The main shortcoming in this draft is that it does not enough take into account new scientific data and their potential implications.
The 100 mSv figure
In paragraph 22, it is said that there is reliable scientific evidence that whole-body exposures on the order of ≥100 mSv can increase the probability of cancer occurring in an exposed population and that below 100 mSv, the evidence is less clear. The draft adds that ICRP prudently assumes, for purposes of radiological protection, that even small doses might result in a slight increase in risk. References to this level of 100 mSv can be found at several places throughout the draft. There is currently of lot of strong and reliable epidemiological and radiobiological indications of effects below 100 mSv. Therefore, protecting people below 100 mSv is currently not only a question of “prudence” but rests on a solid scientific basis. In addition, experience has shown that the use of this 100 mSv figure is frequently and wrongly understood as a kind of threshold between safe and non-safe.
New data about non-cancer radiation-induced effects
In 2017, a EU Scientific Seminar (EU Scientific Seminars are devoted every year to emerging issues in Radiation Protection, addressing new research findings with potential policy and/or regulatory implications) was devoted to “Emerging issues with regard to organ doses” (Radiation Protection n°187, European Commission, Luxembourg, 2018, available at https://ec.europa.eu/energy/en/radiation-protection-publications).
From the presentations and discussions, some important issues were highlighted.
Radiation-induced effects on the brain, the cardiovascular system and the lens of the eye have now been observed below the currently assumed threshold of 500 mSv (as assumed in paragraph 19 of the ICRP draft). Clear radiation-induced health effects are already observed at intermediate doses of 100 to 500 mSv and, as these effects present a cumulative character, lifetime or cumulative dose limitations should be introduced (workers, people living in long-term contaminated areas). In some cases (particularly the brain for pre- and post-natal exposures), effects are already observed at lower doses in the order of a few tens of mSv. In order to increase the statistical power and to have more dosimetric and biological data allowing to understand the mechanisms of the cognitive and cerebrovascular effects after an exposure to low ionizing radiation doses, the project CEREBRAD was developed and supported by the EU Euratom 7th framework programme (FP7) with a multidisciplinary approach (human epidemiology, animal studies and mechanistic studies). This project unveiled effects at doses previously assumed to be harmless. Persistent effects (DNA damages, inflammation) were observed in animal studies at low doses (20 and 100 mGy) several months after exposure (corresponding to years in humans) (Benotmane A., in EU 2018). Combined exposures to radiation and other environmental agents decreased significantly the dose at which brain effects are observed (Eriksson et al., 2010). Interestingly, compared to the offspring exposed to maternal alcohol intake or to infectious agents (zika virus (ZIKV)), the neuropsychological development and the transcriptomic modifications of those prenatally exposed to ionising radiation are highly similar, including induction of genes involved in premature neuron differentiation (Benotmane A., in EU 2018).
As highlighted in the EU 2018 scientific seminar (in press) devoted to “Epigenetic effects: potential impact on radiation protection”, alterations of epigenetic mechanisms play a role in late radiation-induced brain effects after prenatal and early post-natal irradiation. A critical moment occurs in the very beginning of pregnancy (first days) when genome-wide global demethylation occurs followed by progressive developmental epigenetic programming that is crucial for normal brain maturation. These processes are vulnerable to early life stresses, including ionizing radiation, maternal stress, toxicological exposures, and viral infections.
Both EU seminars concluded that, although many uncertainties exist, the current knowledge is nevertheless sufficient for taking into account the risk of such effects in radiotherapy, interventional radiology and cardiology, pediatric radiology (CT) and in accidental situations, and this particularly for vulnerable groups such as embryos and foetus (pregnant women) and small children.
Benotmane A, Cognitive and cerebrovascular effects induced by low dose ionizing radiation: CEREBRAD, in EU Scientific Seminar May 2017: Emerging issues with regard to organ doses. Radiation Protection n°187, European Commission, Luxembourg, 2018
Eriksson P., C. Fischer, B. Stenerlow, A. Fredriksson, S. Sundell-Bergman, Interaction of gamma-radiation and methyl mercury during a critical phase of neonatal brain development in mice exacerbates developmental neurobehavioural effects, Neurotoxicology 31(2) (2010) 223-9.
Protection of infants, children and pregnant women
in the light of these new data, measures of protection of pregnant women, infants and children in the various phases of accidental situations should be re-evaluated, including specific lower reference levels (reference levels for restricting emergency exposures, reference level for people living in long-term contaminated areas). In this respect, the introduction of a new reference level at 10 mSv/y for people living in long-term contaminated areas is certainly welcome, although this reference level is not specific to vulnerable groups and is again based on a supposed 100 mSv threshold (“annual exposures of the order of 10 mSv during the first years of the recovery process, added to exposure received during the emergency response, could lead to total exposures greater than 100 mSv in a relatively short period of time for some affected people”). Anyway, this new reference level at 10 mSv/y should be accompanied by other reference levels for the cumulated doses over the years.
Globally, protection of pregnant women, infants and children is not enough highlighted in the ICRP draft and there are only a very limited number of paragraphs and recommendations concerning these vulnerable groups, although there are a lot of scientific data justifying specific protection provisions for them and while this is a major concern for the population.