What actually happened is Joliot turned into a supervilain, he killed Pierre Curie before he could become a superhero, but was ultimately defeated by Henri Bequerel, who is immortal.
I thought this was common knowledge.
In the meantime Irene Joliot died of the radiations, as everybody would expect.
In Europe, 40% of emissions come from private cars. If we remove all other emissions, we still can't reach the factor of 4 just because of cars. Are you sure your source isn't BP?