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Previously we used the Nearby Supernova Factory sample to show that SNe~Iahaving locally star-forming environments are dimmer than SNe~Ia having locallypassive environments.Here we use the \constitution\ sample together with hostgalaxy data from \GALEX\ to independently confirm that result. The effect isseen using both the SALT2 and MLCS2k2 lightcurve fitting and standardizationmethods, with brightness differences of $0.094 \pm 0.037\ \mathrm{mag}$ forSALT2 and $0.155 \pm 0.041\ \mathrm{mag}$ for MLCS2k2 with $R_V=2.5$. Whencombined with our previous measurement the effect is $0.094 \pm 0.025\\mathrm{mag}$ for SALT2. If the ratio of these local SN~Ia environments changeswith redshift or sample selection, this can lead to a bias in cosmologicalmeasurements. We explore this issue further, using as an example the directmeasurement of $H_0$. \GALEX{} observations show that the SNe~Ia havingstandardized absolute magnitudes calibrated via the Cepheid period--luminosityrelation using {\textit{HST}} originate in predominately star-formingenvironments, whereas only ~50% of the Hubble-flow comparison sample havelocally star-forming environments. As a consequence, the $H_0$ measurementusing SNe~Ia is currently overestimated. Correcting for this bias, we find avalue of $H_0^{corr}=70.6\pm 2.6\ \mathrm{km\ s^{-1}\ Mpc^{-1}}$ when using theLMC distance, Milky Way parallaxes and the NGC~4258 megamaser as the Cepheidzeropoint, and $68.8\pm 3.3\ \mathrm{km\ s^{-1}\ Mpc^{-1}}$ when only usingNGC~4258. Our correction brings the direct measurement of $H_0$ within $\sim1\,\sigma$ of recent indirect measurements based on the CMB power spectrum.

Confirmation of a Star Formation Bias in Type Ia Supernova Distances and its Effect on Measurement of the Hubble Constant