We consider the case of sudden sodium layers which have been reported in the lower E region of the ionosphere. We suggest that dissociative electron attachment to NaHCO3, NaHCO3+e→Na+HCO3-, can explain some of the observations, in particular at altitudes above 95 km. This process would produce Na efficiently only in the case where a plasma of high density is injected into the sodium layer. The rate constant for the reaction is estimated to be of the order of 10-8 cm3 s-1 by analogy with similar species and by derivation from the observed geophysical parameters. ¿ American Geophysical Union 1990