Cancer Incidence and Risk of Multiple Cancers after Environmental Asbestos Exposure in Childhood-A Long-Term Register-Based Cohort Study

Our plain-English summary of Cancer Incidence and Risk of Multiple Cancers after Environmental Asbestos Exposure in Childhood-A Long-Term Register-Based Cohort Study, by S.B. Dalsgaard, E.T. Würtz, J. Hansen, et al (International Journal of Environmental Research and Public Health, 2021).

The study

• Authors: S.B. Dalsgaard, E.T. Würtz, J. Hansen, O.D. Røe, Ø. Omland
• Journal: International Journal of Environmental Research and Public Health
• Published: 2021;19(1)
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: To examine the asbestos-associated cancer incidence and the risk of multiple cancers in former school children exposed to environmental asbestos in childhood.

Methods: A cohort of 12,111 former school children, born 1940-1970, was established using 7th grade school records from four schools located at a distance of 100-750 m in the prevailing wind direction from a large asbestos-cement plant that operated from 1928 to 1984 in Aalborg, Denmark. Using the unique Danish personal identification number, we linked information on employments, relatives' employments, date of cancer diagnosis, and type of cancer and vital status to data on cohortees extracted from the Supplementary Pension Fund Register (employment history), the Danish Cancer Registry, and the Danish Civil Registration System. We calculated standardized incidence rates (SIRs) for asbestos-associated cancers, all cancers, and multiple cancers using rates for a gender and five-year frequency-matched reference cohort.

Results: The overall incidence of cancer was modestly increased for the school cohort (SIR 1.07, 95% confidence interval (CI) 1.02-1.12) compared with the reference cohort. This excess was driven primarily by a significantly increased SIR for malignant mesothelioma (SIR 8.77, 95% CI 6.38-12.05). Former school children who had combined childhood environmental and subsequent occupational exposure to asbestos had a significantly increased risk of lung cancer. Within this group, those with additional household exposure by a relative had a significantly increased SIR for cancer of the pharynx (SIR 4.24, 95% CI 1.59-11.29). We found no significant difference in the number of subjects diagnosed with multiple cancers between the two cohorts.

Conclusions: Our study confirms the strong association between environmental asbestos exposure and malignant mesothelioma and suggests that environmental asbestos exposure in childhood may increase the overall cancer risk later in life.

In plain English

This Danish register-based cohort study followed 12,111 people born 1940–1970 who attended seventh grade at four schools 100–750 m downwind of a large asbestos-cement plant in Aalborg. They were compared with a reference cohort of 108,987 people matched on sex and age. Cancer follow-up ran from 1968 to the end of 2015. In the school cohort, 1,827 people developed at least one primary cancer other than non-melanoma skin cancer, more than expected (SIR 1.07, 95% CI 1.02–1.12). Malignant mesothelioma showed the largest excess: 38 cases against 4.33 expected (SIR 8.77, 95% CI 6.38–12.05). Among those with no known work or household exposure, the mesothelioma SIR was 5.09 (95% CI 2.82–9.20). Lung cancer was significantly raised only in those also exposed at work (SIR 1.34, 95% CI 1.05–1.72). Pharynx cancer was raised in those with both work and household exposure (4 cases; SIR 4.24, 95% CI 1.59–11.29). Multiple cancers were not significantly more common. The registers held no smoking or alcohol data, apart from smoking status for some lung cancer cases. The authors concluded that childhood environmental exposure may increase overall cancer risk later in life.

