Speaker
Description
The paper raised specific concerns about the use of quantities and units in assessing radiation risk from both low-level and high-level exposures, which can result in stochastic or deterministic health effects. The focus is on cases where the exposure quantification does not entirely align with the recommendations of international scientific radiation protection commissions and committees. These inconsistencies were also evident in some scientific publications and spread among radiation workers, causing some confusion. Stochastic radiation effects are health issues, primarily cancer and genetic effects, that occur by chance at any dose. The probability of the effect increases with the absorbed dose, but the severity of the effect does not change. Unlike deterministic effects, which only appear above a certain dose threshold and worsen with dose, stochastic effects have no minimum threshold and can manifest years after exposure, often with a long latency period. The probability of stochastic effects occurring is typically proportional to the dose received. Stochastic effects after radiation exposure occur many years later (the latent period). The severity is independent of the dose originally received. On the other hand, deterministic effects are caused by severe cell damage or death. Individuals who experience the physical effects of this cell death do so when it is large enough to cause significant tissue or organ impairment. These effects are short-term, adverse tissue reactions resulting from a dose that is significantly high enough to damage living tissues. The severity of a deterministic effect increases with radiation dose above a threshold, below which the detectable tissue reactions are not observed. Deterministic effects are usually predictable and reproducible. For example, localized doses to certain parts of the body at increasing levels will result in well-understood biological effects. Quantifying radiation health effects is challenging because deterministic effects have dose thresholds, varying severity, and predictable outcomes, while stochastic effects lack a dose threshold, are probabilistic, and their severity is independent of dose. Specific problems include accurately assessing the risk from low-dose exposures, differentiating radiation-induced diseases from naturally occurring ones, establishing accurate dose response relationships, and accounting for individual variability in sensitivity and repair mechanisms. Although radiation effects at low exposure should be quantified in the unit Sv, this unit is often incorrectly used for estimating deterministic effects. Just two examples may illustrate this still quite frequently occurring mistake. The difficulties in quantifying the health effects of radiation are primarily due to the fact that we have more than ten quantities for assessing stochastic effects and only one for evaluating deterministic effects. Moreover, although all these quantities are supposed to replicate both irradiation conditions, i.e., external and internal exposures, there are still difficulties in expressing the health effects produced by mixed exposure (external and internal). It looks like the future development will be moving towards having two kinds of quantities: a) a minimal number of quantities specially introduced for monitoring purposes, and b) more sophisticated quantities for research applications.
| Preferovaná sekcia | Biologické účinky žiarenia a odhad rizika z ožiarenia |
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