Leukaemia Incidence in Children and Adults in the Regions of Russia Most Highly Contaminated after the Chernobyl Nuclear Power Plant Accident

ABSTRACT BACKGROUND Leukaemia, especially the acute types
predominant in children, may be caused by ionizing radiation. After
the Chernobyl Nuclear Power Plant accident on 26 April 1986, parts
of Belarus, Russia and the Ukraine were contaminated with
radionuclides. To date, over 270 000 people live in such
contaminated regions in Russia. This study investigates whether the
leukaemia incidence rates in these regions might have increased due
to the radiation. MATERIALS & METHODS A prospective
population-based cohort study with a control group was carried out.
Cases of leukaemia previously not registered were actively sought
for in medical and administrative institutions. Each case that had
occurred in the study regions between 1980 and 1998 has been
ascertained and verified. A descriptive analysis was then performed
on the resulting data base which included 333 leukaemia cases.
RESULTS There is a slight secular trend in the standardized
incidence rates both in the highly contaminated and in the control
regions. This increase, however, is more marked in the control
regions. The incidence rates in children (0-14) in the highly
contaminated regions decrease between the pre-accident (1980 to
1986) and the first post-accident period (1987-1992) and show a
slight increase towards the second post-accident period
(1993-1998), whereas the incidence rates in the control regions
show exactly the opposite dynamic. This makes a connection between
the dynamics of the incidence rates and the radiological situation
highly improbable. The comparative analysis of the leukaemia
incidence rates has not revealed a statistically significant
difference between the population of the highly contaminated
regions of the Bryansk oblast and the combined control regions of
the Kaluga oblast. CONCLUSIONS There is so far no indication of an
increase in leukaemia incidence rates in the general population,
neither for children nor for adults. This does not contradict the
current radiobiological knowledge that cancer, especially
leukaemia, can be caused by ionizing radiation. The number of
expected radiation-induced cases based on the risk estimates from
the Japanese cohort lies within the 95% confidence limits of the
spontaneous incidence rates. It would therefore, if at all present,
not be statistically detectable in a population of 222 000 with a
spontaneous rate of 5.4/100 000 in men and 3.3/100 000 in women in
the control regions. Considering the latency periods and the
age-dependent risk-curve of radiation-induced cancers, it is highly
unlikely that a radiation-related increase in leukaemia or solid
tumour incidence rates will become obvious in the future. The fear
and apprehension caused by the overestimation of the radiation
risks create a continuous stress situation and add to the present
detrimental health conditions in the population. It is therefore of
utmost importance to communicate not only the results but also the
reliability of the study and the soundness of the data to the
affected people.