  We consider the low energy effective chiral theory of QCD mesons and the
electroweak Goldstone bosons. In this effective theory the pion sector
contributes to the gauge boson masses and the Yukawa couplings of the fermions.
Consequently the Yukawa sector of quarks and leptons can have a $SU(2)_L\times
U(1)_Y\times U(1)_A$ global symmetry even with nonvanishing fermion masses. The
extra chiral $U(1)_A$ symmetry can be used to rotate the CP violating $\bar
\theta G\tilde G $ term away which therefore makes no contribution to low
energy CP violating effects like the neutron electric dipole momment. The
Goldstone mode associated with this $U(1)_A$ symmetry may be identified with
the $SU(2)$ singlet meson $\eta_0$.
