The incidence of thyroid cancer in the French population has been increasing for more than twenty years and has raised public concern about its association with the nuclear accident at Chernobyl. At the request of health authorities, a study has been launched to quantify the potential risk of thyroid cancer associated with the Chernobyl fallout in France. The aim was to determine if this risk would be observable through an epidemiological approach. The study considered the population living in eastern France and younger than 15 years at the time of the accident at the Chernobyl nuclear plant (26 April 1986). The number of spontaneous thyroid cancers in this population have been estimated from French cancer registries’ data. The thyroid doses for this population have been estimated from all available data about contamination in France and associated risks have been calculated with different risk models on the basis of a no-threshold linear dose-effect relation. Under this hypothesis, the number of excess cases of thyroid cancer ranges from 1.3 to 22 cases to compare with the 212 spontaneous cases excepted for the 1991-2000 period from 11.2 to 55.2 to compare with the 1,342 spontaneous cases expected for the 1991-2015 period. The corresponding percentages of excess cases range respectively from 0.5 to 10.5% and from 0.8 to 4.1%. These risk calculations indicate that the fallout from the Chernobyl accident cannot explain all of the increased incidence of thyroid cancers in France. On one hand, it is improbable that an epidemiological study could demonstrate the excess calculated in this study. On the other hand, the conditions for reinforcing the surveillance of thyroid cancers in France should be examined.
This work has been done with the Institut national de veille sanitaire and the Réseau Francim.