Pleural mesothelioma in Sweden: an analysis of the incidence according to the use of asbestos

Our plain-English summary of Pleural mesothelioma in Sweden: an analysis of the incidence according to the use of asbestos, by B. Järvholm, A. Englund, M. Albin (Occupational and Environmental Medicine, 1999).

The study

• Authors: B. Järvholm, A. Englund, M. Albin
• Journal: Occupational and Environmental Medicine
• Published: 1999;56(2):110-3
• Cited by: 64 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: To investigate if the preventive measures taken to reduce the occupational exposure to asbestos have resulted in a decreased incidence of pleural mesothelioma in Sweden.

Methods: The incidence of pleural mesothelioma between 1958 and 1995 for birth cohorts born between 1885 and 1964 was investigated. The cases of pleural mesothelioma were identified through the Swedish Cancer Register.

Results: In 1995, around 80 cases of pleural mesothelioma could be attributed to occupational exposure to asbestos. There is an increasing incidence in more recent birth cohorts in men. The incidence was considerably higher in the male cohort born between 1935 and 1944 than in men born earlier.

Conclusions: The annual incidence of pleural mesothelioma attributable to occupational exposure to asbestos is today larger than all fatal occupational accidents in Sweden. The first asbestos regulation was adopted in 1964 and in the mid 1970s imports of raw asbestos decreased drastically. Yet there is no obvious indication that the preventive measures have decreased the risk of pleural mesothelioma. The long latency indicates that the effects of preventive measures in the 1970s could first be evaluated around 2005.

In plain English

This study used Sweden's national cancer register to ask whether efforts to cut workplace asbestos exposure had lowered rates of pleural mesothelioma, a cancer of the lung lining. The authors counted cases recorded from 1958 to 1995 by sex, age and birth year, for people born 1885 to 1964. They compared these trends with Sweden's asbestos imports and rules. In 1995 there were 92 cases in men and 15 in women. Rates rose in more recently born men; in women the authors found at most a much weaker cohort trend. People born in the 1940s, who started work in the 1960s, when the first rule came in, showed no sign of lower risk. Subtracting the women's count from the men's, the authors estimated that 70 to 80 of the 1995 cases were caused by work exposure. That year there were 61 fatal work accidents. People born from 1955 on showed a first hint of lower risk, though cases were few. The authors said follow-up was too short to judge the 1970s measures; this could first be done around 2005.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: National register-based analysis of pleural mesothelioma incidence trends by sex, age and birth cohort, set against the history of asbestos use and regulation in Sweden
• Who was studied: All cases in the Swedish Cancer Register coded as pleural tumours with a histological diagnosis of mesothelioma, 1958 to 1995, in birth cohorts born 1885 to 1964. Only incidence below age 79 was included.
• Exposure: Occupational asbestos exposure, assessed only at the national level through asbestos imports and regulations. These included the first regulation in 1964, the first exposure limit of 2 fibres/ml in 1975, a ban on crocidolite in 1975, and a general prohibition in 1982 with some exceptions. A common estimate cited by the authors is that at least 90% of asbestos used in Sweden was chrysotile. There were no data on the individual cases' exposure.
• Main results:
  • In 1995 there were 92 cases of pleural mesothelioma in men and 15 in women, 107 in total. Taking the difference between men and women, the authors estimated that 70 to 80 cases were caused by occupational exposure to asbestos.
  • In the same year, 1995, there were 61 fatal occupational accidents in Sweden.
  • Incidence increased in more recent birth cohorts in men. The Results section reported no such tendency in women.
  • The Discussion stated that there is also a cohort trend among women, at a much lower level than in men.
  • For men aged 20 to 49, the crude incidences in the cohorts born 1930–4, 1935–9 and 1940–4 were 0.2, 0.6 and 0.7 cases/1000 person-years (as printed), highest in the latest cohort.
  • Among men aged 35 to 39, there was one case in the cohort born 1950–4, compared with a peak of seven cases in the cohort born 1940–4 (p less than 0.01, binomial distribution). Women had zero to one case.
  • People born during the 1940s started their working careers during the 1960s, and there was no indication that they had a decreased risk.
  • The authors suggested the 1960s regulations may have been insufficient to protect workers.
  • People born from 1955 onwards, who worked only under the stricter rules of the mid-1970s, had few cases. There was a first indication that they may have a decreased risk compared with earlier cohorts.
• The authors' conclusion: The authors concluded that the annual number of pleural mesotheliomas attributable to occupational asbestos exposure exceeded all fatal occupational accidents in Sweden. They found no obvious indication yet that the preventive measures had decreased risk. Because of the long latency, they said the effects of the 1970s measures could first be evaluated around 2005, and they considered that reducing asbestos exposure should have high priority.
• Limitations the authors state:
  • Follow-up was too short to show whether the 1970s regulations will prevent occupational mesothelioma.
  • There was no information on the type of asbestos the cases were exposed to, such as crocidolite or amosite.
  • Changes in diagnostic procedures may have contributed to the rising trend, at least during the 1960s. The authors argued this was not a major cause of the rise in men.
  • Below age 35, incidence was too low for trend analysis. The cohorts born from 1955 had not yet reached sufficient latency time.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Occupational Exposure, Latency.

Related studies

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• Incidence and familial risk of pleural mesothelioma in Sweden: a national cohort study — J. Ji, J. Sundquist, et al. (2016)
• Explaining differences in incidence rates of pleural mesothelioma between Sweden and the Netherlands — A. Burdorf, B. Järvholm, et al. (2005)
• Incidence, mortality and survival in malignant pleural mesothelioma before and after asbestos in Denmark, Finland, Norway and Sweden — K. Hemminki, A. Försti, et al. (2021)
• Estimation of the incidence of pleural mesothelioma according to death certificates in France — Y. Iwatsubo, M. Matrat, et al. (2002)
• Occupation and mesothelioma in Sweden: updated incidence in men and women in the 27 years after the asbestos ban — N. Plato, J.I. Martinsen, et al. (2016)

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