A Study on Pneumoconiosis due to Diatomaceous Earth Dust

(Report 2) Immunological examinations in workers with and without pneumoconiosis

Abstract

The purpose of this study was to define immunological changes in workers exposed to diatomaceous earth dust. Immunological tests were performed on 89 workers exposed to the dust and 40 healthy farmers who were used as a control group. Immunological tests included tuberculin skin tests (control subjects were excluded), CRP tests, RA tests, evaluations of serum protein concentration and its fractions, and serum immunoglobulin levels which are labelled IgG, IgA, IgM and IgD. All subjects were males ranging in age from 40 to 55 years.
Workers were divided into two groups; one group included 20 workers with pneumoconiosis and 69 workers without as had been diagnosed by chest roentgenographic examination.
The following results were obtained:
1. Significant differences were not observed in positive tuberculin skin test rates between workers with and without pneumoconiosis.
2. Positive rates for the CRP test of workers with pneumoconiosis was significantly higher than those of the other two groups.
3. Positive rates for the RA test did not show significant differences among the three groups.
4. For serum protein concentration evaluations and its fractions, mean values of β-globulin and γ-globulin were significantly higher and the A/G ratio was significantly lower among workers with pneumoconiosis than among the control group. The mean values of β-globulin for workers without pneumoconiosis were significantly higher than for those the control group. The mean value of γ-globulin was significantly higher and the A/G ratio was significantly lower for workers with pneumoconiosis than for those without it.
5. For serum immunoglobulin levels, the mean values of the IgG were not significantly different, the IgA were slightly higher, and the IgM were significantly higher for workers both with and without pneumoconiosis than the controls. The mean values of the IgD for workers with pneumoconiosis was lower than those for the other two groups.
6. There were no significant correlations between immunological parameters including serum protein concentrations, β-globulin, γ-globulin, A/G ratio, IgG, IgA, IgM and IgD, and V₂₅/ht as respiratory function parameters for both workers with and without pneumoconiosis.
These results demonstrated that some significant immunological changes appear in workers exposed to diatomaceous earth dust whether or not they are afflicted by pneumoconiosis. It should be noted that the pneumoconiosis, for those in this study afflicted with it was mild in all cases.