Cancer risk from chronic exposures to chemicals and radiation: a comparison of the toxicological reference value with the radiation detriment

Abstract

This article aims at comparing reference methods for the assessment of cancer risk from exposure to genotoxic carcinogen chemical substances and to ionizing radiation. For chemicals, cancer potency is expressed as a toxicological reference value (TRV) based on the most sensitive type of cancer generally observed in animal experiments of oral or inhalation exposure. A dose-response curve is established by modelling experimental data adjusted to apply to human exposure. This leads to a point of departure from which the TRV is derived as the slope of a linear extrapolation to zero dose. Human lifetime cancer risk can then be assessed as the product of dose by TRV and it is generally considered to be tolerable in a 10 -6 -10 -4 range for public in normal situation. Radiation exposure is assessed as effective dose corresponding to a weighted average of energy deposition in body organs. Cancer risk models were derived from the epidemiological follow-up of atomic bombing survivors. Considering a linear-no-threshold dose-risk relationship and average baseline risks, lifetime nominal risk coefficients were established for 13 types of cancers. Those are adjusted according to the severity of each cancer type and combined into an overall indicator denominated radiation detriment. Exposure to radiation is subject to dose limits proscribing unacceptable health detriment. The differences between chemical and radiological cancer risk assessments are discussed and concern data sources, extrapolation to low doses, definition of dose, considered health effects and level of conservatism. These differences should not be an insuperable impediment to the comparison of TRVs with radiation risk, thus opportunities exist to bring closer the two types of risk assessment.

The scientific basis for the use of the linear no-threshold (LNT) model at low doses and dose rates in radiological protection

“…Regarding methodology, the use of human data is to be favoured for constructing these values. However, unlike for ionising radiation, support studies have mainly been experimental studies on animals and continue to remain so for the regulatory evaluation of new chemical substances (Cléro et al 2021). This trend is changing.…”

“…There are some similarities between the TRV used for chemical substances and the detriment used for radiation, but also differences, which justify being prudent when comparing the two approaches. In particular, it is the critical effect (effect corresponding to an adverse effect, specific to the substance and occurring at the lowest doses or concentrations in the most vulnerable population) that is used to establish the corresponding TRV, whereas a cumulative approach (sum of cancer risks for a set of organs) is used in radiological protection to calculate the radiological detriment (Cléro et al 2021).…”

Risk-Reducing Measures for Cancer Prevention

“…Importantly, using sunscreen as a mitigation measure for a longer stay in the sun is counterproductive [ 40 ]. Adhering to all safety measures and precautions in the use of radiation-generating materials and devices, both in hospital settings and various workplaces is important to reduce the risk of skin cancer [ 1 , 41 ].…”

“…40) Adhering to all safety measures and precautions in the use of radiation-generating materials and devices, both in hospital settings and various workplaces is important to reduce the risk of skin cancer. 1,41)…”

On harmonization of health risk indicators caused by ionizing radiation exposure and other harmful factors based on DALY estimates

“…Given that, issues related to harmonizing approaches to assessment of ra-diation risks and other health risks arise quite frequently and discussed independently [1,2]. In addition, recently it has often been noted that it is necessary to revise the assessment methodology and measures of radiation health risks that are currently applied [3][4][5][6]. When tackling multiple issues related to public healthcare organization and population health assessment, the expert society more and more often suggest a gradual transition from mortality-based health measures to more informative summary health measures based on calculating how many years of healthy life have been lost due to disease, disability or injury, that is, number of lost healthy life years without any limitations on activity, functionality, and working capacities [7,8].…”