09:30 - 12:30, 3 hours, International Conference Hall
Plenary Session 4
Medical Aspects: Surveillance and Treatment of Asbestos-related Diseases
4-B: Diagnosis and Treatment of Asbestos-Related Diseases
Chairs: Bruce Robinsoni [not-confirmed] and Takashi Nakano
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Antti Tossavainen
Institute of Occupational Health (FIOH), Helsinki, Finland
ABSTRACT:
The International Expert meeting on Asbestos, Asbestosis and Cancer was convened in Helsinki on 20-22 January 1997 to discuss disorders of the lung and pleura and to agree contemporary criteria for their diagnosis and attribution with respect to asbestos. The group decided to name the consensus report as 'The Helsinki Criteria' (Scand J Work Environ Health 1997;23:311-316).
The clinical diagnosis of asbestos-related diseases is based on a detailed interview of the patient and occupational data on asbestos exposure, signs and symptoms, radiological and lung physiology findings, and selected cytological, histological and other laboratory studies. Asbestosis is generally associated with relatively high exposure levels. Radiological findings of small opacities (ILO grade 1/0) are usually regarded as early stage of asbestosis. Smoking effects should be considered in the evaluation of lung function tests and respiratory symptoms. A histological diagnosis of asbestosis requires the identification of diffuse interstitial fibrosis in well inflated lung tissue plus the presence of asbestos bodies or uncoated fibres. Low exposures from work-related, household and natural sources may induce pleural plaques but for diffuse pleural thickening, higher exposure levels may be required.
For mesothelioma, an occupational history of brief or low-level exposure should be considered sufficient. A lung fibre count above the background range, radiological findings or histopathological evidence can also relate a case of pleural or peritoneal mesothelioma to asbestos exposure. Smoking has no influence on the risk of mesothelioma.
All major histological types of lung cancer can be related to asbestos. Clinical signs and symptoms are of no significant value in deciding whether or not an individual case is attributable to asbestos. One year of heavy exposure (manufacture of asbestos products, asbestos spraying, insulation work, demolition of old buildings) or 5 - 10 years of moderate exposure (construction, shipbuilding) may increase the lung cancer risk 2-fold or more. A minimum lag-time of 10 years from the first exposure is required. A cumulative exposure of 25 fibre-years was estimated to double the risk of lung cancer. The presence of asbestosis is an indicator of heavy exposure and can contribute some additional risk of lung cancer beyond that conferred by asbestos exposure alone. A 2-fold risk of lung cancer is related to retained fibre levels of 2 million (>5 ƒÊm) or 5 million (>1 ƒÊm) amphibole fibres per gram dry lung tissue. This concentration is approximately equal to 5000 to 15000 asbestos bodies per gram dry tissue, or 5 to 15 asbestos bodies per millilitre of bronchoalveolar lavage fluid. Tobacco smoking does not detract from the risk of lung cancer attributable to asbestos exposure.