Radiation and Cancer: Risks of Leukemia in Nuclear Workers More Than Double Previous Estimate
By Ian Fairlie | CounterPunch | October 16, 2015
In 2013, I discussed several epidemiological studies providing good evidence of radiogenic risks at very low exposure levels.
A powerful new study has been published in Lancet Haematology [1] which adds to this evidence. However the study’s findings are more important than the previous studies, for several reasons.
First, it provides “strong evidence”, as stated by the authors, of a “dose-response relationship between cumulative, external, chronic, low-dose, exposures to radiation and leukaemia”.
Second, it finds radiogenic risks of leukemia among nuclear workers to be more than double the risk found in a previous similar study in 2005. The excess relative risk of leukaemia mortality (excluding workers exposed to neutrons) was 4.19 per Gy.
In 2005, a similar study [2] among nuclear workers (also excluding those exposed to neutrons) in 15 countries by several of the same authors found an ERR of 1·93 per Sv. In other words, the new study’s risk estimates are 117% higher than the older study. The clincher is that the new study’s estimated risks are much more precise than before.
Third, it confirms risks even at very low doses (mean = 1·1 mGy per year). Unlike the Japanese bomb survivors’ study, it observes risks at low dose rates rather than extrapolating them from high levels.
Fourth, it finds risks do not depend on dose rate thus contradicting the ICRP’s use of a Dose Rate Effectiveness Factor (DREF) which acts to reduce (by half) the ICRP’s published radiation risks.
Fifth, it finds radiogenic leukemia risks decline linearly with dose, contradicting earlier studies suggesting a lower, linear-quadratic relationship for leukemia. It strengthens the Linear No Threshold (LNT) model of radiogenic risks, as it now applies to leukemias as well as solid cancers.
Sixth, the study finds no evidence of a threshold below which no effects are seen (apart from zero dose).
Seventh, the study uses 90% confidence intervals and one-sided p-values. In the past, 95% intervals and two-sided p-values were often incorrectly used which had made it harder to establish statistical significance.
Explanation for change
In an earlier version of this blog posted on 29th June 2015, I’d written that the increase between the 2005 study and the present study was 50%, ie up from 1.93 to 2.96 per Gy. This was because the study’s ‘Discussion’ section specifically compared these two studies and their risks, stating the older study’s leukemia risk was smaller and less precise.
However a detailed examination of the report reveals the following sentence in the para immediately before the Discussion section:
“We assessed the effect of excluding people who had recorded neutron exposures; we showed a positive association for leukaemia … (ERR per Gy 4·19, 90% CI 1·42-7·80, 453 deaths)…”.
To make sure readers get the point, the risk is greater when neutron exposed workers are excluded. This is important because the 2005 study excluded workers exposed to neutrons. Therefore the correct comparison is between the risks for non-neutron workers, that is between 4.19 and 1.93 per Gy – an increase of 117%, rather than 50%.
I’ve written to the report’s authors about this but have not received any replies yet. I shall keep readers up-to-date on any progress.
Study’s credentials
The study’s credentials are pretty impeccable. It’s a huge study of over 300,000 nuclear workers adding up to over 8 million person years, thus ensuring its findings are statistically significant, ie with very low probability of occurring by chance.
Also, it’s an international study by 13 respected scientists from national health institutes in the US, UK, and France, as follows.
*Centers for Disease Control and Prevention, US
*National Institute for Occupational Safety and Health, US
*Department of Health and Human Services, US
*University of North Carolina, US
*Drexel University School of Public Health, US
*Public Health England, UK
*Institut de Radioprotection et de Sûreté Nucléaire, France
*Center for Research in Environmental Epidemiology, Spain
*UN International Agency for Research on Cancer, France
Funding was provided by many institutions, including US Centers for Disease Control and Prevention, US National Institute for Occupational Safety and Health, US Department of Energy, US Department of Health and Human Services, Japanese Ministry of Health Labour and Welfare, French Institut de Radioprotection et de Sûreté Nucléaire, and the UK’s Public Health England.
My conclusions
This study powerfully contradicts the views of ill-informed and inexperienced journalists (including the UK writer George Monbiot) [3] and self-styled scientists who argue that radiation risks are over-estimated and even that radiation is somehow good for you.
Hormetic effects are neither found nor discussed in this study: such irrelevant effects are regarded by real scientists as beneath their consideration.
The impressive list of contributing scientists and their national institutions here should serve to make radiation risk deniers reconsider their views. This is particularly the case for US risk deniers, in view of the many US agencies and US scientists backing the study.
The study pointedly comments that:
“At present, radiation protection systems are based on a model derived from acute exposures, and assumes that the risk of leukaemia per unit dose progressively diminishes at lower doses and dose rates.”
