The Fallout Hypothesis 2

A few months back, in The Fallout Hypothesis, I explored the idea that many cancers, including lung cancer, were caused by radioactive fallout from atmospheric nuclear weapons tests between 1945 and 1963. Fredrik Eich became interested in the idea, with the slight variation that fallout would tend to be maximized in places where there was high rainfall. He started his own investigation, and his own blog. Last week he put up a post with a rainfall map of the USA next to a cancer mortality map of the USA. There’s quite a good fit.

There doesn’t seem to have been very much knowledge of the dangers of radiation at the time the nuclear bomb tests began. From Biology and the Bomb:

On March 31, 1954, nearly a month after Bravo, the chairman of the AEC, Admiral Lewis Strauss, stated that nuclear tests had resulted in a small increase in radiation in some places in the United States. He claimed that this increase was “far below the levels which could be harmful in any way to human beings.”

Strauss assumed that, as in the case of many chemical toxins, there existed a threshold dose below which radiation did no harm and that the low dose to which the public was exposed did not exceed this threshold. The threshold assumption was widely held—in fact, shoe stores of the day routinely contained X-ray boxes so that patrons could see the bones in their feet.

Only a select community of biologists understood that the United States and Soviet governments were killing people without realizing it. In the late 1920s, geneticist Hermann Muller had discovered that high-energy radiation caused genetic mutations in fruit flies at a rate proportional to the dosage received. (He won the Nobel Prize for this in 1946.) After the H-bomb tests became public knowledge, he felt morally obligated to warn policymakers and the public about the risk of mutations in the germ line—the reproductive cells in the testes and ovaries—from radioactive fallout.

Also this Wikipedia graph of Carbon-14 (radiocarbon) concentration in the atmosphere:

atmospheric C-14, New Zealand[red] and Austria[green]. The New Zealand curve is representative for the Southern Hemisphere, the Austrian curve is representative for the Northern Hemisphere. Atmospheric nuclear weapon tests almost doubled the concentration of Carbon-14 in the Northern Hemisphere. The Delay of some years after the Partial Test Ban Treaty (PTBT) of the peak on the Southern Hemisphere can be explained by the time for the propagation of C-14 from the Northern Hemisphere to the Southern Hemisphere.

This shows that nuclear tests doubled the amount of C-14 in the atmosphere. Cesium-137 has a half life of 30 years, but C-14 has a half life of 5,600 years. The decay curve in the graph above is not a radioactive decay curve. Pretty much none of the C-14 has decayed away. It’s still around. What the graph shows how rapidly C-14 fell out of the atmosphere onto the surface of the planet.

Back in the 1950s, most concern was about possible human mutations, and with the more energetic fast-decaying radioactive fallout such as Cesium 137 and Strontium 90. Carbon-14 was largely dismissed as a health risk, probably because it decays so slowly. But I found a draft of a paper by multi-Nobel-prize-winning chemist Linus Pauling about C-14, written in the late 1950s, which began:

In his discussion of bomb-test carbon-14 he [Willard Libby] said that "Fortunately, this radioactivity is essentially safe because of its long lifetime and the enormous amount of diluting carbon dioxide in the atmosphere." He pointed out that 5.2 tons of neutrons would be needed to "double the feeble natural radioactivity of living matter due to radiocarbon. Such an increase would have no significance from the standpoint of health."

Pauling had initially been reassured by Libby, but a couple of years later performed his own calculations, and drew a different conclusion:

It is concluded that one year of testing (30 megatons of fission plus fusion) is predicted to cause in the world (estimated future number of births 3 times the present) an estimated total of about 223,OOO seriously defective children to be born (stillbirth, childhood death, gross physical or mental defect) plus about 423,000 embryonic and neonatal deaths. These numbers are about 20 times the numbers usually estimated as the probable effects of the fallout fission products from one year of testing. In addition, the somatic effects of bomb-test carbon-14 are predicted to be about equal to those of fission products, including strontium-90, with respect to causing leukemia and bone cancer, and much greater than those of fission products with respect to diseases resulting from radiation damage to tissues other than bone tissue and bone marrow.

This paper has "First draft" written in the top right hand corner, and it has several corrections – including the "much" that has been crossed out by hand in the passage above.

A much more recent (2005) article in American Scientist considers the cancer risks of fallout.

