A follow-up study on the lung disorders of rush (igusa) farmers exposed to "sendo" dust.

In the process of "tatami" mat production, from cultivating to weaving, rush farmers are exposed to "sendo" (dyer's earth) dust using it to prevent fading of the "tatami" mat color. It has been found that the workers tend to develop a relatively early stage of pneumoconiosis after about 20 years of this work. In 1980, 51 male (58.6 years old) and 37 female (54.4 years old) rush farmers, some of whom were previously examined in 1970, were re-examined for lung disorders. Chest X rays in the 1980 showed, 49.0% of males and 62.2% of females over 1/0 according to the 12 point profusion scale with irregular small opacities being dominant, a significant increase in the prevalence rates of pneumoconiosis compared with 1970 values (p less than 0.01 for both males and females). A relatively high prevalence of respiratory complaints and/or lung function impairment was also found. However, there were no severe cases and no significant changes were seen to have occurred during the seventies by those tests. It was also observed that increases in lung disorders during the decade were more common in the female workers. These findings suggest that the pathogenesis of rush farmer's pneumoconiosis might be in the histological changes of bronchial and/or alveolar walls by the deposition of "sendo" dust. The present study revealed that the lung disorders in the rush farmers may be associated with long-term inhalation of "sendo" dust, and the introduction of more suitable dust control measures in that processing must be actively pursued in the near future.