Lack of Correlation between Stem-Cell Proliferation and Radiation- or Smoking-Associated Cancer Risk.

Background: A recent paper by Tomasetti and Vogelstein (Science 2015 347 78-81) suggested that the variation in natural cancer risk was largely explained by the total number of stem-cell divisions, and that most cancers arose by chance. They proposed an extra-risk score as way of distinguishing the effects of the stochastic, replicative component of cancer risk from other causative factors, specifically those due to the external environment and inherited mutations.

Objectives: We tested the hypothesis raised by Tomasetti and Vogelstein by assessing the degree of correlation of stem cell divisions and their extra-risk score with radiation- and tobacco-associated cancer risk.

An empirical method for deriving RBE values associated with electrons, photons and radionuclides.

There is substantial evidence to justify using relative biological effectiveness (RBE) values of >1 for low-energy electrons and photons. But, in the field of radiation protection, radiation associated with low linear energy transfer has been assigned a radiation weighting factor wR of 1. This value may be suitable for radiation protection but, for risk considerations, it is important to evaluate the potential elevated biological effectiveness of radiation to improve the quality of risk estimates.

Perspective on the use of LNT for radiation protection and risk assessment by the U.S. Environmental Protection Agency.

The U.S. Environmental Protection Agency (EPA) bases its risk assessments, regulatory limits, and nonregulatory guidelines for population exposures to low level ionizing radiation on the linear no-threshold (LNT) hypothesis, which assumes that the risk of cancer due to a low dose exposure is proportional to dose, with no threshold.

What can epidemiology tell us about risks at low doses?

Puskin, J. S. What Can Epidemiology Tell Us about Risks at Low Doses? Radiat.

Radon exposure assessment and dosimetry applied to epidemiology and risk estimation.

Epidemiological studies of underground miners provide the primary basis for radon risk estimates for indoor exposures as well as mine exposures. A major source of uncertainty in these risk estimates is the uncertainty in radon progeny exposure estimates for the miners. Often the exposure information is very incomplete, and exposure estimation must rely on interpolations, extrapolations and reconstruction of mining conditions decades before, which might differ markedly from those in more recent times.

The U.S. Environmental Protection Agency's assessment of risks from indoor radon.

The U.S. Environmental Protection Agency has updated its assessment of health risks from indoor radon, which has been determined to be the second leading cause of lung cancer after cigarette smoking.

Cancer risks attributable to low doses of ionizing radiation: assessing what we really know.

High doses of ionizing radiation clearly produce deleterious consequences in humans, including, but not exclusively, cancer induction. At very low radiation doses the situation is much less clear, but the risks of low-dose radiation are of societal importance in relation to issues as varied as screening tests for cancer, the future of nuclear power, occupational radiation exposure, frequent-flyer risks, manned space exploration, and radiological terrorism. We review the difficulties involved in quantifying the risks of low-dose radiation and address two specific questions.

Smoking as a confounder in ecologic correlations of cancer mortality rates with average county radon levels.

Cohen has reported a negative correlation between lung cancer mortality and average radon levels by county. In this paper, the correlation of U.S.

Estimates of radiogenic cancer risks.

A methodology recently developed by the U.S. EPA for estimating the carcinogenic risks from ionizing radiation is described.

Bone cancer risk estimates.

Due to confusion between endosteal (bone surface) dose and average skeletal dose, ICRP 60 has substantially overestimated the risk of radiogenic bone cancer. This confusion apparently stems from an incorrect reading of the BEIR IV report, which does not clearly draw this distinction. It should also be noted that what appear to be summary numerical risk estimates for bone sarcoma induction in BEIR IV and BEIR V refer only to average skeletal dose as calculated for 224Ra.

An analysis of the uncertainties in estimates of radon-induced lung cancer.

A recent report by the National Academy of Sciences estimates that the radiation dose to the bronchial epithelium, per working level month (WLM) of radon daughter exposure, is about 30% lower for residential exposures than for exposures received in underground mines. Adjusting the previously published BEIR IV radon risk model accordingly, the unit risk for indoor exposures of the general population is about 2.2 x 10(-4) lung cancer deaths (lcd)/WLM.

EPA's perspective on risks from residential radon exposure.

Indoor radon has been judged to be the most serious environmental carcinogen which the EPA must address for the general public. The optimal strategy for dealing with this problem depends on the magnitude of the risk, how the risk is distributed within the population, as well as the effectiveness and costs of mitigation measures. Based on current exposure and risk estimates, radon exposure in single-family houses may be a causal factor in roughly 20,000 lung cancer fatalities per year.

A retrospective look at Rn-induced lung cancer mortality from the viewpoint of a relative risk model.

The potential contribution to U.S. lung cancer deaths from 1930 to 1987 from indoor 222Rn exposures is investigated from the standpoint of a constant relative risk model.