A study of the importance of ‘total’ dust (as compared with the respirable fraction) in causing upper respiratory disease. Final report on CEC Contract 7246-16/8/003

The importance of the role of dust in the development of coalminers’ pneumoconiosis is well established but its relationship with upper respiratory disease (‘chronic bronchitis’) is less well defined. Research carried out within the last 10 years has demonstrated relationships between the prevalence of chronic respiratory symptoms, reduction of lung function and exposure to the mass of the so-called respirable fraction of coalmine dust. It has been suggested, however, that a fraction of the airborne dust which contained more larger particles than the respirable fraction might be more appropriate for comparison with upper respiratory disease. The aim of the present study is to examine this question.Environmental and medical data were available from the first 10-year period of the National Coal Board’s Pneumoconiosis Field Research. The basic dust measures were of size and particle number concentration parameters together with some direct measurements of respirable mass concentrations taken towards the end of this period. These were used to derive ‘total’ and respirable concentrations for various working occupations. The cumulative dust exposures of individual coalface workers were calculated from these data and the working time spent in the different occupations, taking account also of their working histories prior to the research. These exposures were examined in relation to fall in FEV 1.0 and the prevalence of cough and/or phlegm, recent chest illness and dyspnoea. In the analysis, account was taken of age, smoking habit and physique.Dust exposures based on ‘total’ volume and mass concentrations correlated more closely with declining FEV 1.0 and clinical symptoms of upper respiratory disease than did those obtained from exposures based on ‘total’ and respirable particle number concentrations. The use of ‘total’ volume and mass concentrations, however, gave correlations not significantly different from those obtained by the use of respirable mass concentration.The need for further work to examine the relationship between upper respiratory disease and more specific dust size fractions is considered. The rationale in relation to instrumentation, including personal samplers, with the requisite sampling characteristics, now currently being developed with help from the C.E.C., is discussed.