The morbidity of the two isotopes in terms of absorbed radioactivity is almost exactly the same .
Plutonium - 238 is around 275 times more toxic by weight than plutonium - 239 .
Since the morbidity of the two isotopes in terms of absorbed radioactivity is almost exactly the same , plutonium - 238 is around 275 times more toxic by weight than plutonium - 239 .