Henry W. Glindmeyer

Follow up study of workers exposed to man made mineral fibres.

A survey of workers in seven man made mineral fibre (MMMF) production plants, the subject of a previous report, was conducted, with other blue collar workers serving as regional comparisons. Based on the median reading of chest radiographs by five readers, a low prevalence of small opacities, all at the 1/0 and 1/1 profusion levels, was again found: for workers with MMMFs, 23/1435 (1.6%); for comparison workers, 2/305 (0.7%). Spirometric measurements indicated generally healthy populations, and were not related to presence of opacities. Ninety three per cent (21/23) of MMMF workers with opacities worked at the two plants with the highest exposures to fine fibres, resulting in a dose-response relation across plants. For one location, the prevalences of opacities for the MMMF and comparison workers were not significantly different (5.9% (13/220) v 3.1% (2/65)). No comparison x ray films were obtained for the MMMF plant with the highest prevalence (6.6%), so a second phase of the study was conducted, with pre-employment films from these two plants. On this second reading, the prevalence of opacities was lower; there were no significant differences between the two groups of films, and no relation between opacities and exposure indices. There was considerable inter and intrareader variability. These results indicate no adverse clinical, functional or radiographic signs of effects of exposure to MMMFs in these workers.

Limits of longitudinal decline for the interpretation of annual changes in FEV1 in individuals

Objective: Spirometry-based screening programmes often conduct annual assessment of longitudinal changes in forced expiratory volume in 1 second (FEV1) to identify individuals with excessive rates of decline. Both the American Thoracic Society (ATS) and the American College of Occupational and Environmental Medicine (ACOEM) recommend a reference limit value of ⩾15% for excessive annual decline. Neither the ATS nor the ACOEM adjust this limit for the precision of the existing spirometry data. The authors propose an improved method of defining the reference limit of longitudinal annual FEV1 decline (LLD) based on the precision of the spirometry data. Method: The authors used data from four monitoring programmes and measured their data precision using a pair-wise within-person variation statistic. They then derived programme- and gender-specific absolute and relative LLD values and validated these against the 95th percentiles for observed yearly changes in FEV1. Results: The relative limit for annual decline was more practical than the absolute limit as it adjusted for gender differences in the magnitude of FEV1. The programme-specific relative limit values were in good agreement with 95th percentiles for year-to-year FEV1 changes and ranged from 6.6% to 15.8%. For individuals with COPD and bronchial hyperreactivity the 95th percentiles for year-to-year changes were about 15% and higher. Conclusions: The relative longitudinal limit for annual FEV1 decline based upon precision of measurements is valid and can be generalised to different gender and population groups. A relative limit of approximately 10% appears appropriate for good quality workplace monitoring programmes, whereas a limit of about 15% appears appropriate for clinical evaluation of individuals with an obstructive airway disease. Computer software based on the method described is available from the corresponding author.

Interaction of atopy and exposure to cotton dust in the bronchoconstrictor response.

A survey of 255 workers in four cottonseed crushing mills included a respiratory health questionnaire, allergy skin testing, and measurements of lung function over the Monday working shift. Atopy was defined as having two or more positive weal reactions to common inhalant antigens. Categories of exposure to dust were based on the stage of milling, and one category contained workers with continuous exposure to cotton dust derived from linters, the cotton fibres adherent to cottonseed. Atopy and exposure to dust were found to have significant interaction: large mean declines in FEV1 and FEF 25-75 occurred only in the workers exposed to linter dust who were also atopic. Skin-testing surveys in cotton textile mills have concentrated on specific cotton antigen reactivity and its first-order relations to symptoms. Our results indicate a need to identify atopic workers, and to search for interactions between atopy and other variables that may influence acute changes in expiratory flow rates.

Progression of asbestos effects: a prospective longitudinal study of chest radiographs and lung function

From an original prospective cohort of 244 current and ex-workers in two asbestos cement plants, longitudinal radiographic data covering ten years were available for 165 and lung function data covering about six years for 150. Estimates of average and cumulative dust exposure were available for each participant, all men. Radiographic progression (onset or worsening) was assessed by comparing earliest and latest films side by side. Annual changes in lung function were computed by fitting regression lines to all the data points. Small opacities (ILO category 1/0 or higher) were found in 16% of initial films, and progression of small opacities occurred in 13% of film pairs. Average and cumulative dust exposure were each significant determinants of the initial presence of small opacities, and were determinants of the progression of both parenchymal and pleural abnormalities. There was greater likelihood of progression if an abnormality was initially present, and a greater likelihood of progression in the plant that had systematic use of some crocidolite. Initial levels of lung function were related to smoking, exposure to dust, and initial radiographic status. Mean annual declines in lung function were modest (FVC-0.017 l/y, FEV1-0.020 l/y) and were related to smoking but not exposure to dust, initial radiographic status, or radiographic progression. Both plants used mainly chrysotile asbestos and exposure levels declined severalfold after 1960. Our findings suggest a waning effect of the larger remote dust exposures on recent annual change in lung function. This accords with human and experimental pathology data showing the relatively low resistance of chrysotile fibres to chemical alteration and clearance.

