Radiation is safe within limits

Nuclear power is a green environmental solution. It generates no CO2. The fuel is cheap and inexhaustible. Advanced nuclear power can solve the global crises of air pollution deaths and climate change. Cheap energy can help developing nations escape poverty and let industrialized nations improve economic growth.

Is it safe? The primary obstacle to nuclear power is misunderstanding of radiation safety.

Most people have been incorrectly led to believe that:

  • There is no safe level of radiation.
  • Radiation effects are cumulative.
  • Chernobyl killed nearly a million people.
  • Nuclear waste is deadly for a million years.

These misunderstandings have created public fear, leading regulators to adopt unnecessary rules to isolate the public from even very tiny doses of radiation. The excess costs and delays have made nuclear power more expensive, impeding its benefits to people.

This video presentation from Environmental Progress founder, Michael Shellenberger gives key information on radiation safety:

Why I changed my mind about nuclear power | Michael Shellenberger | TEDxBerlin

Like fire, ionising radiation can be fatal if the dose is large enough. But like very briefly waving a lighted match under your finger, small doses of radiation are, in practice, harmless.

Our problem is we cannot feel the damaging effect of ionising radiation, and so imaginations run wild. Animals did not evolve to detect ionising radiation because in nature there is no need. Natural background radiation is completely harmless.

For example, people have been known to object to receiving a body scan at an airport owing to the radiation it emits, before boarding a plane where the dose they receive from increased exposure to cosmic rays far outweighs the minute dose from the airport scanner.

That is not entirely their fault. Authorities have not always shown themselves to be trustworthy, and little public education exists on ionising radiation.

Next: Game Changers

The rest of this page contains technical information about radiation: radioactive materials, safe dose rates, evidence and radiation politics.


Radioactive materials have atoms that decay at random. Half of them decay within their half-life. Some examples are:

potassium-401.2 billion years
americium-241432 years
cobalt-605 years
iodine-1318 days

Radiation results from each atom’s decay.

  • Alpha particles (two protons + two neutrons) cannot penetrate skin.
  • Beta particles (electrons ejected from nuclei) do not penetrate metal foil.
  • Gamma radiation (energetic photons) is partly absorbed by bone to make X-ray images.

Radioactivity of a source is measured by counting atomic decays. One count per second is one Becquerel (Bq). A banana has beta radioactivity of about 15 Bq from its potassium-40. Smoke detectors have americium-241 – made in nuclear reactors – with alpha radioactivity of about 30,000 Bq.

Ionising radiation dose is the energy transferred from radiation to body tissue. A one milliSievert (mSv) dose is 0.001 watt-second of energy per kilogram of tissue (x20 for alpha particles). One mammogram1 exposure, for example, may be 2 mSv. Natural background radiation comes from cosmic rays, from breathing radon, from ingestion of food and water, and from proximity to rocks such as granite. Natural radiation dose rates vary, averaging 3 mSv/year in the US, 4 mSv/y in Denver, and 7 mSv/y in Finland.

(Other units are also in common use. For details see, for instance, http://orise.orau.gov/reacts/guide/measure.htm )


A massive, single, whole-body radiation dose severely injures blood cell production and the digestive and nervous systems. A dose over 5,000 mSv is usually fatal. Spread over a lifetime it is harmless. Why? At low dose rates cells have time to recover. Cancer is not observed2 at dose rates below 100 mSv/y.

Linear response

Radiation can break a chemical bond in a DNA molecule and create a slight chance it might recombine improperly to propagate cancerous cells. Linear no threshold theory (LNT) says the chance is proportionate just to radiation dose, even at low dose rates over long times. It’s wrong.

Hermann Muller received the Nobel prize in 1946 for LNT theory. He used fruit flies exposed3 to 2,750 mSv and up. But to heighten public fear of atomic bomb fallout during the Cold War, he extrapolated his results down to below 100 mSv, despite contrary evidence.

The flaw in old LNT theory is that it considered only radiation dose, not dose rate. LNT theory ignored life’s adaptive response.

