Asbestos diseases: Asbestosis
Asbestos is a silicon-containing mineral that began to be produced on a large scale around 1870, with the increase in the use of fire-retardant insulation materials. The beneficial properties of asbestos cement, also known as Eternit, were discovered around 1900. Asbestos use in the Netherlands increased sharply from 1930. At that time it became clear that asbestos can affect the health. The relationship between working in the asbestos industry and the formation of fibrous lungtissue, known as diffuse pulmonary fibrosis was demonstrated. A relationship to lung cancer was established after the second World War, and, in 1960, a link to malignant mesothelioma was established. Worries about the health effects of asbestos increased also in the Netherlands after 1970 and protective measures were progressively introduced in the asbestos processing industry. The publication of the Asbestos Decree followed in 1978. The storage and processing of asbestos were forbidden by law in the Netherlands in 1993.
Although everyone in the Netherlands has been exposed to asbestos, asbestos-related diseases are almost exclusively traceable to occupational exposure. The major asbestos-related diseases are malignant mesothelioma, asbestosis and lung cancer. The Health Council of the Netherlands has previously published an advisory report on malignant mesothelioma. The present advisory report is devoted to asbestosis.
Asbestosis is a chronic disease in which clearance reactions following inhalation of asbestos fibres stimulate diffuse inflammatory reactions and cell growth, which lead to the formation of fibrous tissue in the lungs. The formation of fibrous tissue results in a severe loss of elasticity and the lung loses its ability to take up oxygen. This eventually results in shortness of breath, disability and death. Approximately half the patients with asbestosis die from a form a lung cancer.
Asbestosis protocol
In this advisory report, the Committee recommends a protocol to establish occupational exposure related asbestosis.
The diagnosis is made in various stages, which involve successively demonstrating the formation of fibrous tissue in the lung, determining the degree to which the person affected has been exposed to asbestos occupationally, and how the disease could have developed as a result of this, and determining the severity of the impairment of the lung function caused by the formation of the fibrous tissue.
The first step is to ascertain the formation of fibrous tissue (diffuse pulmonary fibrosis) on morphological grounds, usually with the help of techniques used in X-ray diagnosis, such as the ’high-resolution computed tomography’ scan (HRCT). Where available, a biopsy can also be used to confirm pulmonary fibrosis. However, the Committee rejects requiring a biopsy specimen for this because it would involve unjustifiable surgical intervention for a patient with asbestosis.
Once fibrosis has been demonstrated, the relationship to asbestos in the lung should be demonstrated by means of an occupational case history. In the Netherlands, owing to the extreme scarcity of historical data about occupational exposure to asbestos, it is unrealistic to expect to obtain a completely quantitative estimate of previous exposure to asbestos. The Committee therefore believes it is satisfactory to establish qualitatively that the person concerned has been occupationally exposed to an amount of asbestos that exceeds the exposure threshold value considered necessary for developing asbestosis. This can be ascertained by estimating possible total exposure on the basis of an occupational case history compiled with the aid of available historical exposure data from the Netherlands and abroad for a number of significant industries and occupations, and determining whether this exceeds the exposure threshold value. The Committee concludes on the basis of epidemiological research data from abroad that the exposure threshold value corresponds with a minimum exposure of five fibre years. In addition, the sick person’s exposure to asbestos must have started at least fifteen years before the manifestation of the disease. The severity of the disease is classified according to the system of the European Respiratory Society.
If the occupational case history provides insufficient data and a biopsy or a bronchoalveolar lavage (BAL) is available, the conclusion that there is asbestosis can also be reached by establishing that the cause of the fibrosis lies in the presence of asbestos fibres or asbestos particles in the lung. If no biopsy is available, this can be achieved by assessing the result of a bronchoalveolar lavage. However, it must then have been established that the person concerned has worked in an occupation or industry in which exposure to asbestos could have occurred and that the work was started more than fifteen years before the manifestation of the disease.
Lung function disorders must be established using standard lung-physiological techniques in laboratories that regularly perform examinations of this kind and that are certificated to do so on qualitative grounds. The Committee recommends ensuring that these centres are regionally distributed.
Because an increase in a lung function disorder may also occur after a long period, the Council recommends providing the possibility of a re-evaluation of the lung function disorder after three years.