  We can be biased against observing massive black holes to merge in the local
universe as the bounds on the maximum black hole mass ($M_{BH}^{\rm max}$)
depends on the assumptions regarding the metallicity evolution of the star
forming gas across the cosmic time. We investigate the bounds on the
metallicity evolution, mass distribution and delay times of the binary black
hole sources based on the ten observed events by LIGO. We parametrize
$M_{BH}^{\rm max}$ to be a function of metallicity which itself is modeled to
evolve with redshift in either a modest or rapid fashion. Rapid metallicity
evolution models predict a stringent bound of $M_{BH}^{\rm
max}=44^{+9}_{-5}M_{\odot}$, while the bound on $M_{BH}^{\rm max}$ in the
models with modest metallicity evolution is $M_{BH}^{\rm max}=52^{+16}_{-9}
M_{\odot}$. Therefore, inferring $M_{BH}^{\rm max}$ from GW data depends on the
assumed metal enrichment history of the universe that is not severely
constrained at the moment.
