According to the evaluations made by IARC, 66 agents or exposures have been recognised as human carcinogens.

About 60% of all cancer cases occur in people over 65 years of age, which is indeed the most important risk factor for cancer, including both the duration of exposure to the variety of carcinogenic agents and allowing expression of genetically determined disorders.

Diet as a source of mutagens as well as other environmental mutagens may affect blood pressure either directly or by favouring the development of arteriosclerosis : mutagens have been shown to accelerate arteriosclerotic plaque development.

Some concern has also been expressed on the possible adverse effect that environmental chemicals may have on reproductive ability, on the basis of the decline in semen quality reported over the past decades.

Better defining the role of aetiological agents would result in a more precise definition of attributable risks.

Of particular interest to the latter goal are the studies of inter-individual variability in the susceptibility to carcinogens, which will hopefully contribute to define the role of low-level exposure to carcinogens.