Longitudinal study of the FEV1, cumulative exposure to dusts and silicosis in gold miners

OBJECTIVES

The aim of this longitudinal study was to assess the rate of decline in FEV1 (deltaFEV1) in gold miners with silicosis and to relate these findings with the radiographic picture, age, smoking habits and cumulative exposure to dusts.

METHODS

The study included 73 gold miners with silicosis and 73 miners exposed to dusts but without silicosis. The clinical, radiological and functional assessment was made at least twice in each miner at the beginning and at the end of an adequate interval of the investigation which was extended for a mean period of 38.9 months for the group with silicosis and 33.6 months for the group without silicosis.

RESULTS

In the group of miners with silicosis deltaFEV1 was much higher (187 ml/year) as compared with the mean value found in the miners without silicosis (43.2 ml/year). No significant differences were found for deltaFEV1 according to the age criterion (in both groups) and to their smoking habits (in the group with silicosis). In silicosis, a very good correlation exists between the index of cumulative exposure to dusts and the magnitude of the decline rate of FEV1. In the miners, group without silicosis, deltaFEV1 had not any significant correlation with cumulative exposure to dusts.

CONCLUSIONS

Our observations revealed that the cumulative exposure to dusts affected the decline rate of FEV1 only to the extent to which it determined silicosis and intervened less in the functional decline in miners without silicosis. Smoking habits increased AFEV1 only in miners without silicosis.

Association between bronchial hyper-reactivity and exposure to silicon carbide

A clinical study of 191 workers in the silicon carbide production industry was carried out in order to determine the prevalence of respiratory symptoms (wheezing, dyspnoea and breathlessness after exercise). Such symptoms occurred in 50 (26.1%) subjects, of whom 24 accepted testing for bronchial reactivity. Of these 24, 19 (79.2%) were positive. These findings suggest that exposure to SiC may be associated with bronchial hyper-reactivity. Positive results were more frequent in women than in men, while differences between smokers and non-smokers were insignificant, a phenomenon that has often been noted in persons exposed to massive risk.

[Radiological observations in relation to occupational exposure to silicon carbide (SiC)]

There have been investigated radiologically 191 workers from a SiC factory, exposed to dust concentrations exceeding largely that TLV and with a content of non-reactive SiO2 less than 1%. Radiological examinations were performed systematically at a three years interval, beginning with 1988. Radiology interpreting was performed according to ILO 1980 classification for persistent radiological opacities due to mineral dusts. Our results sustain the idea of the pneumoconiogen potential of SiC: there is a high prevalence of radiological findings (16.2%) and the opacities have an extend from 2 to 6 areas and the profusion from 0/1 to 2/2.