A meta-analysis of leukaemia risk from protracted exposure to low-dose gamma radiation

Abstract

ContextMore than 400 000 workers annually receive a measurable radiation dose and may be at increased risk of radiation-induced leukaemia. It is unclear whether leukaemia risk is elevated with protracted, low-dose exposure.ObjectiveWe conducted a meta-analysis examining the relationship between protracted low-dose ionising radiation exposure and leukaemia.Data sourcesReviews by the National Academies and United Nations provided a summary of informative studies published before 2005. PubMed and Embase databases were searched for additional occupational and environmental studies published between 2005 and 2009.Study selectionWe selected 23 studies that: (1) examined the association between protracted exposures to ionising radiation and leukaemia excluding chronic lymphocytic subtype; (2) were a cohort or nested case–control design without major bias; (3) reported quantitative estimates of exposure; and (4) conducted exposure–response analyses using relative or excess RR per unit exposure.MethodsStudies were further screened to reduce information overlap. Random effects models were developed to summarise between-study variance and obtain an aggregate estimate of the excess RR at 100 mGy. Publication bias was assessed by trim and fill and Rosenthal's file drawer methods.ResultsWe found an ERR at 100 mGy of 0.19 (95% CI 0.07 to 0.32) by modelling results from 10 studies and adjusting for publication bias. Between-study variance was not evident (p=0.99).ConclusionsProtracted exposure to low-dose gamma radiation is significantly associated with leukaemia. Our estimate agreed well with the leukaemia risk observed among exposed adults in the Life Span Study (LSS) of atomic bomb survivors, providing increased confidence in the current understanding of leukaemia risk from ionising radiation. However, unlike the estimates obtained from the LSS, our model provides a precise, quantitative summary of the direct estimates of excess risk from studies of protracted radiation exposures.

Mortality associated with chronic external radiation exposure in the French combined cohort of nuclear workers

“…Our ERR/Sv is also higher than the estimated ERR/Sv found in the combined US study31 and in a meta-analysis of the risk of non-CLL leukaemia after chronic occupational or environmental exposure to ionising radiation 32. Despite improvement in the precision of the estimates compared to the previous analyses,6 19 the statistical uncertainties associated with our ERR/Sv estimates remain large.…”

Exposure to ambient air pollution in Canada and the risk of adult leukemia

“…Leukemia is one of the more difficult cancers to ascertain, due to the rapid onset of acute forms and the failure to capture these cases while they are alive, and has shown to have lower coverage than other cancers in the Provincial Cancer Registries (Zakaria, 2013). In addition, many environmental studies conducted using incident cases of leukemia have noted possible under ascertainment (Daniels and Schubauer-Berigan, 2011). It is often the case that higher concentrations of NO 2 are related to a greater density in the road network and higher volumes of traffic (Beckerman et al, 2008) and these areas more often than not comprise people in lower socioeconomic groups (Kershaw et al, 2013).…”

Leukaemia mortality and low-dose ionising radiation in the WISMUT uranium miner cohort (1946–2013)

“…A substantial number of studies in other populations with chronic exposure to low levels of low-LET show a positive effect with regard to non-CLL 2–4 7 8 10 12 13. Statistically significant associations were present, for example, in the recent pooled analyses of UK, French and US nuclear workers (n=531, ERR/Gy=2.96; 90% CI 1.17 to 5.21),8 in the LSS using data restricted to men exposed between the ages of 20 and 60 years (n=94, ERR/Sv=2.63; 90% CI 1.50 to 4.27),5 and in a recent meta-analysis by Daniels and Schubauer-Berigan (ERR/Gy=1.9; 95% CI 0.7 to 3.2) 13…”

“…Positive associations have been reported in nuclear worker studies,3–8 Chernobyl clean-up workers9–11 and the Techa river cohort 12. In a recent meta-analysis of 10 occupational and environmental studies with protracted low-dose exposure by Daniels and Schubauer-Berigan,13 an overall excess relative risk (ERR) at 100 mGy of 0.19 (95% CI 0.07 to 0.32) was found. This risk estimate is in reasonable agreement with the results of the LSS14 and a recently published large pooled analysis of nuclear worker studies 8…”