  We use Sloan Digital Sky Survey Data Release 2 QSO spectra to constrain the
dust-reddening caused by intervening damped Lyman-alpha systems (DLAs).
Comparing the spectral index distribution of a 70 sight-line DLA sample with
that of a large control sample reveals no evidence for dust-reddening at z~3.
Our limit on the shift in spectral index, |Delta(alpha)| < 0.19 (3-sigma),
corresponds to a limit on the colour excess due to SMC-like dust-reddening,
E(B-V) < 0.02 mag (3-sigma). This is inconsistent with the early studies of
Fall, Pei and collaborators who used the small QSO and DLA samples available.
Comparison of the DLA and control magnitude distributions also reveals >2-sigma
evidence for an excess of bright and/or a deficit of faint QSOs with foreground
DLAs. Higher equivalent width DLAs give a stronger signal. We interpret this as
the signature of gravitational magnification due to the intervening DLAs.

Astrophysics