Last update on November 2012
The aim of the Freebird (Fukushima Radiation Exposure and Effects in BIRD populations, ANR-11-JAPN-003 project) project, launched in 2011, is to study the effects of ionising radiation in birds in the contaminated zone situated 100 km around Fukushima. This project is being conducted by IRSN (Radionuclides Ecotoxicology Laboratory) with Arizona State University - Tempe (United States) and Tsukuba University (Japan) and aims to determine whether links exist between the doses received by birds, observed physiological modifications and their consequences on reproduction. This project is financed in the frame of a call for tender organised by the French Research National Agency (ANR) and Japanese Science and Technology Agency (JST).
Context and issues at stake
The primary mechanisms of the effects of ionising radiation are known, particularly on DNA, but the consequences on an ecological scale of chronic exposure, in a contaminated zone, remain difficult to predict. Research carried out on bird populations living in the Chernobyl exclusion zone (following the accident in 1986) has highlighted not only deleterious effects on biodiversity and the abundance of species but also damage to the DNA of these same species, including malformations of spermatozoids, albinism, oxidative stress, etc. (Moller, Mousseau et al.). However, the interpretation of the relationships between ambient dose rates and effects is not unanimous within the scientific community. In fact, the effects highlighted seem very important in comparison to the low ambient dose rates measured (0.01 to 10 µGy/h).
Studied sites (black zones) around Fukushima. The dose rates are represented with graduated colors from blue (< 1 µSv/h) to red (> 10 µSv/h). © IRSN
The Fukushima nuclear catastrophe, which occurred in 2011, led to the massive release of volatile fission products (134Cs, 137Cs, 131I, 129mTe, 129Te, 132Te, 136Cs, 132I, 89Sr, 90Sr, etc.). The dose rates induced by radioactive deposits in the zone 80 kilometres around the damaged power plant are, in certain points of the north-west lobe where the deposits have been highest, above the maximum threshold defined for good conservation of ecosystems (10 µGy/h). The issues at stake of the Freebird project are thus:
To complete scientific knowledge on the conservation of species and the long term management of ecosystems contaminated by Fukushima.
To acquire new scientific results on the ecotoxic effects of ionising radiation, in response to public concerns.
To validate current concepts of radiation protection, which serve as the basis for ecosystem protection criteria.
Organisation of the project
The observations concern three species of bird: the Barn swallow, the Eurasian tree sparrow and the grey-capped greenfinch.
Observed bird species : the Barn swallow, the Eurasian tree sparrow, the grey-capped greenfinch (from left to right) © IRSN
The project is broken down into four successive tasks.
How have the birds been exposed to contamination?
The researchers are cross-tabulating existing data on radioactive contamination within a radius of 100 kilometres around Fukushima and knowledge of the periods and the areas of reproduction of the birds. They are constructing a mapping of the risk a priori, based on the reconstruction of the doses potentially absorbed by the different bird species (total doses for all irradiation routes - external and internal). This map can then be validated by measures acquired in the field, enabling an a posteriori mapping to be established.
How do the birds react physiologically to the radiation?
The work is based on the observation of the action of oxidative stress (caused by radiation induced reactive oxygen species) on antioxidants, particularly vitamin E and carotenoids, the latter also being involved in plumage coloration. The researchers also observe damage to DNA, the immunostimulating effect of anti-oxidants, the hormonal response to stress in chronic exposure conditions, fertility and sperm quality.
How does the exposure to radiation affect the birds during the breeding season?
The work then involves observing the effects of radiation at the organism scale: the evolution of sexual signals (plumage coloration) as well as maternal investment in eggs (number, weight and size of eggs).
How does the exposure to radiation affect an entire population?
This latter task consists in modelling the evolution of bird populations and dose-biological response relationships.
Sequencing of the project
Freebird began in October 2011 and is scheduled to last 18 months. Field studies around Fukushima (choice of study sites, optimisation of protocols, sampling campaign outside of reproduction) and a collection of data on birds reproducing in the Fukushima zone were conducted between October and December 2011. In mid-January, a campaign of sampling and bird captures was carried out in the 11 sites chosen in the 100 kilometre zone (a control site and ten sites with different levels of radioactivity, from 0.75 µSv/h to 10 µSv/h). Dosimeters have been installed in these zones.
Dosimetre implantation © IRSN
The next biological sampling and capture campaign is scheduled for Spring 2012, during the birds’ period of reproduction. The samples collected will then be analysed at ASU - Tempe and IRSN.