Just as climate-change deniers leap from scientific uncertainty over the precise impacts of greenhouse gas emissions to certainty of little or no impact at all, so the nuclear industry and “pro-nuclear environmentalists” conflate uncertainty of the mortality arising from Chernobyl and other nuclear disasters to certainty of few if any deaths. Their position is equally indefensible.

Before considering the misinformation of the nuclear industry and its advocates, I will briefly summarise the credible positions and scientific studies regarding the Chernobyl cancer death toll.

Epidemiological public health studies are, of course, important but they’re not much use in estimating the overall Chernobyl death toll. The effects of Chernobyl, however large or small, are largely lost in the statistical noise of widespread cancer incidence and mortality.

Estimates of collective radiation exposure are available ‒ for example, the International Atomic Energy Agency (IAEA) estimates a total collective dose of 600,000 Sieverts over 50 years from Chernobyl fallout. And the collective radiation dose can be used to estimate the death toll using the Linear No Threshold (LNT) model, which holds that the risks are proportional to dose. LNT enjoys heavy-hitting scientific support ‒ the 2006 report of the US National Academy of Sciences’ Committee on the Biological Effects of Ionising Radiation states that “the risk of cancer proceeds in a linear fashion at lower doses without a threshold”.

If we use the IAEA’s collective radiation dose estimate, and a risk estimate derived from LNT (0.1 cancer deaths per Sievert), we get an estimate of 60,000 Chernobyl cancer deaths. Sometimes a risk estimate of 0.05 is used to account for the possibility of decreased risks at low doses and/or low dose rates ‒ in other words, 0.05 is the risk estimate when applying a “dose and dose rate effectiveness factor” or DDREF of two. That gives an estimate of 30,000 deaths.

Any number of studies (including studies published in peer-reviewed scientific literature) use LNT ‒ or LNT with a DDREF ‒ to estimate the Chernobyl death toll. These studies produce estimates ranging from 9000 cancer deaths (in the most contaminated parts of the former Soviet Union) to 93,000 cancer deaths (across Europe).

Those are the credible estimates of the cancer death toll from Chernobyl. None of them are conclusive ‒ far from it ‒ but that’s the nature of the problem we’re dealing with.

Another defensible position is that the long-term Chernobyl cancer death toll is unknown and unknowable because of the uncertainties associated with the science.

The UN Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) states: “The Committee has decided not to use models to project absolute numbers of effects in populations exposed to low radiation doses from the Chernobyl accident, because of unacceptable uncertainties in the predictions. It should be stressed that the approach outlined in no way contradicts the application of the LNT model for the purposes of radiation protection, where a cautious approach is conventionally and consciously applied.”

So there are two defensible positions regarding the Chernobyl cancer death toll ‒ estimates based on collective dose estimates (with or without a DDREF or a margin of error in either direction), and UNSCEAR’s position that the death toll is uncertain.

A third position ‒ unqualified claims that the Chernobyl death toll was just 50 or so, comprising some emergency responders and a small percentage of those who later suffered from thyroid cancer ‒ should be rejected as spin from the nuclear industry and some of its supporters.

Those supporters include a small but vocal group of self-styled pro-nuclear environmentalists (PNEs). Climate scientist James Hansen and columnist George Monbiot cite UNSCEAR to justify a Chernobyl death toll of 43, without noting that the UNSCEAR report left open the question of long-term cancer deaths. Ecologist James Lovelock asserts that “in fact, only 42 people died” from the Chernobyl disaster.

Patrick Moore (founder of the Clean and Safe Energy Coalition), citing the UN Chernobyl Forum, states that Chernobyl resulted in 56 deaths. In fact, the Chernobyl Forum’s 2005 report estimated up to 4000 long-term cancer deaths among the higher-exposed Chernobyl populations, and a follow-up study by the World Health Organisation in 2006 estimated an additional 5000 deaths among people exposed to lower doses in Belarus, the Russian Federation and Ukraine.

Australian academic Barry Brook says the Chernobyl death toll is fewer than 60. Ben Heard, another Australian “ecomodernist”, claims that the death toll was 43.

In 2010, British author Mark Lynas said the Chernobyl death toll “has likely been only around 65”. Two years earlier, Lynas said that the WHO estimates “a few thousand deaths” (actually 9000 deaths) but downplays the death toll by saying it was “indiscernible” in the context of overall deaths. Yes, the Chernobyl death toll is indiscernible … and the 9/11 terrorist attacks accounted for an indiscernible 0.1 per cent of all deaths in the US in 2001.

There doesn’t appear to be a single example of a pro-nuclear environmentalist ‒ or a comparable organisation ‒ providing a credible account of the Chernobyl death toll. They’re perfectly entitled to follow UNSCEAR’s lead and argue that the long-term death toll is uncertain, but conflating or confusing that uncertainty with a long-term death toll of zero clearly isn’t a defensible approach.

The US Breakthrough Institute comes closest to a credible account of the Chernobyl death toll (which isn’t saying much), stating that “UN officials say that the death toll could be as high as 4000”.

However, the Breakthrough Institute ignores the follow-up World Health Organisation study that estimated an additional 5000 deaths in ex-Soviet states; scientific estimates of the death toll beyond ex-Soviet states; scientific literature regarding diseases other than cancer linked to radiation exposure; and indirect deaths associated with the permanent relocation of more than 350,000 people after the Chernobyl disaster.

Dr Jim Green is the national nuclear campaigner with Friends of the Earth Australia and editor of the Nuclear Monitor newsletter published by the World Information Service on Energy.