Bounds on $g_5^Z$ from Precision LEP Measurements
  The parity violating but CP conserving anomalous three-gauge-boson coupling $g_5^Z$ induces a universal contribution to the left-handed coupling of the $Z$ boson to fermions. We find that the LEP measurements of the partial $Z$ widths and lepton forward-backward asymmetries are sufficiently precise to place a bound of order $|g_5^Z|$ less than $\sim~10\%$. This bound is significantly better than what can be obtained at present from rare $K$ and $B$ meson decays. 
S. Dawson and G. Valencia