Adaptive response

Radiation can be safe. We now know that DNA strands break and repair frequently, about 10,000 times per day per cell. MIT researchers observed4 that 100 mSv/y radiation dose rates increased this number. The overwhelming majority of breaks are caused by ionized oxygen molecules from metabolism within the cell. Because DNA is a double helix, the duplicate information in one strand lets enzymes readily repair any single-strand break.

Double strand breaks also occur naturally, about once per week per cell. Most such breaks are due to intracellular oxygen, with natural background radiation increasing the break rate5 by about 0.1%. Specialized repair centers within cells fix these breaks, as observed by scientists at Lawrence Berkeley Labs5.

Adaptive response continues at the cellular, tissue, and organism levels. This protection5 peaks near 100 mSv exposure and persists for a year or so. The process is similar to immune response to vaccinations against smallpox, polio, or influenza.


The examples given below show that radiation is safe below 100 mSv/y and that LNT is wrong.

Atomic bomb survivors

The US exploded atomic bombs over Japan in 1945, killing 200,000 people. 93,000 survivors have since been closely monitored for health effects. In 55 years 10,423 survivors died from cancer, 573 more than the 9,850 deaths normally expected by comparison with residents away when the bombs exploded. But there were no cancer deaths8 observed from radiation doses less than 100 mSv.

Taiwan apartment buildings

Recycled steel contaminated with cobalt-60 was used to build apartments, exposing 8,000 people to 400 mSv of radiation over 20 years. Cancer incidence was sharply down, not up 30% as LNT predicted. Instead the adaptive response to low-level radiation seemed to confer health benefits.


Doses up to 8,000 mSv killed 28 emergency workers at Chenobyl in 1986. The Chernobyl Forum10 estimated up to 8,000 children contracted thyroid cancer from milk contaminated with iodine-131, and 15 died. Relying on LNT theory, the report projected up to 4,000 future fatal cancers might occur, but these have not been observed among the 100,000 fatal cancers normally expected.

US nuclear shipyard workers

The US studied workers maintaining nuclear submarines who were exposed to low levels of gamma radiation from cobalt-60. The study compared 28,000 nuclear workers and 33,500 non-nuclear workers. People exposed to more radiation (averaging 8 mSv/y) had a death rate11 from all causes 24% less than the others. This contradicts LNT theory.

Medical radiation

Radiation medicine exposes a US person to 3 mSv/y on average. Diagnostic radiation doses12 are low, ranging from 0.001 mSv for a dental X-ray to 20 mSv for a CT procedure.

Therapeutic doses13 are high. A rotating X-ray beam focused on cancer tissue delivers up to 80,000 mSv. To minimize the risk of causing cancer in nearby tissue, radiologists divide the radiation dose into fractions, administered daily rather than all at once, giving healthy tissue time to recover. If LNT were true this fractionated radiation therapy wouldn’t work


The tsunami-flooded reactors overheated and released radioactive materials. Residents were evacuated from areas with greater than 20mSv/y exposure (IAEA14 recommends this at greater than 220 mSv/y). A UN panel of expert scientists concluded15 that radiation caused no attributable health effects and none likely in the future. Radiation released killed no one, but evacuation stress was reported to have killed hundreds. Most refugees could have returned home safely.


Exposure limits that were set by LNT theory ignore observed low-level radiation effects. Public radiation safety limits have become more restrictive, from 150 mSv/y (1948) to 5 mSv/y (1957) to 1 mSv/y (1991).

These rules are political and inconsistent. Nuclear workers are allowed 50 mSv/y, and astronauts 500 mSv/y. EPA’s limit for indoor radon is 8 mSv/y, but 0.04 mSv/y for tritium in drinking water. EPA limits Yucca Mountain exposure to < 0.1 mSv/y for 10,000 years.

The LNT fallacy that any radiation can kill you led to the ALARA principle (as low as reasonably achievable). But achievability is based on ever-changing technology capability, not on health effects. LNT and ALARA ratchet limits lower and increase costs and fear.

