The theoretical analysis of the environmental effects during beta decay is associated with the solution of a multiparticle problem in quantum mechanics. In the general case, we should take into account effects arising from the changing nuclear charge as well as the electromagnetic interaction of the beta particle with the atomic electron. In this paper, we consider beta decay in the simplest atomic structure-the tritium atom, and calculate both adiabatic and nonadiabatic corrections to the traditional beta decay theory. The results of these calculations have a significant bearing on the extraction of neutrino mass from very accurate measurements of the beta spectrum of tritium.