Abstract
Radiation and Cancer
Since the publication of the UNSCEAR 2000 Report, more information has become available from epidemiological studies of radiation-exposed populations.
There have been updates to the follow-up of RERF Life Span Study (LSS), both for solid cancer incidence and all cancer mortality. The analysis using the new DS02 indicate that cancer risk might decrease by about 8%, with no appreciable change in the shape of the dose response or in the age-time patterns of excess risks.
New findings have also been published from analyses of fractionated or chronic low-dose exposure, in particular the IARC 15-country nuclear worker study, and analyses of the Techa River and Semipalatinsk datasets. However, there are concerns about bias involved in all above three studies.
Cancer risks have been assessed for 24 different cancer sites in the report. There are cancers for which there is little evidence for an association with radiation (e.g. pancreatic cancer, melanoma of skin, prostate cancer, non-Hodgkin' s lymphoma, Hodgkin' s disease, multiple myeloma), and others where excess risks have only been seen following very high dose exposures (e.g. cancers of the small intestine, rectum, uterus, kidney).
The new results of LSS is again consistent with a linear dose-response for the risk of all solid cancers combined; therefore, as a first approximation, linear extrapolation can be used for estimating solid cancer risks at lower doses.
Radiation and Non-cancer Disease
There is an evidence of increased risk of cardiovascular disease (CVD) associated with high dose radiation to the heart delivered by radiotherapy. However to date, the evidence for an association between fatal CVD and radiation doses in the range of less than 1-2 Gy comes only from the analysis of LSS. Other studies have not provided clear or consistent evidence of a fatal CVD risk. It is the conclusion of the Committee that, given the inconsistent epidemiological data and the lack of a biologically plausible mechanism, the present scientific data are not sufficient to establish a causal relationship between ionizing radiation and CVD at doses less than 1-2 Gy.
