  The persistent discrepancy between observations of 7Li with putative
primordial origin and its abundance prediction in Big Bang Nucleosynthesis
(BBN) has become a challenge for the standard cosmological and astrophysical
picture. We point out that the decay of GeV-scale metastable particles X may
significantly reduce the BBN value down to a level at which it is reconciled
with observations. The most efficient reduction occurs when the decay happens
to charged pions and kaons, followed by their charge exchange reactions with
protons. Similarly, if X decays to muons, secondary electron antineutrinos
produce a similar effect. We consider the viability of these mechanisms in
different classes of new GeV-scale sectors, and find that several minimal
extensions of the Standard Model with metastable vector and/or scalar particles
are capable of solving the cosmological lithium problem. Such light states can
be a key to the explanation of recent cosmic ray anomalies and can be searched
for in a variety of high-intensity medium-energy experiments.
