see whether respirable quartz content varies with soil type. The respirable fraction of sandy loam-soils averaged 0.04 (SD 0.02) versus 0.13 (SD 0.03) for clay soils and 0.04 (SD 0.03) for sandy soils. Quartz content in the 4.25 mu m fraction of sandy-loam soils averaged 15.2 (SD 4.1) % versus 2.2 (SD 0.8) % in clay soils and 29.0 (SD 11.1) % in sandy soils. The mass of respirable quartz in sandy-loam soils averaged 0.7 (SD 0.4)% versus 0.3 (SD 0.1)% in clay soils and 1.0 (SD 0.4) % in sandy soils. These results suggest that, during dusty farm activities, there is a potential for greater respirable quartz exposures associated with work with sandy or sandy-loam soils than from work with clay soils.

Teaching occupational and environmental medicine in primary care residency training programs: experience using three approaches during 1984-1991.

There is a critical shortage of physicians trained to recognize and treat occupational and environmental health problems. We implemented several required teaching programs for internal medicine and family medicine residents that focus on providing primary care for these problems. Clinical experiences were developed using the university and medical center as an example of a workplace with chemical and physical hazards. On-site experiences were also provided at local industries, but when resident stipend support for this aspect was discontinued, that part of the program was suspended. Didactic programs were associated with a statistically significant improvement in house staff knowledge scores. These occupational and environmental health issues can be introduced during residency, resulting in increased expertise in this discipline.

Irritant symptoms and immunologic responses to multiple chemicals: importance of clinical and immunologic correlations.

An evaluation of workers in a plant was conducted because of multiple complaints of ocular, nasal, skin and chest symptoms. Antibody activity against 4 different chemicals was identified: an aliphatic diisocyanate, 4-vinylcyclohexene dioxide, trimellitic anhydride (TMA) and an unknown chemical present in a plasticizing ester known as n-octyl-n-decyl-trimellitate. The source of TMA which resulted in immunization in the plant is unknown. The presence or absence of antibodies did not correlate with the presence or absence of symptoms and it was concluded that no occupational allergic disease was present in these workers. Antibody studies alone do not make a diagnosis of occupational allergic disease and clinical correlation is required. Immunoassays may be useful in identifying exposures to immunizing chemicals in the workplace for potential clinical correlation or for exposure monitoring in the workplace.

Adherence to explicit strategies for common medical conditions.

Explicit strategies (protocols) were prepared by the staff of a primary care clinic for use as professional standards by physicians, nurse practitioners and physicians' assistants to improve care and facilitate quality assessment in cases of urinary tract infection and upper respiratory illness. Over a 2-year period, audit of 3,442 records for adherence to protocol guidelines revealed a variation with time of 38 to 100 per cent in checklist utilization and 55 to 100 per cent in compliance with specified procedures. Shifting patterns of clinic load and alterations in feedback mechanisms to providers had little relation to guideline adherence. The range in scores was attributed to patient symptom variability with subsequent difficulty applying explicit strategies, and to failure of providers to record details contributing to clinical decisions. With this range of "success" following self-imposed predefined strategies, it is not surprising that retrospective record reviews using short sample periods and criteria established by outside expert panels document wide variation in quality.

Microenvironmental exposure to mercury vapor.

Work area and breathing zone samples were collected in a factory utilizing metallic mercury and analyzed for mercury vapor content. Breathing zone samples averaged several fold higher in concentration than concurrent area samples, reflecting a "microenvironmental" exposure to mercury vapor, presumably from contaminated clothing and hands. Blood and corrected total urine mercury values correlated well with the average microenvironmental exposure level for each worker. Measurements of unbound mercury in urine samples were sensitive at picking up minimal exposures. Excessive amounts of unbound mercury were not found in the urine, even with wide day-to-day swings in microenvironmental mercury vapor levels, suggesting that the human body can adapt to a chronic, moderate exposure to mercury vapor.

Methylmercury in the environment: a review of current understanding.

The danger of methylmercury poisoning appears to be slight when the environment is not directly contaminated with methylmercury. Sediments rapidly bind mercury and decrease its availability to aquatic organisms. Sediments further have a greater propensity to demethylate than to methylate mercury. In noncontaminated aquatic ecosystems, the concentrations of methylmercury and inorganic mercury are many times lower than those that have been found to cause toxicity, even in the most sensitive organisms. Methylmercury bound to protein is comparatively less toxic than methylmercury salts, and selenium present in this protein appear to be one of the major detoxifying agents for methylmercury. This is particularly important in seafood, where there is an excess of selenium compared to methylmercury.