COAL-MINE DUST EXPOSURE AND SPIROMETRY IN EXPERIENCED MINERS

In a previous study of new coal miners from the National Study of Coal Workers' Pneumoconiosis (NSCWP), researchers examined changes in spir ometry values associated with coal mine dust exposure (Br J Ind Med 19 93;50:929-937). An unusual pattern of dust-related effects was observe d: initial sharp decrements in FVC and FEV(1) were followed by partial recovery. In the current study, similar methods were used to analyze data from experienced miners. Each of 1,915 male subjects contributed data from two of the NSCWP field surveys: either Round 1 (1969-71) or Round 2 (1972-75) and Round 4 (1985-88). From the cross-sectional anal ysis at Round 1 or Round 2 (R1/R2), changes of +0.6 ml FVC and -0.5 ml FEV(1) were associated with each mg/m(3)-yr of cumulative coal mine d ust exposure, but were not statistically significant (p > 0.05). From the analysis of longitudinal change in spirometry from R1/R2 to Round 4 (R4), annual declines in FVC (-0.10 ml/yr per mg/m(3)-yr, p = 0.003) and FEV(1) (-0.07 ml/yr per mg/m(3)-yr, p = 0.006) were associated wi th pre-R1/R2 exposure. Both the pattern and the magnitude of the expos ure-response relationship were different for experienced versus new mi ners. Possible reasons for these contrasts include differences in cumu lative exposure between the two groups and the healthy worker effect a mong experienced miners.