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Cancer
risk among chernobyl cleanup workers in Estonia and Latvia, 1986-1998
Mati Rahu 1 2 *, Kaja
Rahu 1 2, Anssi Auvinen 3 4, Mare
Tekkel 1 2, Aivars Stengrevics 5, Timo
Hakulinen 6, John D. Boice Jr 7 8, Peter
D. Inskip 9
1Department of
Epidemiology and Biostatistics, National Institute for Health
Development, Tallinn, Estonia. 2Estonian Centre of
Excellence in Behavioural and Health Sciences, Tartu-Tallinn, Estonia.
3STUK - Radiation and Nuclear Safety Authority,
Helsinki, Finland. 4School of Public Health, University of
Tampere, Tampere, Finland. 5Latvian Cancer Registry, Riga,
Latvia. 6Finnish Cancer Registry, Helsinki, Finland. 7International
Epidemiology Institute, Rockville, Maryland. 8School of
Medicine, Vanderbilt University, Nashville, Tennessee. 9Radiation
Epidemiology Branch, Division of Cancer Epidemiology and
Genetics,National Cancer Institute, NIH, Bethesda, Maryland.
*Correspondence to Mati Rahu, Department of Epidemiology
and Biostatistics, National Institute for Health Development, Hiiu 42,
11619 Tallinn, Estonia. Email: Mati Rahu (mati.rahu@tai.ee). Fax:
372-659-3901
Received: 29 July 2005; Accepted: 7 November 2005
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Two cohorts of Chernobyl cleanup workers
from Estonia (4,786 men) and Latvia (5,546 men) were followed from
1986 to 1998 to investigate cancer incidence among persons exposed to
ionizing radiation from the Chernobyl accident.
Each cohort was identified from various independent sources and
followed using nationwide population and mortality registries.
Cancers were ascertained by linkage with nationwide cancer
registries.
Overall, 75 incident cancers were identified in the Estonian cohort
and 80 in the Latvian cohort.
The combined-cohort standardized incidence ratio (SIR) for all cancers
was 1.15 (95% confidence interval (CI) = 0.98-1.34) and for leukemia,
1.53 (95% CI = 0.62-3.17; n = 7).
Statistically significant excess cases of thyroid (SIR = 7.06, 95% CI
= 2.84-14.55; n = 7) and brain cancer (SIR = 2.14, 95% CI =
1.07-3.83; n = 11) were found, mainly based on Latvian
data.
However, there was no evidence of a dose response for any of these
sites, and the relationship to radiation exposure remains to be
established.
Excess of thyroid cancer cases observed may have been due to
screening, the leukemia cases included 2 unconfirmed diagnoses, and
the excess cases of brain tumors may have been a chance finding.
There was an indication of increased risk associated with early entry
to the Chernobyl area and late follow-up, though not statistically
significant.
Further follow-up of Chernobyl cleanup workers is warranted to clarify
the possible health effects of radiation exposure.
Keywords. Neoplasms,
incidence, cohort, Chernobyl, Estonia, Latvia, radiation effects
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