Do neutrino rest masses affect cosmological helium production?

It is shown that the possibility of nonzero neutrino rest masses mν 10 eV/c2 does not alter previous predictions of the standard big-bang model for the primordial He4 abundance. Although both left- and right-handed neutrinos could then be present, reactions mediated by the standard Weinberg-Salam-Glashow model extended to include Dirac neutrinos with nonzero rest mass cannot maintain νR in thermal equilibrium.