[Chronic effect on the respiratory function of flax dust exposure].

One hundred workers of a flax factory were examined after a period of two years to study the behavior of the various indices of respiratory function. The drops per year in FVC and FEV(1.0) of 71 ml and 68 ml, respectively, were higher than expected in normal subjects not exposed to respiratory risk. The decreases in maximum expiratory flow (0.25 l/sec for Vmax 50% and 0.20 l/sec for Vmax 25%) are also higher than expected. No significant differences were observed between smokers and non-smokers, nor was any relationship with length of exposure found. For FVC and FEV(1.0) only there was a greater drop per year with increase in age, which can be explained as being a consequence of the latency necessary for development of airways disease. The greatest source of chronic risk is in the process immediately before spinning, where there is a great incidence of subjects with symptoms of chronic bronchitis and/or byssinosis, who show the maximum drop per year in the indices (FVC=-164 ml; FEV1=143 ml; Vmax 50%=-0.51 l/sec; Vmax 25%=0.30 l/sec). In the subjects most susceptible to dust, that is, those suffering from acute effects on mondays, the drop per year is midway between those of the symptomatic subjects and those of the non-symptomatic subjects. The forced expiratory curves showed good reproducibility, both when registered as volume/time and as flow/volume; there are no substantial differences in behavior between FEV1 and Vmax 50%.