  In this work, we use two gas mass fraction samples of galaxy clusters
obtained from their X-ray surface brightness observations jointly with recent
$H(z)$ data in a flat $\Lambda$CDM framework to impose limits on cosmic
opacity. It is assumed that the galaxy clusters are in hydrostatic equilibrium
and their gas mass fraction measurement is constant with redshift. We show that
the current limits on the matter density parameter obtained from X-ray gas mass
fraction test are strongly dependent on the cosmic transparency assumption even
for a flat scenario. Our results are consistent with a transparent universe
within $1\sigma$ c.l. in full agreement with other analyses which used type Ia
supernovae, gamma ray burst and $H(z)$ data.