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: Register-based cohort study comparing a school cohort with a sex- and five-year-age frequency-matched reference cohort (1:9), using standardized incidence ratios
• Who was studied: 12,111 former pupils (6,087 male, 6,024 female) born 1940–1970 who attended one of four schools near the asbestos-cement plant in Aalborg, Denmark. They were followed for cancer from 1968 (or the start of seventh grade) to 31 December 2015. The reference cohort was 108,987 people sampled from the Danish Civil Registration System.
• Exposure: Environmental asbestos exposure in childhood from attending school and living 100–750 m in the prevailing wind direction from the Dansk Eternit asbestos-cement plant. The article cites an earlier source stating the plant used about 620,000 tons of asbestos, 89% of it chrysotile. Additional occupational exposure was estimated from employment records with a job-exposure matrix. Household exposure was counted when a relative was assessed as occupationally exposed.
• Main results:
  • All cancers excluding non-melanoma skin cancer in the school cohort: 1,827 observed versus 1,706.82 expected, SIR 1.07 (95% CI 1.02–1.12)
  • Malignant mesothelioma in the school cohort: 38 observed versus 4.33 expected
  • Malignant mesothelioma in the school cohort: SIR 8.77 (95% CI 6.38–12.05), the highest of the asbestos-associated cancers
  • Malignant mesothelioma among school cohort members exposed only to environmental asbestos (11 cases): SIR 5.09 (95% CI 2.82–9.20)
  • All asbestos-associated cancers in the school cohort: SIR 1.14 (95% CI 1.05–1.24). With mesothelioma excluded, the result was not statistically significant: SIR 1.07 (95% CI 0.99–1.17).
  • Apart from mesothelioma, no individual asbestos-associated cancer was significantly raised in the whole school cohort. Excesses that did not reach significance were seen for colon, larynx, lung, pharynx and stomach cancer.
  • Lung cancer in school cohort members also exposed to occupational asbestos (62 cases): SIR 1.34 (95% CI 1.05–1.72)
  • Pharynx cancer in school cohort members with both occupational and household asbestos exposure (4 cases): SIR 4.24 (95% CI 1.59–11.29)
  • Ovarian cancer was significantly lower in the school cohort (SIR 0.71, 95% CI 0.50–0.99). The authors stated that this points to no protective effect, because significance disappeared in the exposure subgroups.
  • Multiple cancers (more than one cancer) in the school cohort: 155 observed versus 143.74 expected, SIR 1.08 (95% CI 0.92–1.26), not significantly different from the reference cohort
  • All lung cancer cases from both cohorts with Danish Lung Cancer Registry data (163 in the school cohort, 2,802 in the reference cohort) were registered as current or former smokers
• The authors' conclusion: The authors concluded that their results confirm the strong association between environmental asbestos exposure and malignant mesothelioma. They also concluded that environmental asbestos exposure in childhood, not only occupational exposure, may have harmful effects on cancer risk.
• Limitations the authors state:
  • Possible confounders such as smoking, alcohol and other lifestyle factors were not in the registry data
  • Because co-carcinogens and confounders were missing, risk estimates for asbestos might be higher than the true estimates
  • Assessing occupational and household exposure through a job-exposure matrix may cause misclassification that could pull results toward no effect
  • Lack of detailed tobacco data prevented a firm conclusion on the role of smoking in the raised lung cancer risk
  • The small number of mesothelioma cases in the household and occupational-plus-household subgroups could explain the wide confidence intervals

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Cohort Study, Asbestos-Cement, Cancer Registry, Incidence, confidence interval, Malignant Mesothelioma, Occupational Exposure.

Related studies

• A Cohort Study on Cancer Incidence among Women Exposed to Environmental Asbestos in Childhood with a Focus on Female Cancers, including Breast Cancer — S.B. Dalsgaard, E.T. Würtz, et al. (2022)
• Letter Concerning: Glynn ME, Keeton KA, Gaffney SH, Sahmel J. Ambient Asbestos Fiber Concentrations and Long-Term Trends in Pleural Mesothelioma Incidence Between Urban and Rural Areas in the United States (1973-2012). Risk Analysis 2018;38(3):454-471 — M.M. Finkelstein (2018)
• Factors influencing long-term survival in mesothelioma patients--results of the German mesothelioma register — V. Neumann, A. Rütten, et al. (2004)
• Response to Letter to the Editor Regarding "Ambient Asbestos Fiber Concentrations and Long-Term Trends in Pleural Mesothelioma Incidence Between Urban and Rural Areas in the United States (1973-2012)" by Finkelstein — K.A. Keeton, M.E. Glynn, et al. (2018)
• Comparative long-term toxicity of Libby amphibole and amosite asbestos in rats after single or multiple intratracheal exposures — J.M. Cyphert, D.J. Carlin, et al. (2015)
• Incidence and familial risk of pleural mesothelioma in Sweden: a national cohort study — J. Ji, J. Sundquist, et al. (2016)

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