Longitudinal limits of normal decline in lung function in an individual.

Objectives: The objectives of this study were to propose a method of calculating longitudinal limits of normal decline (LND) in forced expiratory volume in 1 second to identify individuals with an excessive decline in lung function and to compare the method with other published LND methods. Methods: We used longitudinal data from 11 workplace-based spirometric monitoring programs conducted from 1987 to 2001 on 12,729 workers to evaluate effectiveness of each LND method in identifying a “true” excessive decline in forced expiratory volume in 1 second defined using two criteria: slope >60 mL/year or >90 mL/year estimated over 5 or more years of follow up. Results: In comparison to the LND proposed by the American College of Occupational and Environmental Medicine, the proposed method had 5.0 to 2.7 times higher sensitivity over years 1 through 5 for the >60-mL/yr criterion. Conclusions: The proposed LND method was more effective than the other methods for identifying excessive declines.

Contributing factors to sandblasters' silicosis: inadequate respiratory protection equipment and standards

National concordance standards for respiratory protection during abrasive blasting have existed for more than 50 years; however, these standards have not kept pace with advances in blast equipment, have not provided realistic estimates of expected protection in the workplace, and have been misused by manufacturers and distributors of respiratory protective equipment who have assured, through sales literature, that the equipment is acceptable for conditions under which they have never been tested. This situation has contributed to exposure of sandblasters to hazardous levels of respirable free silica, and is reviewed here to prevent a continuation of the incompatibility of these and other standards for respiratory protection with the actual exposures to various noxious inhalants in the workplace.

A Survey of Size-Fractionated Dust Levels in the U.S. Wood Processing Industry

A survey of size-fractionated dust exposure was carried out in 10 wood processing plants across the United States as part of a 5-year longitudinal respiratory health study. The facilities included a sawmill, plywood assembly plants, secondary wood milling operations, and factories producing finished wood products such as wood furniture and cabinets. Size-fractionated dust exposures were determined using the RespiCon Personal Particle Sampler. There were 2430 valid sets of respirable, thoracic, and inhalable dust samples collected. Overall, geometric mean (geometric standard deviation) exposure levels were found to be 1.44 (2.67), 0.35 (2.65), and 0.18 (2.54) mg/m, for the inhalable, thoracic, and respirable fractions, respectively. Averaged across all samples, the respirable fraction accounted for 16.7% of the inhalable dust mass, whereas the corresponding figure for thoracic fraction as a percentage of the inhalable fraction was 28.7%. Exposures in the furniture manufacturing plants were significantly higher than those in sawmill and plywood assembly plants, wood milling plants, and cabinet manufacturing plants, whereas the sawmill and plywood assembly plants exhibited significantly lower dust levels than the other industry segments. Among work activities, cleaning with compressed air and sanding processes produced the highest size-fractionated dust exposures, whereas forklift drivers demonstrated the lowest respirable and inhalable dust fractions and shipping processes produced the lowest thoracic dust fraction. Other common work activities such as sawing, milling, and clamping exhibited intermediate exposure levels, but there were significant differences in relative ranking of these across the various industry segments. Processing of hardwood and mixed woods generally were associated with higher exposures than were softwood and plywood, although these results were confounded with industry segment also.

On-filter determination of collected wood dust by diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS)

A new analytical technique based on DRIFTS spectroscopy has been developed for the specific and sensitive determination of size-fractionated wood dust from 37 mm glass fiber filter samples collected with the Respicon sampler. A translational diffuse reflectance apparatus was modified to accept filter samples by incorporating a special filter holder in the sample stage and a clockwork motor to drive the translational stage during infrared scanning, thus providing an average analysis across the filter face. Filter samples were pre-treated with ethyl acetate to uniformly redeposit dust onto the filter and extract potential chemical interferences. Two absorbance maxima (1251 and 1291 cm(-1)), corresponding to the cellulose content of the wood, were suitable for quantitation of wood dust. Analysis of seven species of wood at 1291 cm(-1) showed an equivalent quantitative response for all species except maple. The response at 1251 cm(-1) was more variable across species but more sensitive for the softwoods. There was a statistically significant effect of particle size on the analytical response, so that analytical standards should be matched to the samples in terms of particle size distribution. Analytical limit of detection was approximately 0.08 mg of wood dust per sample with overall precision of about 6%. Comparison of DRIFTS and gravimetric analyses of 51 pure wood dust samples ranging from about 0.2 to 2 mg yielded a slope of 1.08 and r2 equal to 0.9. Other particulate contaminants common in the industrial wood processing industry showed little or no interference with the determination of wood dust by this method.