  We use the worldline formalism for calculating the one-loop effective action
for the Einstein-Maxwell background induced by charged scalars or spinors, in
the limit of low energy and weak gravitational field but treating the
electromagnetic field nonperturbatively. The effective action is obtained in a
form which generalizes the standard proper-time representation of the
Euler-Heisenberg Lagrangian. We compare with previous work and discuss possible
applications.
