Launched in 2005, the EPICE (evaluation of diseases induced by caesium 137 contamination) research program aims to study non-cancerous effects that may result from exposure to low doses of ionizing radiation. The program aims to assess whether chronic caesium contamination may induce cardiac arrhythmias and lens opacities (early stages of cataract development). To answer this question, IRSN has set up two epidemiological studies to collect scientific data with the aim of answering a social question regarding the health consequences of the Chernobyl nuclear accident among a sensitive group (children). These studies were conducted in Russia's south-western region of Bryansk, which includes both caesium-137contaminated areas and uncontaminated areas, in collaboration with the Clinical Diagnostic Center (Bryansk), as well as local schools and hospitals.
Background and objectives
Currently available scientific data on the health consequences of accidental exposure to ionizing radiation are based mainly on lessons learned from the monitoring of cohorts from Hiroshima and Nagasaki in Japan, as well as population groups in Belarus, Ukraine and Russia exposed to the fallout from the Chernobyl accident. The effects observed vary according to the type of radiation exposure, dose rate, duration of exposure and the study population.
In the long term (from a few years to decades), an increase in the risk of leukemia and cancers has been observed among survivors of the Hiroshima and Nagasaki bombs, as well as an increase in thyroid cancer in children exposed to fallout from the Chernobyl accident.
With regards to non-cancer effects, a relationship between the risk of cardiovascular disease and lens opacities (early stages of cataract development) and exposure to ionizing radiation was observed among survivors of the Hiroshima and Nagasaki bombs and in Chernobyl clean-up workers. This relationship has been observed in population groups that have been exposed to high doses of ionizing radiation, but major uncertainties persist over the existence of such relationships at low doses.
The EPICE program, launched by IRSN in 2005 in collaboration with the Clinical Diagnostic Center (Bryansk), aims to remove some of these uncertainties concerning children. The study took place in Bryansk Oblast (Russia), a region northeast of the Chernobyl nuclear power plant, part of which was contaminated by caesium-137 deposits following the accident of 1986. Caesium is still present in these areas in concentrations of up to 3,700 kBq/m². Residents of contaminated areas are therefore exposed to external contamination from their environment and internal contamination mainly from the ingestion of forest products (mushrooms, berries, game) known to be heavily contaminated with caesium-137; residents of non-contaminated areas may also be exposed to internal contamination from ingestion of products from contaminated areas. Two comparable groups (distribution in gender and age) of approximately 18,000 children were monitored for 4 years each, 2009-2013 and 2013-2017 respectively, some of them living in non-contaminated areas (caesium-137 < 37 kBq/m²) in Bryansk Oblast and the other part in contaminated areas (caesium-137 > 555 kBq/m²). Research was conducted taking into account their internal contamination level, their place of residence and the existence of cardiac arrhythmias or lens opacities.
© UNSCEAR - caesium-137 soil deposition
The main scientific and technical objectives of the EPICE program are:
- To identify non-cancerous pathologies, in particular cardiac arrhythmias and lens opacities, presented by children living in Russian territories contaminated by fallout from the Chernobyl accident;
- To study the main possible etiologies (study of the causes and factors of a disease) of these pathologies;
- To evaluate the level of caesium-137 contamination presented by these children;
- To confirm or invalidate the existence of an association between chronic ingestion of caesium-137 through diet and these pathologies.
A pilot study of a group of 49 children conducted in 2005-2006 confirmed the feasibility of a multi-year program on a population of statistically significant size.
The program then took place in two phases.
Phase 1: Study of cardiac arrhythmias
The first phase of the program, which ran from 2009 to 2013, focused on the study of cardiac arrhythmias. This work aimed to identify, among a population group of 18,152 children living in Bryansk Oblast (areas contaminated with caesium 137 versus uncontaminated areas), children with rhythm or conduction disorders which cannot be explained by any other known etiology (congenital malformation in particular).
The purpose of this epidemiological study was to determine the prevalence1 of cardiac arrhythmias and to assess whether or not caesium-137 was a factor associated with these arrhythmias. The systematic screening campaign for cardiac arrhythmias started in the field in May 2009 and continued for 4 years. For each child in the study population, an electrocardiogram, echocardiography, and caesium-137 whole-body activity measurement were performed. A 24-hour monitoring of cardiac electrical parameters (Holter) and blood tests with the major biological parameters were also made for some children. Together, these examinations made it possible to diagnose whether or not each child had a cardiac disorder, and to look for a possible link with caesium-137 contamination and whether or not their place of residence was in a contaminated area. The information was collected in a database and interpreted under the control of IRSN.
To carry out this action, the Clinical Diagnostic Center (Bryansk) set up two medical teams dedicated to implementing this program, who traveled from school to school. All examinations were carried out on site in partnership with the heads of local schools and hospitals, with the exception of the blood tests, which were carried out in Bryansk. In addition, only children whose parents had given advance written consent participated in this program.
Prevalence is the frquency of people with a disease in a population at a given time
Phase 2: Study of lens opacities
The second phase of the program was implemented in 2012. It covered the study of lens opacities in a population group equivalent to the one examined during the first phase. The screening campaign took place between 2013 and 2017 under conditions similar to those for cardiac arrhythmias. The first results of the collected data should be published by 2019-2020.
The first phase of the EPICE program for which the results were published in the British Medical Journal Open periodical of March 2018, diagnosed 2,526 children with cardiac arrhythmias, 1,172 living in contaminated areas and 1,354 living in uncontaminated areas. After a thorough statistical analysis of the data collected in the field over the 2009-2013 period, the estimated prevalence of cardiac arrhythmias in the contaminated areas (13.3%) is significantly lower than in the uncontaminated areas (15.2%); with regard to the whole-body caesium-137 activity, no association could be identified. Caesium-137 is therefore not a factor associated with the observation of cardiac arrhythmia within the EPICE study.
The results of the second phase on the study of lens opacities are expected in 2019-2020.