Long-term Effects of Sulphur Dioxide Exposure in Pulp Mills

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Abstract
This work is concerned with the problem of the chronic toxicity of sulphur dioxide in pulp mills. Fifty-four workers at four different pulp mills working in the acid towers and digester plants have been investigated with special regard to symptoms and signs of respiratory disease. Vital capacity has been measured with a `Kifa' apparatus and maximal expiratory flow with a Wright peak flow meter. The concentration of sulphur dioxide in the working atmosphere has been measured during general working conditions on a single day, and the values were found to range between 2 and 36 parts per million. The control group consisted of 56 paper industry workers from the same district with similar working conditions but working in an atmosphere free from objectionable gases. No significant difference in age or smoking habits was found between the groups. A significantly higher frequency of cough, expectoration, and dyspnoea on exertion was found in the exposed group, the difference being greatest in age groups under 50 years. The average maximal expiratory flow rate was significantly lower (P = 0·05) in the exposed group than in those not exposed for men under 50 years. Over this age there was no significant difference between the two groups. Vital capacity values showed no significant difference between the groups.