Next: Game Changers > Human Strengths

Notes and references 

1.   “mammogram exposure”
Radiation Doses and Cancer Risks from Breast Imaging Studies
by R. Edward Hendrick, PhD

2.    “cancer is not observed at dose rates below 100 mSv/y”
The Linear No-Threshold Relationship Is Inconsistent with Radiation Biologic and Experimental Data
by Maurice Tubiana, MD, Ludwig E. Feinendegen, MD, Chichuan Yang, MD, and Joseph M. Kaminski, MD

3.    “fruit flies exposed”
How the US National Academy of Sciences misled the world community on cancer risk assessment: new finding challenge historical foundations of the linear dose response

by Edward J. Calabrese


See also http://www.ncbi.nlm.nih.gov/pubmed/22166484

4.    “MIT researchers observed”

A new look at prolonged radiation exposure
by Anne Trafton, MIT News

Integrated Molecular Analysis Indicates Undetectable Change in DNA 

Damage in Mice after Continuous Irradiation at ~ 400-fold Natural 

Background Radiation
by Werner Olipitz et al


5.    “break rate”
Hormesis by Low Dose Radiation Effects: Low-Dose Cancer Risk Modeling Must Recognize Up-Regulation of Protection

by Ludwig E. Feinendegen, Myron Pollycove, and Ronald D. Neumann

6.    “observed by scientists at Berkeley Labs”

Evidence for formation of DNA repair centersand dose-response nonlinearity in human cells
by Teresa Neumaiera et al

7.   “10,423 died”

Radiation and Reason, p 89, Table 4, p 91 Table 5
by Wade Allison




Table 4 (leukemia)
 Dose range
 Survivors Observed deaths Expected deaths
   <5 37,407 92 85
    5 to 100 30,387 69 72
 100 to 200 5,841 14 15
 200 to 500 6,380 27 16
 500 to 1000 3,963 20 10
 1000 to 2000 1,972 39 5
 > 2000 737 25 2
 ____________ ___________ ___________ __________
 All 86,955 296 203
Table 5 (solid cancer)
 Dose range
 Survivors Observed deaths Expected deaths
   <5 38,507 4,270 4,282
    5 to 100 29,960 3,387 3,313
 100 to 200 5,949 732 691
 200 to 500 6,380 815 736
 500 to 1000 3,426 483 378
 1000 to 2000 1,764 326 191
 > 2000 625 114 56
 ____________ ___________ ___________ __________
 All 86,611 10,127 9,647

8.    “no cancer deaths”
Radiation and Reason pp 89, 91, Tables 4 and 5, first two rows

9.    “cancer incidence was sharply down”

Effects of Cobalt-60 Exposure on Health of Taiwan Residents Suggest New Approach Needed in Radiation Protection

by W.L. Chen et al


Hemopoietic Response to Low Dose-Rates of Ionizing Radiation Shows Stem Cell Tolerance and Adaptation

by Theodor M. Fliedner et al


10.    “contaminated with iodine-131, and 15 died”
Chernobyl’s Legacy: Health, Environmental and Socio-Economic Impacts
by Chernobyl Forum

11.    “death rate from all causes”

Nuclear shipyard worker study (1980–1988): a large cohort exposed to low-dose-rate gamma radiation 

by Ruth Sponsler and John R. Cameron


12.    “Diagnostic radiation doses are low”

Radiation Dose in X-Ray and CT Exams

by American College of Radiology and Radiological Society of North America


13.    “Therapeutic doses are high”

Radiation therapy

by Wikipedia


14.    “IAEA recommends > 220 mSv/y”

Actions to Protect the Public in an Emergency due to Severe Conditions at a Light Water Reactor

by UN International Atomic Energy Agency


15.    “UN panel of expert scientists”

No Immediate Health Risks from Fukushima Nuclear Accident Says UN Expert Science Panel

by United Nations Scientific Committee on the Effect of Atomic Radiation


16.    “Evacuation stress”

Commentary on the Appropriate Radiation Level for Evacuations

by Jerry Cuttler


Fukushima evacuation zone November 2013 radiation, p 3
by Japan Nuclear Regulation Authority
Evacuation boundary line radiation 20 mSv/y, outside orange area <100 mSv/y

This information is also available as http://home.comcast.net/~robert.hargraves/public_html/RadiationSafety26SixPage.pdf

from: Robert Hargraves <robert.hargraves@gmail.com> author of  THORIUM: energy cheaper than coal