Elsevier

The Lancet

Volume 354, Issue 9188, 23 October 1999, Pages 1407-1414
The Lancet

Articles
Stillbirths among offspring of male radiation workers at Sellafield nuclear reprocessing plant

https://doi.org/10.1016/S0140-6736(99)04138-0Get rights and content

Summary

Background

Ionising radiation is a known mutagen, but few studies have examined transgenerational effects of paternal exposure in human beings. The workforce at the Sellafield nuclear reprocessing plant in the county of Cumbria, UK, is the most highly exposed workforce in western Europe and North America. This study, which is part of a larger programme of work investigating the health of the children of the Sellafield workforce, set out to find whether there was evidence of an association between stillbirth risk and paternal exposure to ionising radiation.

Methods

We collected details from birth registration documents for all singleton 248097 livebirths and 3715 stillbirths in the county of Cumbria 1950–89. Within this cohort the 130 stillbirths and 9078 livebirths to partners of male radiation workers employed at Sellafield were identified. Logistic regression was used to analyse the relation between stillbirth risk and father's preconceptional radiation exposure, with adjustment for social class, year of birth, father's age, and birth order.

Findings

A significant positive association was found between the risk of a baby being stillborn and the father's total exposure to external ionising radiation before conception (adjusted odds ratio per 100 mSv 1·24 [95% Cl 1·04–1·45], p=0·009). The risk was higher for stillbirths with congenital anomaly and was highest for the nine stillbirths with neural-tube defects. The statistical models predicted that, were the association to be interpreted as causal, between 0 and 31·9 of the 130 stillbirths to the workforce may be attributable to father's radiation exposure.

Interpretation

The findings of an increased risk of stillbirth with increasing paternal occupational exposure to external radiation are qualitatively consistent with those from animal models, though the risk estimate is higher. Although we cannot exclude the possibility of an unmeasured risk factor for stillbirth, confounded with paternal preconceptional irradiation, extensive checks confirmed that the statistical models were a good fit to the data and there was not statistical evidence of unmeasured factors.

Introduction

There has been concern about possible transgenerational effects of exposure to ionising radiation since the earliest days of radiobiological research. Exposure of male mammals to preconceptional ionising radiation causes a range of adverse outcomes in their offspring, including death, cancer, and congenital anomaly.1, 2, 3, 4, 5 In 1988 a UK government committee6 investigating the excess risk of leukaemia in children in the vicinity of the Dounreay nuclear-fuel reprocessing plant in the north of Scotland recommended that “epidemiological studies should be set up to consider any possible effects on the health of the offspring of parents occupationally exposed to radiation”. This concern received further emphasis in 1990 when Gardner and colleagues7 reported the results of a case-control study of young people diagnosed with leukaemia and lymphoma in west Cumbria, UK, concluding that the substantial excess of these malignant disorders in young people in Sellafield could be the result of their fathers' preconceptional radiation exposure while employed at Sellafield, the adjacent nuclear-fuel reprocessing plant, with exposure during the period immediately before conception being particularly important. However, the hypothesis that paternal preconceptional irradiation is causally associated with childhood leukaemia and lymphoma has not been supported by further epidemiological investigations.8, 9, 10, 11

Any transgenerational effects of paternal preconceptional irradiation would be likely to appear as outcomes such as congenital anomalies rather than childhood leukaemia since these have a much higher heritable component.12 The Sellafield workforce is of particular interest because of its comparatively high exposures to ionising radiation.13 The current programme of work set out to study transgenerational effects of paternal preconceptional irradiation in the offspring of this workforce, by investigating the association of such irradiation with the sex ratio and adverse health outcome in their children (stillbirth, infant death, cancer).8, 14, 15, 16 The present study investigated whether there was evidence of increasing risk of stillbirth (including those with congenital anomaly), within the cohort of children born to male radiation workers at the Sellafield site, with increasing external or internal preconceptional exposure to ionising radiation during either the 90 days immediately before conception (ie, during the period of spermatogenesis), or the entire preconceptional period of employment within the nuclear industry.

Section snippets

Participants

A cohort study was done of all singleton births from 1950 to 1989 to fathers employed at Sellafield while resident in the county of Cumbria. Preconceptional radiation doses were estimated from annual external dose summaries and from routine internal dose assessments. Doses in the 90 days before conception were estimated pro rata from annual dose summaries. Investigation of the relation between paternal preconceptional irradiation and stillbirth by specific cause was possible only from 1961

Non-Sellafield cohort

The distribution of births by decade, social class, and birth order is shown in table 1. Sex was not a significant risk factor for stillbirth. The best fit for the change in stillbirth rate by year of birth was a cubic model, adjusted for social class and birth order (Pearson χ21022=1005, p=0·64). The model predicted 99·9 stillbirths (96 observed) among children conceived by fathers who were subsequently employed at Sellafield and 18·1 stillbirths (21 observed) in children of non-radiation

Discussion

Stillbirth risk was significantly associated with total external paternal preconceptional irradiation in both the cohort and case-control studies. The risk was higher for stillborn babies with congenital anomalies, in particular those with neural-tube defects. In the cohort study there was also a significant association with ASD90, but no association was found with FB90 in the case-control study, suggesting that this may have been an artefact caused by the use of pro-rata 90-day dose estimates

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