M_\odot$, and $0.51\,+ $ $>$$0.59\, M_\odot$, the last being a single-lined system with only a lower limit for the secondary. We assume that each WD arose from a solar-metallicity star and map from the WD masses to the initial stellar masses using the results of @Umeda:1998ij, mapping then to the WD masses calculated for these stellar masses at other metallicities. The $0.5\,M_\odot$ cut allows a straightforward translation without regards to systems with low-mass He WDs, etc. Keeping the initial binary separations fixed, we calculate the merger time due to gravitational wave losses for each system (see, e.g., @Thompson:2010dp). Fig. \[masses\] displays the effect on these systems using this prescription, where it is seen that the total masses of all three systems would have been pushed beyond the Chandrasekhar mass limit and the merger time would have been significantly reduced at lower metallicities.

There is hope for new tests to reduce the uncertainty in the overall effect of metallicity. For example, in observations of SN Ia host galaxies we would expect the hosts of SN Ia to be slightly less metal-rich than the galaxy population as a whole for fixed galaxy mass. This effect would not be as marked as in 