Bjørn Gylseth

Fiber concentration in lung tissue of patients with malignant mesothelioma a case—control study

The risk of malignant mesothelioma associated with low‐level asbestos exposure is an important unresolved issue today. We have analyzed the asbestos fiber concentration in lung tissue from 14 cases of malignant mesothelioma and 28 case‐matched controls by scanning electron microscopy. The cases represent 86% of all mesotheliomas recorded by the Cancer Registry of Norway from the county of Hordaland between 1970 and 1979. Based on 1 million fibers per g of dried tissue as an indicator of cumulated asbestos exposure, the odds ratio (relative risk) was 8.5 (95% confidence limits, 2.3—31.1). Assuming that the risk of malignant mesothelioma is related to mineral fiber concentration in lung tissue, it is concluded that a fiber concentration exceeding 1 million fibers per g of dried tissue is associated with an increased risk of malignant mesothelioma. Furthermore, the results are consistent with a no‐threshold response.

SUBACUTE INHALATION TOXICITY OF MINERAL OILS, C15-C20 ALKYLBENZENES, AND POLYBUTENE IN MALE RATS

Male Wistar rats were exposed to mist and vapor of two mineral oils, two C15-C20 alkylbenzenes, and one polybutene at aerosol concentrations of 70 mg.m-3 and 700 mg.m-3 for 2 weeks. Of oil mist particles, 82-97 wt% were respirable (less than 4.7 microns). High-level exposure to polybutene was lethal to three of four animals, due to pulmonary edema. Elevated numbers of pulmonary macrophages and increased macrophage vacuolization were observed after exposure to the polybutene, both mineral oils, and one alkylbenzene. The same alkylbenzene produced body weight loss. Deposition analysis was performed for one mineral oil. No oil was detected in brain tissue, while retroperitoneal fat tissue contained 541 (401-702) micrograms oil/g tissue, half of this still present after an exposure-free period of 2 weeks. It is concluded that inhalation of the polybutene and one of the mineral cable oils tested here produces toxic effects in lung.

Medico-legal Aspects of Malignant Mesothelioma

The object of this investigation was to discuss medico-legal aspects of malignant mesothelioma in relation to social insurance legislation for occupational injuries and diseases in Norway. During the period 1960–79 the Cancer Registry of Norway recorded a total of 155 men and 35 women with malignant mesothelioma. However, only 21 men and no women were notified to the National Insurance Institution as occupational disease cases before 31 December 1979, in spite of the well established causal association between occupational asbestos exposure and the disease. The investigation is based on these 21 patients. The long latency period from first asbestos exposure until appearance of the disease and the short survival were evident in this study. Furthermore, the legislation and provisions for occupational injuries and diseases in Norway are obviously intended for occupational accidents, and consequently the legal assessment of patients with malignant mesothelioma was complicated. For those notified, the delay in notification was considerable, and only 50% were notified before death. Delay in the claim procedure was also substantial, and few patients survived the claim procedure period. The decisions were not consistent, particularly decisions regarding “the year of injury” and appeared to have been more restrictive during recent years. One of the 21 cases was not accepted as occupational disease, because domestic exposure was considered more probable than occupational exposure.