The
impacts of the Chernobyl nuclear disaster in 1986
included thyroid cancers in those who were children at the time. The United Nations Scientific Committee on the Effects
of Atomic Radiation (UNSCEAR) produced a report in 2008 which found that,
among those exposed who had been under 14 years of age in 1986, there were
5,127 reported cases of thyroid cancer between 1991 and 2005, while, for those
who had been under the age of 18 in 1986, there were 6,848 cases. The main
exposure route is assumed to be from drinking milk contaminated with radioactive fallout.
Thyroid cancer can be treated
e.g. by surgical removal of the thyroid (with patients then having to take
compensatory pills for rest of their lives), but even so, fifteen cases had
proved fatal by 2005. More are possible later. Thyroid cancer can occur
naturally, but UNCEAR accepted that the observed pattern of dramatically
increased thyroid cancer in the initial period 1991-1995 was associated with
the accident. The typical minimum latency
period for thyroid cancers is around 5 years, so it might be hoped that,
sometime after that, cases would gradually tail off, but, worryingly, UNCEAR
found no evidence for a decrease in the annual excess incidence of thyroid
cancer up to 2005- the end of the observation period for the report. However,
for those born after 1986, there was no evidence for an increase in the annual
incidence of thyroid cancer. On that basis it might be assumed that new
exposures or effects were not occurring, but that the latency period for
cancers amongst those exposed in 1986 was extending. That cohort might also be
joined by those who were in utero at
the time.
There have been follow up
studies and reviews and they have produced some worrying conclusions, outlined
in a new UNSCEAR report. It notes that ‘the
total number of cases of thyroid cancer registered in the period 1991−2015 in
males and females, who were under 18 in 1986 (for the whole of Belarus and
Ukraine, and for the four most contaminated oblasts of the Russian Federation),
approached 20,000. This number is almost three times higher than the number of
thyroid cancer cases registered in the same cohort in the period 1991−2005’.
So it’s going up
significantly- with females especially at risk. UNSCEAR says ‘on average, the registered numbers of
thyroid cancer for females were about four times higher than for males’. Not
all of these cases will have been due to radiation exposure. UNSCEAR says other
factors include ‘an increased spontaneous incidence rate with
adulthood…and improvement in diagnostic methods’. So they claim that ‘the fraction of the thyroid cancer cases in the period 2001-2008
attributable to the radiation exposure caused by the accident is assessed to be
about 0.6 and 0.25 for the evacuated and non-evacuated children and
adolescents, respectively’. Even so, that’s nearly 12,000 cases for those
in the zone, 1 in 4 for the rest. Although
UNSCEAR note that ‘the uncertainty range
of the estimated attributable fraction extends at least from 0.07 to 0.5’. They
call for more research. https://news.un.org/en/story/2018/04/1008292
Full report: www.unscear.org/unscear/en/publications/Chernobyl_WP2017.html
Thyroid cancer was only one the impacts of the radiation
release at Chernobyl, and children were not the only victims. As well as the
rest of the population, many thousands of clean up workers were also exposed, some
to high levels, and, although many have died, death was not the only outcome- for
them or the others, there were also illnesses later in life that may not always
have been linked back to radiation exposure, including immune system
degradation: http://static1.1.sqspcdn.com/static/f/356082/27889370/1524233076657/Thunderbird_BeyondNuclear_Chernobyl_April2018.pdf
However, the likely long-term health impacts of what
happened at Chernobyl (and Fukushima) are still debated: https://ourworldindata.org/what-was-the-death-toll-from-chernobyl-and-fukushima It’s a contentious area. But the new UNSCEAR study may dent some of the
more complacent/official views, for example see: www.jaif.or.jp/ja/annual/46th/46-s3_gerry-thomas_e.pdf
Certainly more research is needed, as UNSCEAR says. Its
selection of 0.6 and 0.25 as the radiation-related proportion seems debatable- why
so low? Also it’s not clear exactly what is happening to the post-Chernobyl
population. Is the rise in cancers due
to new exposures? The half life of Caesium
137 is around 30 years, so the activity level of any that remains in the
ecosystem should be about 50% less by now and continually falling – so the cancer
rate should be falling too, not increasing. More likely is a delayed onset
effect from the initial exposures.
The administration of iodide pills, to block radioactive Iodine-131 uptake in the thyroid, would have limited the risk, but evidently did not
happen much or in time. So now we await the long term results. Fortunately, 25
years later, most children in the Fukushima
area seem to have escaped these problems: iodate pills were distributed –
though they have to be taken very promptly, and that may not have always
happened in the post-accident chaos there. Tragically, once more, we will have
to wait to see- although some increases have already been claimed: http://bigstory.ap.org/article/9bd0b3e588634b908193939638126250/researcher-childrens-cancer-linked-fukushima-radiation
It will take time to know for certain. Some say that you
can worry too much about radiation exposure: we are already exposed to natural background
radiation and to X-rays used for medical purposes. Major nuclear accidents expose some people,
usually reactor staff and firefighters, to massive doses of radiation, which
can kill outright- 30 or more people
died soon after Chernobyl. However, it’s the longer-term risk of absorbing/ingesting/breathing
in radio-nuclides that’s the key worry- including isotopes that don’t exist in
nature. Once internalized, and if
lodged somewhere in your body, the active particles can continue to irradiate
cells intensively for very long periods. That’s not the same as exposure to low
level background external radiation, or to short exposures from external
sources like X-rays, or even to ‘prompt’ radiation fluxes from reactor
accidents (or nuclear explosions), if you are some way away. The extra
exposures from nuclear plants, including routine and accidental releases, averaged across the wider public over time,
can seem small in some cases, but it does all add up, and we need to minimise total
exposures, and certainly any internalisation. Especially since it’s not always averaged out: leaks and
accidents at nuclear plants can expose many local people to large extra doses,
with, as we have seen, uncertain long term results. It is, arguably, not a risk
worth taking. So, it could
be argued that the best protection in future is not iodate pills, masks or
evacuation. It’s to avoid the use of these plants- and to go for renewables
instead. A small local start: www.bbc.co.uk/news/av/world-europe-43929480/solar-plant-built-at-site-of-chernobyl-nuclear-disaster
All technologies have health and safety risks, but those
associated with the renewables (large hydro dam failures apart) are generally
small and local (e.g. a total so far of around 180 wind turbine-related
occupational fatalities, mostly from installation accidents) compared with
those of nuclear and (especially) the burning of fossil fuels due to air
pollution and climate change. Whatever we do now, there will be long-terms
impacts from our past use of fossil and nuclear fuel, but, in both cases, we
can avoid further use. These days we tend to focus on avoiding climate change
and fossil fuel, but those tempted to see nuclear as an answer need to be
reminded of what can go wrong- it can have wide ranging human costs and leave a
long lived, brutal legacy: www.theguardian.com/commentisfree/2019/apr/04/chernobyl-nuclear-power-climate-change-health-radioactivity
New
books on Chernobyl: www.nybooks.com/articles/2019/04/04/chernobyl-syndrome/
A movie: www.independent.co.uk/arts-entertainment/tv/news/chernobyl-trailer-video-hbo-sky-atlantic-drama-nuclear-disaster-cast-a8845216.html
The next post in this series will be on
nuclear fusion- maybe not whole lot better.
