Occup Environ Med 67:187-195 doi:10.1136/oem.2008.045260
  • Environment

Prolonged time to pregnancy in residents exposed to ionising radiation in cobalt-60-contaminated buildings

  1. P-C Chen1,5
  1. 1Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University College of Public Health, Taipei, Taiwan
  2. 2Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK
  3. 3College of Public Health and Nutrition, Taipei Medical University, Taipei, Taiwan
  4. 4Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
  5. 5Department of Environmental and Occupational Medicine, National Taiwan University Hospital, Taipei, Taiwan
  6. 6Department of Family Medicine, National Taiwan University Hospital, Taipei, Taiwan
  7. 7Department of Health, Centers for Disease Control, Taipei, Taiwan
  1. Correspondence to Pau-Chung Chen, Institute of Occupational Medicine and Industrial Hygiene, College of Public Health, National Taiwan University, 17 Syujhou Road, Taipei 10055, Taiwan; pchen{at}
  1. Contributors P-CC conceived the study and supervised all aspects of its implementation. C-ML and WPC completed the analyses and draughted the content. PD, J-DW and L-TL assisted with the study design and revised the content. CLL contributed to the implementation of data collection. All authors helped to conceptualise ideas, interpret findings and review draughts of the manuscript.

  • Accepted 20 July 2009
  • Published Online First 22 September 2009


Objectives Radiation-induced cytogenetic damage in somatic cells has raised concern that low-dose ionising radiation can also damage germ cells and influence gamete production and/or function, resulting in decreased fertility. Time to pregnancy (TTP) was used to investigate whether exposure to γ-radiation affected fertility among the residents of cobalt-60-contaminated buildings in Taiwan.

Methods This was a retrospective pregnancy-based study of 357 pregnancies born to 124 exposed couples. Both the cumulative dose and the dose rate for each pregnancy was estimated based on a physical dose reconstruction programme. The comparison population consisted of 612 pregnancies born to 225 couples randomly sampled from the Taiwan general population. Information on TTP was collected by personal interviews. Fecundability ratios (FRs) were calculated with a discrete proportional hazards model.

Results For exposed mothers, fertility decreased significantly when unprotected intercourse began during the period of living in the radiation-contaminated buildings (FR 0.75, 95% CI 0.61 to 0.92). The effect was borderline significant for fathers (FR 0.83, 95% CI 0.68 to 1.02). There was evidence that prolonged TTP was associated with the rate of exposure for both mothers and fathers (tests for trend: female, p=0.0006; male, p=0.03), especially evident for dose rates ≥10 mSv/year (female, FR 0.60, 95% CI 0.43 to 0.84; male, FR 0.68, 95% CI 0.49 to 0.96).

Conclusions Our findings suggest that exposure to low-dose ionising radiation of cobalt-60-contaminated buildings may decrease fertility, especially in females. Fertility declined with increasing concurrent dose but not with cumulative dose.


  • * These authors contributed equally to this work.

  • Funding National Science Council, Taiwan (NSC 94-2314-B-002-312).

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the Ethic Review Board of the National Taiwan University College of Public Health.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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