Woodhall Stopford

Riot Control Agents

This article is a revision of the previous edition article by Harry Salem, Bryan Ballantyne, and Sidney A. Katz, volume 3, pp 706–723,

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 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), 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.

Respirable Quartz Content of Farm Soils

Abstract We analyzed soils from 14 active farms in the piedmont and coastal plain regions of North Carolina for aerodynamic equivalent diameter (AED) and quartz content to see whether or not respirable quartz in tilled soils was in such quantities as to be a potential health hazard. The respirable fraction (that portion with an AED of 4.25 μm or less) of the clay soils ranged from 0.08 to 0.18 (mean of 0.13), while that of the sandy soils ranged from 0.01 to 0.09 (mean of 0.04). Quartz levels in the respirable fraction of sandy soils (29.0 ± 11.1%) were consistently higher than in clay soils (2.17 ± 0.85%). Likewise, the mass of respirable quartz particles made up a greater portion of sandy soils (1.02 ± 0.39%) than clay soils (0.29 ± 0.15%). Reports of silicosis and dust-related lung disease among farmers and workers handling crops from sandy soils suggest that there may be a hazard associated with exposure to respirable quartz found in soil. Stopford, C.M.; Stopford, W.: Respirable Quartz Content of Far...

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.

Carbonate fusion to determine quartz in respirable and bulk earth samples

Abstract The carbonate-fusion technique of Dobreva [Ann. Occup. Hyg., 18 (175) 121] has been modified to allow the colorimetric assay of solubilized quartz to be done entirely within a 4-ml disposable spectrophotometer cell. An Andreasen Pipette is used to measure respirable size of a sample (that with an aerodynamic diameter less than 3.5 μm) and to obtain samples at the 3.5 μm cut for quartz determinations. Amorphous silica and silicates are removed from the sample by heating an aliquot with 1−2 ml of 48% fluoroboric acid at 70°C for 1 h. Quartz is then preferentially solubilized by fusing the filtered and ashed residue with a 1:1 mixture of potassium bicarbonate and potassium chloride. After dissolving the carbonate residue with boiling water, a sample is placed in a polymethacrylate spectrophotometer cell with 0.1 ml of 10% ammonium molybdate. This mixture is then adjusted to pH 2.1 and kept at room temperature for 30 min. Color is then developed for 45 min with a solution of citric acid and tartaric acid after which absorbance is measured at 785 nm. This technique recovers 99.8% of 5 μm quartz but retains only 1.1% of amorphous silica. The absolute detection limit of the colorimetric method is 150 ng for silicon, sufficent to detect 8 μg of quartz in a 1−50 mg sample. Analyses of respirable-sized samples disclose that the major mass of quartz in complex earths can fall in the non-respirable range.