By the early 1960s, there was no place on Earth where the signature of atmospheric nuclear testing could not be found in soil, water and even polar ice. Cancer investigators who specialize in radiation effects have, over the intervening decades, looked for another signature of nuclear testing—an increase in cancer rates…

The earliest concern about health effects from exposure to fallout focused on possible genetic alterations among offspring of the exposed. However, heritable effects of radiation exposure have not been observed from decades of follow-up studies of populations exposed either to medical x rays or to the direct gamma radiation received by survivors of the Hiroshima and Nagasaki bombs. Rather, such studies have demonstrated radiation-related risks of leukemia and thyroid cancer within a decade after exposure, followed by increased risks of other solid tumors in later years. Studies of populations exposed to radioactive fallout also point to increased cancer risk as the primary late health effect of exposure. As studies of biological samples (including bone, thyroid glands and other tissues) have been undertaken, it has become increasingly clear that specific radionuclides in fallout are implicated in fallout-related cancers and other late effects…

It discusses the distribution of fallout.

Large particles settle locally, whereas small particles and gases may travel around the world. Rainfall can cause localized concentrations far from the test site. On the other hand, large atmospheric explosions injected radioactive material into the stratosphere, 10 kilometers or more above the ground, where it could remain for years and subsequently be deposited fairly homogeneously ("global" fallout)…

Following the deposition of fallout on the ground, local human populations are exposed to external and internal irradiation. External irradiation exposure is mainly from penetrating gamma rays emitted by particles on the ground. Shielding by buildings reduces exposure, and thus doses to people are influenced by how much time one spends outdoors.

Internal irradiation exposures can arise from inhaling fallout and absorbing it through intact or injured skin, but the main exposure route is from consumption of contaminated food. Vegetation can be contaminated when fallout is directly deposited on external surfaces of plants and when it is absorbed through the roots of plants.

As well as being produced by weapons tests, Carbon-14 is produced naturally in the upper atmosphere, so that about one in one trillion carbon atoms is Carbon-14 rather than regular non-radioactive Carbon-12. These radiocarbon atoms are incorporated into plants and animals, and humans as well. It can be used to date when people were born, according to Nature.

we show that the amount of radiocarbon present in tooth enamel as a result of nuclear bomb testing during 1955–63 is a remarkably accurate indicator of when a person was born. Age is determined to within 1.6 years, whereas the commonly used morphological evaluation of skeletal remains and tooth wear is sensitive to within 5–10 years in adults

And in a 2005 Scientific American, Cold War Clues:

Frisen learned of a natural tag unique to people born after 1955, when aboveground testing of nuclear weapons increased substantially. The explosions, which stopped after the 1963 Limited Test Ban Treaty, threw enormous amounts of carbon 14 isotope into the atmosphere that quickly diffused around the globe. Plants incorporated the carbon 14 into their cells, animals ate the plants, and people ate both, absorbing the isotope into their own cells

There are several interesting things here. It seems that my idea in my previous essay that people are more in danger of fallout if they’re outside buildings is true. I’d suggested that this might be the reason why women (or rather housewives) got less lung cancer than men, on the grounds that they spent more time time indoors than men who would be going out to work every day, and would sometimes be working outside.

It also seems that Fredrik Eich’s suggestion that rainfall concentrates fallout in high rainfall areas is also true. It would be interesting to see whether the amount of rainfall in a country correlates with the incidence of cancer. On the other hand, exposure outdoors is likely to be affected by how much clothing is worn, which would suggest that in cold northern countries, where people may spend months wearing hats and scarves and gloves and overcoats, they are less exposed to the external environment than, say, Mediterranean countries where people will be wearing far less. Also people in relatively poor countries may be supposed to get more exposure, because they walk or cycle, while people in rich countries who do most of their travelling in cars or trains.

A further interesting observation is that if one in a trillion carbon atoms is Carbon-14, and there are about 7.0 x 10^26 carbon atoms in the human body, then I have 7.0 x 10^14 or 700,000,000,000,000 or about a billion trillion Carbon-14 atoms in my body gradually decaying. It would be interesting to know whether they are evenly distributed, or tend to concentrate in particular organs or tissues.

Another point is that throughout much of the 1940s and 1950s, there was little understanding of the dangers of fallout, except among a few biologists. But by 1950, the cause of lung cancer had been declared to be smoking cigarettes. The US Surgeon General’s 1964 report made this the official medical view – just a year after the Test Ban Treaty that stopped atmospheric weapons tests.

And although we hear a lot about the chemical carcinogens in tobacco smoke (e.g. benzapyrene), they never mention Carbon-14 or other radioactive fallout. The only one they do mention is Polonium-210, which has a half life of 138 days, and so will be pretty harmless after a couple of years.

Smokers may have been at more risk from lung cancer, not because they were smoking tobacco, but because they were inhaling more radioactive carbon compounds into their lungs than non-smokers. This would have been true if they’d been smoking marijuana or opium or wood smoke rather than tobacco.

If radioactive fallout is the real cause of most cancers, more or less everybody would have got a dose of fallout in the 1950s and 60s and 70s, some of which they’re still carrying around with them to this day.