  The effective Lagrangian of QED coupled to dyons is calculated. The resulting
generalization of the Euler-Heisenberg Lagrangian contains non-linear P and T
noninvariant terms corresponding to the virtual pair creation of dyons. The
corresponding P and T violating part of the matrix element for light-by-light
scattering is considered. This effect induces an electric dipole moment for the
electron, of order M^{-2}, where M is the dyon mass. The current limit on the
electric dipole moment of the electron yields the lower dyon mass bound M > 1
TeV.