The study shows this assumption is incorrect. The authors therefore join with WHO and UNSCEAR scientists in their views that DREFs should not be used. The question remains whether the ICRP will accept this powerful evidence and scrap their adherence to using DREFs. I advise readers not to hold their breaths.
As regards the implications of their study, the authors interestingly choose to comment – not on exposures from the nuclear industry – but from medical exposures. They state:
“Occupational and environmental sources of radiation exposure are important; however, the largest contributor to this trend is medical radiation exposure. In 1982, the average yearly dose of ionising radiation from medical exposures was about 0·5 mGy per person in the USA; by 2006, it had increased to 3·0 mGy.
“A similar pattern exists in other high-income countries: use of diagnostic procedures involving radiation in the UK more than doubled over that period and more than tripled in Australia. Because ionising radiation is a carcinogen, its use in medical practice must be balanced against the risks associated with patient exposure.
This is all correct and worrying, especially the revelation that medical radiation doses increased 6-fold in the US and doubled in the UK between 1982 and 2006. The authors add:
“This finding shows the importance of adherence to the basic principles of radiation protection – to optimise protection to reduce exposures as much as reasonably achievable and – in the case of patient exposure – to justify that the exposure does more good than harm.”
The same, of course, applies to exposures from the nuclear industry – the actual subject of their research.
Dr Ian Fairlie is an independent consultant on radioactivity in the environment. He has a degree in radiation biology from Bart’s Hospital in London and his doctoral studies at Imperial College in London and Princeton University in the US concerned the radiological hazards of nuclear fuel reprocessing. Ian was formerly a DEFRA civil servant on radiation risks from nuclear power stations. From 2000 to 2004, he was head of the Secretariat to the UK Government’s CERRIE Committee on internal radiation risks. Since retiring from Government service, he has acted as consultant to the European Parliament, local and regional governments, environmental NGOs, and private individuals.
Iranian researchers produce anti-cancer nano-drug
Press TV – April 27, 2015
Iranian researchers have produced a nano-drug which has proven effective in battling treatment resistant cancers.
The Cancer Research Center of Tehran University of Medical Sciences produced the polymer-based nanocarrier for the targeted release of the anti-cancer drug curcumin, ISNA reported on Sunday.
“This nanocarrier was made without the use of poisonous catalysts and has proven successful in clinical trials on a number cancer patients,” said Dr Ali Mohammad Alizadeh from the Iran Nanotechnology Initiative Council.
Research has proven that curcumin, which is found in turmeric, has anti-cancer and cancer preventing properties apart from its anti-oxidant and anti-inflammatory properties, he added.
When curcumin is prescribed in its edible form, it has a low effect on the targeted tissues because of its low absorption rate and fast metabolism which causes it to be flushed from the body, he noted.
However, by capsuling curcumin in nano-emulsions (nano curcumin) its medical properties increase, Alizadeh noted.
Even if prescribed in high dosages, the drug is proven not poisonous during first-stage clinical trials and is currently near the end of stage two clinical trials on drug-resistant breast and digestive tract cancers.
Alizadeh added that because all the basic materials required to manufacture nano-curcumin are available in the country it can be domestically mass-produced as an anti-cancer drug.
Just in case you missed it, here’s why radiation is a health hazard
By Tilman Ruff | The Conversation | March 25, 2011
The March 11 earthquake and tsunami in Japan and complicating nuclear crisis throw into sharp focus concerns about exposure to ionising radiation. What is it, how is it harmful, how much is too much? Inside a nuclear reactor, the radioactivity is increased about a million times as some of the uranium or plutonium is converted to a cocktail of hundreds of different radioactive elements.
There are many different pathways through which people can be exposed to radiation: inhalation of gases or particles in the air, deposits in soil or water, ingestion of food, water or dust. Some radioisotopes mimic normal chemical elements in living systems and therefore make their way up the food chain and onto our plates.
Ionising radiation
Radiation is called “ionising” when it has sufficient energy to knock the electrons off atoms to produce ions (atoms which have a net positive or negative electrical charge).
Ionising radiation damages large complex molecules either directly or by creating highly reactive chemicals inside cells.
The biological potency of ionising radiation is not related to the amount of energy it contains so much as that this energy is packaged in a form which can reach and damage complex molecules – particularly the DNA that is our genetic blueprint, that is passed on to form each new generation.
A lethal dose of radiation may contain as little energy as the heat in a cup of coffee. Our senses cannot warn us about ionising radiation – it cannot be seen or touched or felt or tasted or smelt.
Levels of exposure
Some effects of radiation only occur above certain thresholds.
