  We analyze the constraints on possible anomalous contributions to the
$W^+W^-Z$ vertex coming from non-universal radiative corrections to the $Z
\rightarrow b \bar{b}$ width. We parametrize these corrections in terms of
$\epsilon_b$ and use the LEP data to establish the allowed values for the
anomalous triple couplings. We examine all CP conserving effective operators
that exhibit $SU(2)_L\times U(1)_Y$ gauge invariance and do not give any tree
level contribution to the present experimental observables. For some of these
operators our constraints are comparable with the bounds coming from a global
fit of the oblique parameters, which evidences the increasing relevance of the
precise measurement of the $b$--quark parameters at LEP for the search of new
physics.
