Abstract: Decays of relic particles into neutrinos can leave a strong imprint on the light elements formed during Big Bang Nucleosynthesis (BBN) if the decay happens before recombination. In this talk, I will discuss the effect of injecting neutrinos at lifetimes larger than 10⁴ s, focusing on the disintegration of the light elements. Several key processes are at play, including final-state radiation from the decay, as well as subsequent neutrino interactions with both neutrinos from the background or other non-themal neutrinos. These processes can lead to the production of electromagnetic and hadronic material, triggering late-time photodisintegration and hadrodisintegration reactions, i.e. the destruction of light elements that have previously been formed during BBN. I will show how the resulting constraints significantly impact a wide range of relic particle masses and lifetimes, covering regions that were previously unconstrained.