Skupina C - středně toxické:
C14, N16, Na22, Na24, Si31, P32, S35, Cl36, K42, Ca47, Sc46, Sc47, Sc48,
V48, Mn52, Mn54, Mn56, Fe55, Co58, Co60, Ni59, Ni63, Ni65, Cu64, Zn65,
Zn69m, Ga72, As73, As74, As76, As77, Se75, Br82, Kr87, Kr88, Rb86, Rb88,
Sr85, Sr89, Sr91, Sr92, Y91, Y92, Y93, Zr93 + No93, Zr95 + Nb95, Mo99,
Tc96, Tc97m, Tc97, Tc99, Ru103, Ru105, Rh105, Pd103 + Rh103, Pd109, Ag105,
Ag111, Cd109 + Ag109, Cd115, Cd115m, In114m, Sn113, Sb122, Sb124, Sb125,
Te125m, Te127m, Te127, Te129m, Te129, Te132, I132, I133, I134, I135, Cs135,
Cs136, Cs137 + Ba137, Ba131, Ce141, Ce143, Pr142, Pr143, Nd146, Nd149,
Pm147, Pm149, Sm153, Eu152m, Eu155, Gd153, Gd159, Tb160, Dy166, Ho166,
Er169, Er171, Tu171, Yb175, Lu177, Hf181, Ta182, W181, W185, W187, Re183,
Re186, Re188, Os191, Os193, Ir190, Ir192, Ir194, Pt191, Pt193, Pt197,
Au196, Au198, Au199, Hg197m, Hg197, Hg203, Te200, Te202, Te204, Pb203,
Pb212, Bi206, Th231, Pa233, U240.