SUMMARY Several c a t a l y t i c t r i t i u m exchange procedures have been i n v e s t i g a t e d i n o r d e r t o accomplish u n i f o r m and random i n c o r p o r a t i o n o f t r i t i u m i n t o t h eti Formerly:Address correspondence and r e p r i n t requests t o DSF o r JRJ.

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After that these theoretical parametrs were related to the activity carcinogenity of these compounds as carcinogenic agents. The results showed that two factors can be related to carcinogenity of these compounds; the first one is the carbon atoms of low electron densities (i.e the position of electrophilic atoms), the second is the hardness of these compounds.We have also used electron density to highlight the possible strengths of interactions of PAHs with DNA of living cells. On the bases that the main metabolic pathway for activation of these compounds involves formation of bay-region diol epoxide, then, the benzylic carbocations generated from these electrophilic diol epoxide by opening of the epoxide ring are capable of forming covalent adducts with the nucleophilic site in DNA which represent the main factors of carcinogenity of these compounds since adduct is accepted as a critical step in the mechanism by which (PAHs) can cause a genetic mutation resulting inductions of cancer.