Dunque, oggi è domenica e so che vi aspettereste i soliti raffronti numerici, ma è successa una cosa che merita di essere raccontata.
Alcune settimane fa sono stato intervistato dall’autore di un podcast a carattere scientifico che va in onda in Nuova Zelanda; come sempre quando parlo di nucleare e fornisco numeri e statistiche, ho invitato il mio intervistatore e il suo pubblico a verificare indipendentemente presso le fonti più accreditate la veridicità delle mie affermazioni.
Il mio intervistatore mi ha preso in parola, e ha mandato una mail alla Chernobyl Tissue Bank, per avere un riscontro circa i dati che avevo snocciolato sull’incidente nucleare del 1986.
La Chernobyl Tissue Bank è un progetto dell’Organizzazione Mondiale della Sanità, che raccoglie dati ed effettua studi sulle conseguenze dell’incidente di Chernobyl dal 1998. Al progetto collaborano i maggiori esperti internazionali di radioprotezione e i dati della Chernobyl Tissue Bank vengono costantemente utilizzati come riferimento in altri importanti studi di caratura internazionale.
Per farla breve, si tratta della fonte scientifica più importante al mondo su questo tema.
Bene, la risposta della Chernobyl Tissue Bank è arrivata ieri, firmata dalla direttrice Gerry Thomas in persona, confermando che quello che avevo detto nell’intervista, che è esattamente ciò che avevo scritto anche nei miei post di domenica scorsa, è assolutamente corretto: il conto dei morti passati, presenti e futuri attribuibili all’incidente di Chernobyl è di alcune centinaia, con la stima più probabile che non supera le 200 unità.
Questi sono i dati scientifici.
Il resto è fuffa giornalistica o terrorismo psicologico.
Qui lo scambio di mail, per chi capisce l’inglese (per la privacy ai nomi sono state sostituite le iniziali).
“Hello Chernobyl Tissue Bank,
My name is H.B., I am working on an environmental project looking at Nuclear Power as a safe alternative for power generation.
I was talking to a nuclear scientist who said the casualty rate of Chernobyl is generally blown out of proportion. The Chernobyl Tissue Bank, being the most reliable source, should have the answers.
Would be able to answer some basic questions for me?
1. How many people died within the first few months of the Chernobyl meltdown (Immediate or near immediate deaths)?
2. How many people have died in the years up until now, that can have their deaths directly linked to the Chernobyl meltdown?
3. What is the current prediction of deaths which may occur in the future as a direct link to the Chernobyl meltdown?
4. If I add all of these numbers together, would you say this is an accurate representation of the human toll caused by the Chernobyl meltdown, ignoring injury and mental anguish etc.?
Thank you for your time and consideration.
Sorry for the delay in responding. I’ll answer your questions in turn.
How many people died within the first few months of the Chernobyl meltdown (Immediate or near immediate deaths)?
3 people died in the accident itself – one from a heart attack, one from thermal burns and another is believed to still be buried somewhere in the rubble. 143 people were diagnosed with acute radiation syndrome (ARS) (they received doses of over 1 Sv); 28 of these died as a result of a combination of ARS and thermal burns. 19 of this cohort have died subsequently, but it is difficult to attribute death by alcohol, smoking or a traffic accident to exposure to radiation.
How many people have died in the years up until now, that can have their deaths directly linked to the Chernobyl meltdown?
There have been 19 deaths from thyroid cancer in about 10 million children (i.e. aged under 19 at the time of the accident) who were exposed to 131-I in fallout. There have been around 20,000 cases of thyroid cancer, 5000 of which are attributable to the radiation, according to UNSCEAR, but the mortality rate from thyroid cancer is about 1% over around 50 years. This is why the number of deaths is so low – thyroid cancer is the only cancer to have increased in the population and only in those who were children or adolescents at the time of the accident. This was not unexpected – it is known from animal studies that if you give radioiodine when the thyroid is growing, you increase the chance of thyroid cancer occurring later in life. We also know from a lot of human studies that when the thyroid stops growing (around the age of 20 in man) that radioiodine exposure no longer causes an increase in thyroid cancer risk. Thyroid cancer is very rare in the young normally, but does increase in incidence as we age – and some studies suggest that about 50% of the population may have a thyroid cancer that is subclinical at death. It is the sort of cancer that you live with, not die from, unless you are extremely unlucky!
What is the current prediction of deaths which may occur in the future as a direct link to the Chernobyl meltdown?
It has been estimated that over a 50 year period exposure to radioiodine will have caused an excess of 16000 thyroid cancers in the population – that would give an estimated final death toll of 160 cases. The cohorts of liquidators are being followed up – it was estimated in 2006 that there may be 4000 excess cases of cancer in this cohort, based on the individual doses of radiation these workers received. However, none of the studies carried out on these cohorts have yet shown an increase in cancer of any sort, which suggests that this may be an overestimate. Please note that what is quoted is cancer cases, not cancer deaths. This is often misquoted as cancer deaths in the media – because cancer is becoming ever more curable, we cannot estimate cancer deaths, as treatments become better over time. If the radiation does not result in a significant increase in cancer cases in this cohort, then the effect on the population at large will also be much smaller than expected. The original estimates of 1000s of extra cancer cases comes from the use of a now outdated method called the cumulative dose, which was a bit like saying if 1 million men cut themselves shaving every day and lose 1ml of blood = 1000 litres of total blood loss. If you lose 2.5 litres of blood you are likely to die, therefore 400 men will die from shaving that day (1000/2.5). The collective dose has been dismissed now as an accurate way of estimating cancer cases – and you can see from the analogy why it is a stupid way to calculate possible cancer cases.
If I add all of these numbers together, would you say this is an accurate representation of the human toll caused by the Chernobyl meltdown, ignoring injury and mental anguish etc.?
It is difficult to give a definitive estimate, but my reasoning is this – 31 deaths from the accident itself (3 from the accident and 28 deaths from ARS), an expected 160 (1% of 16,000) thyroid cancer deaths. This totals less than 200, but you probably need to add a few deaths in the liquidator cohort, although whether these can be accurately attributed to radiation exposure is a different matter. I would say anywhere between 200 – 500, and my expectation would be the lower end of this. People expect the toll to be higher because they think the individual doses were much higher than they were, and because they don’t understand that under 100 mSv it becomes very difficult to really be sure that radiation does anything – your chances of dying from other causes are much greater than the chances of dying from the radiation.
I would recommend that you read the Oxford Martin restatement on radiation (https://www.oxfordmartin.ox.ac.uk/…/oxford-martin…/). This will give you a lot more information.