Charged particles such as electrons and quarks are not allowed to have a hard Majorana mass (see here). With 'hard' I mean an explicit mass term in the Lagrangian which would break the corresponding symmetries. However, there are also mechanisms to effectively generate masses, for example, with instantons in the topologically non-trivial QCD vacuum ('t Hooft vertex / determinant). These mass terms do not explicitly arise in the Lagrangian, only occur due to the specific vacuum the Lagrangian 'chooses' and are thus not forbidden by symmetries.
Now my question is: are there any experimental bounds on Majorana masses for charged particles?