Relationship between cumulative occupational exposure to asbestos fibres and respiratory symptoms

A survey of chronic respiratory symptoms was undertaken in 1127 asbestos workers engaged in asbestos mining, asbestos cement production, production of friction materials or in the manufacture of asbestos textile. A control group of 593 persons was also surveyed. The exposure of asbestos workers was analysed by evaluating separately the cumulative exposure to total airborne particles and to airborne asbestos fibres. The prevalences of all the respiratory symptoms (chronic cough, chronic phlegm, chronic bronchitis, dyspnoea grade 3+) were significantly higher in asbestos workers compared to controls in both nonsmokers and smokers (p less than 0.01). The prevalences of all the respiratory parameters in asbestos workers increased with both the length of employment and cumulative exposure to total airborne particles. Prevalences of chronic cough, chronic phlegm and chronic bronchitis did not show an increase with cumulative exposure to airborne asbestos fibres expressed as fibres/cc years. It is concluded that the development of chronic cough, chronic phlegm and chronic bronchitis in asbestos workers is likely to be an unspecific effect of the exposure to the difficulty soluble airborne particles rather than a specific effect of the exposure to airborne asbestos fibres.