  We point out that the existence of metastable, tau > 10^3 s, negatively
charged electroweak-scale particles (X^-) alters the predictions for lithium
and other primordial elemental abundances for A>4 via the formation of bound
states with nuclei during BBN. In particular, we show that the bound states of
X^- with helium, formed at temperatures of about T=10^8K, lead to the catalytic
enhancement of Li6 production, which is eight orders of magnitude more
efficient than the standard channel. In particle physics models where
subsequent decay of X^- does not lead to large non-thermal BBN effects, this
directly translates to the level of sensitivity to the number density of
long-lived X^-, particles (\tau>10^5 s) relative to entropy of n_{X^-}/s <
3\times 10^{-17}, which is one of the most stringent probes of electroweak
scale remnants known to date.
