  The evolution equation for active and sterile neutrinos propagating in
general anisotropic or polarized background environment is found and solved for
a special case when heavy neutrinos do not decouple, resulting in non-unitary
mixing among light neutrino states. Then new CP violating neutrino oscillation
effects appear. In contrast to the standard unitary neutrino oscillations these
effects can be visible even for two flavour neutrino transitions and even if
one of the elements of the neutrino mixing matrix is equal to zero. They do not
necessarily vanish with $\delta m^{2} \to 0$ and they are different for various
pairs of flavour neutrino transitions ($\nu_e \to \nu_\mu$), ($\nu_\mu \to
\nu_\tau$), ($\nu_\tau \to \nu_e$). Neutrino oscillations in vacuum and Earth's
matter are calculated for some fixed baseline experiments and a comparison
between unitary and non-unitary oscillations are presented. It is shown, taking
into account the present experimental constraints, that heavy neutrino states
can affect CP and T asymmetries. This is especially true in the case of
$\nu_\mu \to \nu_\tau$ oscillations.
