Comparative Carcinogenicity of Ionizing Radiation and Chemicals

NCRP has published an evaluation of the extent to which principles and methods that have been developed for use in assessing 

The carcinogenic effects of certain chemicals in man and laboratory animals are similar to those of ionizing radiation. 

Cancers induced by ionizing radiation and chemicals are individually indistinguishable from those of the same type induced by other causes. Thus, in either case, induction of cancers can only be inferred from statistical analyses of a dose-dependent increase in their frequency in exposed populations. 

From studies of human populations exposed to certain chemicals, available data are sufficient to characterize the dose-incidence relationships for some types of cancer at high dose levels. However, as in the case of ionizing radiation, the data are not sufficient to define the dose-incidence relationships precisely for any form of cancer over a wide range of doses and dose rates. Therefore, the probability of cancer induction that may be associated with low doses of chemicals that would be of primary concern in protection of public health can be estimated only by interpolation and extrapolation of data at higher doses and dose rates, based on assumptions about the dose-incidence relationships and mechanisms of toxicity. For the few chemicals for which incidence data are available over a range of doses, the dose-incidence relationship is not inconsistent with linearity, but this result does not constitute proof of linearity. 

Few chemicals identified as carcinogens in laboratory animals are known to cause cancer in humans, and the dose to affected tissues for these chemicals usually is not known well enough to define the dose-response relationship except in a general way. In this respect, the carcinogenic effects of most chemicals in humans are far less well known than are those of ionizing radiation. 

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National Council on Radiation Protection and Measurem its. Comparative Carcinogenicity of Ionizing Radiation and Chemicals. 

NCRP (1989). National Council on Radiation Protection and Measurements. Comparative Carcinogenicity of Ionizing Radiation and Chemicals, NCRP Report No. 96 (National Council on Radiation Protection and Measurements, Bethesda, Maryland). 

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