  We estimate the magnitude of charge symmetry breaking effects in deep
inelastic scattering from nuclei. The resulting contribution to systematic
uncertainties in hadronic determinations of $sin^2\theta_W$ are found to be
less than the current experimental accuracy, but may be important in the
analyses of more precise future experiments. We expect the largest nuclear
charge symmetry breaking effects in the Paschos-Wolfenstein ratio $R^-$, where
the resulting uncertainty in the determination of $sin^2 \theta_W$ reaches
$10^{-3}$.
