Toxicology of Industrial Compounds

‘out of the blue’, in an individual that would otherwise have a low cancer
risk. It ‘only’ reduces the individual’s tumour-free lifetime.
No cancer ‘out of the blue’
W.K.LUTZ 359
Figure 25.1 Schematic representation of the time course of tumour appearance in a
group of individuals with large differences in susceptibility. Solid line: background
process of spontaneous carcinogenesis; arrows: acceleration of the spontaneous
process by exposure to an additional carcinogen.
This interpretation does not contradict the understanding that a low dose of
a carcinogen could increase the tumour incidence from 40000 to 40001 per
1000000 lives, in the example shown in Table 25.1. The connection
between the two approaches is shown in Figure 25.1. The solid line shows
the appearance of a spontaneous tumour in individuals of a group of 20
people. At the age of 65 years, 4 individuals have a tumour diagnosed. This
is equivalent to a cumulative tumour incidence of 20 per cent. Exposure of
this group to an additional exogenous carcinogen would result in some
reduction in the tumour-free lifespan in all individuals. In the example
shown in Figure 25.1, this shift would move one additional individual to
an age of diagnosis