A meticulous new examination performed at the INFN laboratories in Milano-Bicocca and Pavia in Italy has shown that arsenic poisoning did not kill Napoleon. The researchers demonstrated that there is no evidence of a significant increase in the levels of arsenic in the emperor's hair during the final period of his life.

Physicists performed the study using a small nuclear reactor located at the university in Pavia, which was built for the Cryogenic Underground Observatory for Rare Events (Cuore) experiment. Currently in development at the INFN's National Laboratories in Gran Sasso, the completed Cuore facility will be the most advanced experiment for studying the rare phenomenon of neutrinoless double-beta decay and for measuring neutrino mass.

To examine Napoleon's hair, the team used the technique of neutron activation, which has two important advantages: it does not destroy the sample and it provides extremely precise results, even from samples with a small mass. The researchers placed Napoleon's hair in the core of the nuclear reactor in Pavia and used neutron activation to establish that all of the hair samples contained traces of arsenic. They chose to test for arsenic in particular because various historians have hypothesized that guards poisoned Napoleon during his imprisonment in Saint Helena. A diverse sample of hairs from different periods of Napoleon's life were examined, along with hair samples from people living today, to compare arsenic levels.

The examination produced some surprising results. First, the level of arsenic in all of the hair samples from 200 years ago is 100 times as great as the average level detected in samples from people living today. In other words, people at the beginning of the 19th century evidently ingested arsenic from the environment in quantities that are today considered dangerous. The other surprise is that there was no significant difference in arsenic levels between when Napoleon was a boy and during his final days in Saint Helena. According to the toxicologists who participated in the study, this provides evidence that this was not a case of poisoning, but rather the result of a lifetime's absorption of arsenic.