  We develop, from first principles, a general and compact formalism for
predicting the electromagnetic response of a metamaterial with non-magnetic
inclusions in the long wavelength limit, including spatial dispersion up to the
second order. Specifically, by resorting to a suitable multiscale technique, we
show that medium effective permittivity tensor and the first and second order
tensors describing spatial dispersion can be evaluated by averaging suitable
spatially rapidly-varying fields each satysifing electrostatic-like equations
within the metamaterial unit cell. For metamaterials with negligible
second-order spatial dispersion, we exploit the equivalence of first-order
spatial dispersion and reciprocal bianisotropic electromagnetic response to
deduce a simple expression for the metamaterial chirality tensor. Such an
expression allows us to systematically analyze the effect of the composite
spatial symmetry properties on electromagnetic chirality. We find that even if
a metamaterial is geometrically achiral, i.e. it is indistinguishable from its
mirror image, it shows pseudo-chiral-omega electromagnetic chirality if the
rotation needed to restore the dielectric profile after the reflection is
either a $0^\circ$ or $90^\circ$ rotation around an axis orthogonal to the
reflection plane. These two symmetric situations encompass two-dimensional and
one-dimensional metamaterials with chiral response. As an example admitting
full analytical description, we discuss one-dimensional metamaterials whose
single chirality parameter is shown to be directly related to the metamaterial
dielectric profile by quadratures.
