  We update constraints on cosmic opacity by combining recent SN Type Ia data
compilation with the latest measurements of the Hubble expansion at redshifts
between 0 and 2. The new constraint on the parameter $\epsilon$ parametrising
deviations from the luminosity-angular diameter distance relation
($d_L=d_A(1+z)^{2+\epsilon}$), is $\epsilon=-0.04_{-0.07}^{+0.08}$
(2-$\sigma$). For the redshift range between 0.2 and 0.35 this corresponds to
an opacity $\Delta\tau<0.012$ (95% C.L.), a factor of 2 stronger than the
previous constraint. Various models of beyond the standard model physics that
predict violation of photon number conservation contribute to the opacity and
can be equally constrained. In this paper we put new limits on axion-like
particles, including chameleons, and mini-charged particles.
