The adverse effects of asbestos were first observed in the early 1900s and the relation ship to mesothelioma was suggested in the 1940s. One of the earliest reports linking mesothelioma to occupational asbestos exposure came out of the medical clinic at an asbestos mine in Canada. At a scientific meeting in 1952 Cartier, then in charge of the industrial medical clinic at Thetford Mines, Quebec, reported eight cases of respiratory cancer, two of which he described as pleural tumors. He declared that two such rare cancers in a small series of only eight cases suggested an occupational origin. By 1960 the scientific community generally recognised asbestos as a cause of mesothelioma.
However, the issue was far from settled. In a national survey of mesothelioma in Canada from 1960 to 1968, McDonald a history of asbestos contact in a relatively small proportion of cases – mostly in insulation and allied trades rather than in the asbestos-producing industry. They surveyed pathologists across the country to find all cases of mesothelioma after 1959. They found 165 cases (111 pleural, 47 peritoneal, 3 both and 4 pericardial). Updates in subsequent years showed a slightly increased association with asbestos exposure, but still lower than expected.
When pathologists reviewed the cases12 the diagnosis was confirmed in only about 50 per cent of the cases, among whom the incidence of asbestos exposure was also higher.
A follow-up analysis added a chrysotile mining industry cohort and two small groups of employees in gas mask factories to the survey data. They found 254 fatal cases of mesothelioma (181 men, 73 women) in Quebec from 1960 to 1978.
They were able to obtain occupational and residential histories for the majority, and found that only about 40 per cent of the male cases and 5.4 per cent of the female cases were attribut-able to occupational asbestos exposure (asbestos manufacture, production, insulation, heating trades, shipyards, and construction). Six people probably had household expo-sure.
The intervals between first employment and death from mesothelioma were longer for miners and millers than for manufacturing workers. All the miners and millers had pleural mesothelioma, while the factory workers included 8 with peritoneal mesothelioma. The incidence did not clearly increase over this time period.
In 1994 Spirtas published a study aimed at defining the attributable risk of asbestos exposure in the United States. They used the Los Angeles County Cancer Surveillance Program, the New York State Cancer Registry (excluding New YorkCity), and 39 large Veterans Administration hospitals to identify people diagnosed with mesothelioma from 1975 to 1980. They identified 208 cases of pathologically confirmed mesothelioma. Controls were 533 people who had died of other causes.
They interviewed immediate family members to obtain asbestos exposure history. Among men the attributable risk for asbestos exposure was 88 per cent, among women it was 23 per cent (although the confidence interval was very wide at 3–72%). The increasing incidence of mesothelioma in the United States is primarily due to the increased incidence among
men, thus probably reflecting more occupational exposure.
Most patients with mesothelioma do have a history of exposure to asbestos, al- though it may have been brief and remote in time. The variability in percentages of cases with identifiable asbestos exposure may be related to several factors: incomplete history taking, unknown or hidden occupational exposures, or environmental exposure.
However, the issue was far from settled. In a national survey of mesothelioma in Canada from 1960 to 1968, McDonald a history of asbestos contact in a relatively small proportion of cases – mostly in insulation and allied trades rather than in the asbestos-producing industry. They surveyed pathologists across the country to find all cases of mesothelioma after 1959. They found 165 cases (111 pleural, 47 peritoneal, 3 both and 4 pericardial). Updates in subsequent years showed a slightly increased association with asbestos exposure, but still lower than expected.
When pathologists reviewed the cases12 the diagnosis was confirmed in only about 50 per cent of the cases, among whom the incidence of asbestos exposure was also higher.
A follow-up analysis added a chrysotile mining industry cohort and two small groups of employees in gas mask factories to the survey data. They found 254 fatal cases of mesothelioma (181 men, 73 women) in Quebec from 1960 to 1978.
They were able to obtain occupational and residential histories for the majority, and found that only about 40 per cent of the male cases and 5.4 per cent of the female cases were attribut-able to occupational asbestos exposure (asbestos manufacture, production, insulation, heating trades, shipyards, and construction). Six people probably had household expo-sure.
The intervals between first employment and death from mesothelioma were longer for miners and millers than for manufacturing workers. All the miners and millers had pleural mesothelioma, while the factory workers included 8 with peritoneal mesothelioma. The incidence did not clearly increase over this time period.
In 1994 Spirtas published a study aimed at defining the attributable risk of asbestos exposure in the United States. They used the Los Angeles County Cancer Surveillance Program, the New York State Cancer Registry (excluding New YorkCity), and 39 large Veterans Administration hospitals to identify people diagnosed with mesothelioma from 1975 to 1980. They identified 208 cases of pathologically confirmed mesothelioma. Controls were 533 people who had died of other causes.
They interviewed immediate family members to obtain asbestos exposure history. Among men the attributable risk for asbestos exposure was 88 per cent, among women it was 23 per cent (although the confidence interval was very wide at 3–72%). The increasing incidence of mesothelioma in the United States is primarily due to the increased incidence among
men, thus probably reflecting more occupational exposure.
Most patients with mesothelioma do have a history of exposure to asbestos, al- though it may have been brief and remote in time. The variability in percentages of cases with identifiable asbestos exposure may be related to several factors: incomplete history taking, unknown or hidden occupational exposures, or environmental exposure.
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