Parental occupational exposure and risk of childhood central nervous system tumors: a pooled analysis of case-control studies from Germany, France, and the UK

Our plain-English summary of Parental occupational exposure and risk of childhood central nervous system tumors: a pooled analysis of case-control studies from Germany, France, and the UK, by C. Huoi, A. Olsson, T. Lightfoot, et al (Cancer Causes & Control, 2014).

The study

• Authors: C. Huoi, A. Olsson, T. Lightfoot, E. Roman, J. Clavel, B. Lacour, P. Kaatsch, H. Kromhout, R. Vermeulen, S. Peters, H.D. Bailey, J. Schüz
• Journal: Cancer Causes & Control
• Published: 2014;25(12):1603-13
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: To assess the risk of childhood central nervous system (CNS) tumors associated with parental occupational exposure to polycyclic aromatic hydrocarbons (PAH), diesel motor exhaust (DME), asbestos, crystalline silica, and metals, which are established carcinogens in adults.

Methods: We pooled data from three population-based case-control studies from Germany, France, and the UK. Cases were children aged up to 15 years and diagnosed with CNS tumor, and controls were frequency-matched by age and sex. Socio-demographic data and parental occupation around conception/pregnancy and at diagnosis were collected using standardized interviews, face-to-face or by telephone. A general population job-exposure matrix was used to assign a level of exposure to each job. Logistic regression models were fitted to compute odds ratios and 95 % confidence intervals.

Results: Our study included 1,361 cases of CNS tumors and 5,500 controls. Paternal exposure to PAH, asbestos, and metals around conception was associated with an increased moderate risk of CNS tumors, although statistically non-significant. The association with exposure to asbestos around conception and diagnosis was stronger when fathers were exposed to high levels. Paternal exposure to DME and silica, and maternal exposure to PAH, DME, asbestos, silica, and metals, were not associated with an increased risk of CNS tumors.

Conclusion: Our large pooled study showed weak evidence of a modest association between paternal occupational exposure to PAH and CNS tumor risk. Our findings need further exploration in the future studies.

In plain English

The authors pooled three population-based case-control studies from Germany (1988–1994), France (2003–2004) and the UK (1991–1996). Together these covered 1,361 children under 15 with central nervous system (CNS) tumors and 5,500 control children. Each parent's job was given an exposure level from a general population job-exposure matrix. The matrix covered polycyclic aromatic hydrocarbons (PAH), diesel motor exhaust, asbestos, crystalline silica, and metals (chromium and nickel). For fathers' asbestos exposure around conception, the odds ratio was 1.12 (95% confidence interval 0.95 to 1.32). For high exposure it was 1.42 (0.87 to 2.32). Neither result was statistically significant. Fathers' asbestos exposure around conception was significantly associated with the 'other' tumor subgroup (odds ratio 1.32, 1.01 to 1.70). The result for fathers' asbestos varied moderately between countries. No maternal exposure was associated with CNS tumors. The authors concluded there was weak evidence of a modest association with fathers' PAH exposure. They called the asbestos findings intriguing but in need of confirmation. They noted that the matrix could not capture specific tasks, exposure duration or exposure at home, and that multiple comparisons could produce chance findings.

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: pooled analysis of three population-based case-control studies, with a meta-analysis of differences between countries
• Who was studied: 1,361 children under 15 with CNS tumors and 5,500 controls from case-control studies in Germany (1988–1994), France (2003–2004) and the UK (1991–1996); cases included 446 astrocytomas, 374 CNS embryonal tumors, 152 ependymomas and 389 other tumors
• Exposure: Parental occupational exposure to PAH, diesel motor exhaust, asbestos (fiber type not specified), crystalline silica, chromium and nickel (the last two merged as 'metals'). Exposure was assigned from job titles by the DOM-JEM job-exposure matrix as none, low or high. Fathers were assessed around conception and at diagnosis; mothers during pregnancy and at diagnosis. No asbestos exposure was assigned after each country's ban.
• Main results:
  • Fathers' asbestos exposure around conception: OR 1.12, 95% CI 0.95–1.32 (244 exposed cases, 790 exposed controls), not statistically significant
  • Fathers' asbestos exposure around diagnosis: OR 1.05, 95% CI 0.84–1.32
  • For fathers with high asbestos exposure, odds ratios were higher than for low exposure but not significantly elevated: OR 1.42 (0.87–2.32) around conception and OR 1.61 (0.79–3.26) around diagnosis
  • Fathers' asbestos exposure around conception was significantly associated with the 'other' CNS tumor subgroup: OR 1.32, 95% CI 1.01–1.70
  • Results for fathers' asbestos exposure varied moderately between the three countries (I-squared 59.5%). The German study showed a significant increased risk, opposite to the French study, where the prevalence of asbestos exposure was lower (5.6% versus 18.3% in Germany and 21.2% in the UK).
  • No maternal exposure was associated with CNS tumors. Maternal asbestos exposure during pregnancy: OR 1.03, 95% CI 0.65–1.63 (24 exposed cases, 102 exposed controls).
  • Fathers' PAH exposure around conception: OR 1.22, 95% CI 0.98–1.52, not statistically significant
• The authors' conclusion: The authors concluded there was weak evidence of a modest association between fathers' occupational PAH exposure and CNS tumor risk. They considered the asbestos findings intriguing but in need of confirmation in further investigations.
• Limitations the authors state:
  • The general population job-exposure matrix could not account for specific tasks or country differences, which may have caused exposure misclassification
  • Duration of exposure and changes in intensity over time could not be considered
  • Possible exposure of parents and children at home was not taken into account
  • Converting German and UK job codes between classification systems may have added exposure misclassification
  • Unmeasured confounders cannot be ruled out
  • Multiple comparisons may have produced a statistically significant result by chance
  • The French study recruited only malignant CNS tumors, so astrocytomas were underrepresented

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Meta-Analysis, Crystalline, Odds Ratio, confidence interval.

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