Robert B. Reger

The prevalence of coal workers' pneumoconiosis in US coal miners.

The National lnstitute of Occupational Safety and Health of the US public Health Service recently completed the first round of a large field study to determine the prevalence of coal workers, pneumoconiosis in working US coal miners. Between October 1969 and July 1971 a total of 9,076 miners from 29 bituminous and 2 anthracite mines were examined. An overall prevalence of nearly 30% was found. However, progressive massive fibrosis occurred in only 2.5% of the sample. when the data were broken down according to the geographic region in which the mine is situated, marked regional differences in prevalence were apparent. Thus, while 45% of the Eastern Pennsylvania anthracite miners had simple pneumoconiosis and a further 14% had progressive massive fibrosis, the comparable figures for bituminous miners in Colorado were 4.6% and 0%. No obvious cause for these disparities in prevalence was apparent.

Ventilatory capacity and lung volumes of US coal miners

Lung volumes and ventilatory capacity of 9,076 coal miners were determined during the period 1969-1971. The data collected indicate that, while coal mining may in certain instances lead to very minor reductions of ventilatory capacity, such reductions are minimal in the absence of complicated pneumoconiosis and would not be associated with respiratory disability. (CIS Abstr.)

Chronic Respiratory Effects of Exposure to Diesel Emissions in Coal Mines

A 5-yr prospective design was employed to test the hypothesis that exposure to diesel emissions leads to chronic respiratory effects among underground coal miners. Changes in respiratory function and development of chronic respiratory symptoms were measured during a 5-yr study period (i.e., 1977 to 1982) in 280 diesel-exposed and 838 control miners from Eastern and Western United States underground coal mines. Spirometry measures of respiratory function included forced expiratory volume in 1 sec (FEV1.0), forced vital capacity (FVC), and forced expiratory flow rate at 50% of FVC (FEF50). Chronic respiratory symptom measures, which included chronic cough, chronic phlegm, and breathlessness, were obtained by questionnaires, as were smoking status and occupational history. Based upon these data, the pattern of evidence did not support the hypothesis either in an age-adjusted comparison of diesel vs. nondiesel miners or in an internal analysis by cumulative years of diesel exposure.

Determination of lung volumes from chest films

The results obtained from two radiological methods of determining total lung capacity (TLC) (Kovachs parabo oid and Barnhards ellipsoid) were compared with those obtained with the body plethysmograph. Determinations of TLC were made in four groups of subjects: group 1 consisted of 26 miners most of whom had simple pneumoconiosis; group 2 consisted of 12 normal subjects; group 3 consisted of eight subjects who had a variety of chest disease, but with no demonstrable parenchymal or pleural opacification; and group 4 consisted of 19 subjects with miscellaneous diseases, all showing demonstrable infiltration or opacification. The values obtained by the method of Kovach and his colleagues often differed markedly from the plethysmographic determinations, and it became apparent that this method was not sufficiently accurate. On the other hand, the technique of Barnhard and his colleagues gave results that were essentially similar to, and as far as we can say interchangeable with, those obtained by the body plethysmograph in groups 1, 2, and 3. In subjects with marked pulmonary opacification or infiltration, the disparity between Barnhards method and the plethysmograph tended to be more sizeable. It was concluded that Barnhards method for determining total lung capacity is accurate and could be applied to epidemiological surveys.

A COMPARISON OF THE PREVALENCE OF COAL WORKERS' PNEUMOCONIOSIS AND RESPIRATORY IMPAIRMENT IN PENNSYLVANIA BITUMINOUS AND ANTHRACITE MINERS

The opinion has often been expressed that anthracite miners are more prone to develop pneumoconiosis and respiratory disability than are their bituminous counterparts. Yet this belief is difficult to prove, and most previous studies in which the respiratory status of anthracite and bituminous miners have been compared have suffered either from faulty selection or poor participation. Thus, when Lieben and colleagues made their prevalence survey of pneumoconiosis in central Pennsylvania, they obtained only 25 % participation; in Eastern Pennsylvania, the same workers obtained a 60% response,? but even the latter can hardly be regarded as satisfactory. Comparison between groups such as these is fraught with danger. On the other hand, the United States Public Health Service and Bureau of Mines have recently started a long term study of the prevalence of progression of coal workers’ pneumoconiosis (CWP), and to date miner participation has been excellent. The data collected in this study permit valid comparison of the prevalence of CWP and the various respiratory impairments seen in Pennsylvania bituminous, as opposed to anthracite, miners.

Analysis of components of variation in a radiological method for determining total lung capacity.

An attempt was made to characterize quantitatively the several components of variation existing in the determination of total lung capacity (TLC) by a radiological method. An analysis of variance indicated that over 94% of the total variation could be attributed to film differences, the remaining 6% being a consequence of interobserver and intraobserver variation and the inherent random variability. It was shown that a relative error of about 5.8% could be expected with one observer making one determination for each set of films. An error of this magnitude compares favorably with other methods for determining TLC. It was, therefore, concluded that TLC determined by this method is repeatable and consequently can be used in large-scale epidemiological studies.