In the short term, high levels of radiation exposure can cause acute radiation sickness. In the longer term there is an increased risk of cataracts, birth defects, sterility and hair loss.
High doses of radiation can kill cells – this is the reason targeted radiation is used in the treatment of some cancers.
Acute radiation exposure at doses over 100 milliSieverts (mSv), and particularly over 1000 mSv, has most impact on our rapidly dividing cells. These are the blood-forming cells of the bone marrow, lining of the gut, and ovaries and testis. The symptoms of acute radiation sickness therefore include vomiting and diarrhea, bleeding, and reduced ability to fight infection.
The major long-term effect of ionising radiation exposure is an increased risk of a wide variety of cancers. There is no “safe” level of radiation below which there is no increase in cancer risk. The earliest to appear, after around three to five years, are leukemia and thyroid cancer. The 1986 Chernobyl disaster, for instance, has resulted in an epidemic of thyroid cancer with 6,500 children affected so far.
Other cancers begin increasing after 10 years – lung, breast, colon, ovary, bladder and many others. Excess rates of cancer in the Hiroshima and Nagasaki survivors continue to rise.
Sources of exposure
All of us are exposed to ionising radiation all the time – from the stars, from the earth and rocks, from common equipment and appliances. The global average estimated human exposure is 2.4 mSv per year.
The biggest natural source is radon gas produced from radium, part of the decay chain of uranium, which is widely distributed in the Earth’s crust. After smoking, radon is the second most important cause of lung cancer worldwide.
The bulk of ongoing exposures of human origin are from medical X-rays, and there is considerable concern about the rapidly rising medical radiation exposures, particularly from the growing number of CT scans being performed. CT scans involve radiation doses of between 3 and 11 mSv.
Exposure to ionising radiation from all sources should be kept as low as is feasible.
In Australia and most countries, it is recommended that 1 mSv per person per year be the maximum permissible exposure from non-medical sources for the general population; and 20 mSv per year the annual permissible limit for nuclear industry workers. In Japan the maximum permissible dose for the emergency nuclear workers in Fukushima has been increased to 250 mSv.
Health harms
The most authoritative current estimates of the health effects of low dose ionising radiation are contained in the Biological Effects of Ionising Radiation VII report from the US National Academy of Sciences (BEIR VII).
This report reflects the substantial weight of scientific evidence that there is no exposure to ionising radiation that is risk-free. The greater the exposure, the greater the risk.
BEIR VII estimates that each 1 mSv of radiation is associated with an increased risk of solid cancer (cancers other than leukemia) of about 1 in 10,000; an increased risk of leukemia of about 1 in 100,000; and a 1 in 17,500 increased risk of cancer death.
But while radiation protection standards are typically based on adult males, it is important to note that not everyone faces the same level of risk. For infants (under 1 year of age) the radiation-related cancer risk is 3 to 4 times higher than for adults; and female infants are twice as susceptible as male infants.
Females face a lower risk of leukemia, but a 50% greater risk of developing a more common solid tumour, so their overall risk of cancer related to radiation exposure is 40% greater than for males. Fetuses in the womb are the most radiation-sensitive of all.
Over time, estimates of the health risks associated with radiation exposure have inexorably risen.
Some of these risks are probably still under-estimated, particularly the impact of internal contamination, such as from plutonium particles lodging in the lung. Internal contamination may not be picked up by external devices designed to detect gamma radiation alone, such as the hand-held radiation monitors now being widely used to screen people in Japan.
In Germany, a recent national study showed that normal operation of nuclear power plants in Germany is associated with a more than doubling of the leukemia risk for under five year olds living within 5 km of a nuclear plant, and increased risk was seen to more than 50 km away. This was much higher than expected.
The longevity of some radioactive minerals is almost incomprehensible. Plutonium-239 has a half-life of 24,400 years. It will take almost a quarter of a million years for it to decay to less than one thousandth of the starting level. So the same particle inhaled into someone’s lung could go on to increase cancer risk for other individuals over successive generations.
Dr. Ruff is Associate Professor, Disease Prevention & Health Promotion Unit, Nossal Institute for Global Health at the University of Melbourne. He is IPPNW’s regional vice president for Southeast Asia and the Pacific, and is Chair of the International Campaign to Abolish Nuclear Weapons (ICAN).
Related articles
- Fukushima whitewash betrayed trust of NPR listeners (alethonews.wordpress.com)
- Japanese adults and children in Fukushima told to endure radiation on par with nuclear plant workers (civisjournal.wordpress.com)
- Media, Academia Join Forces to Downplay Dangers of Nuclear Power (alethonews.wordpress.com)
- Are medical imaging procedures always worth the risk? (news.cnet.com)