Radiation Life

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ENERGY 9/23/2015 @ 6:31AM 12,663 views

Is Radiation Necessary For Life?It seems so. Recent studies on the biological effects ofradiation carried out under radiation levels fromnatural background to essentially zero radiation,demonstrate that the absence of radiation is not goodfor organisms (Castillo et al., 2015).

Following experiments with microbes and humanlung cells that showed similar results, these newexperiments, led by researchers at New Mexico StateUniversity, with different bacterial species show thatgrowth was inhibited by the lack of radiation,contradicting the predictions of traditional hypothesesconcerning the biological effects of radiation.

There has been an 80-year discussion about the healtheffects of radiation on humans and other biologicalorganisms. High levels, or doses, obviously haveadverse effects, and really high doses can kill.

But low doses, those less than 10 rem (0.1 Sv) peryear, have been extremely difficult to evaluatebecause their effects are so minor that it’s impossibleto see any effects in a general population where otherevery-day adverse health effects overwhelm anythingfrom the radiation. Also, at low doses, all organismshave cellular repair and response mechanisms that cankeep adverse health effects from occurring, somethingthat evolved as life evolved (PNAS 2011).

James Conca Contributor

I write about nuclear, energy and the environment

Opinions expressed by Forbes Contributors are their own.

Is Radiation Necessary For Life? - Forbes http://www.forbes.com/sites/jamesconca/2015/09/...

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Biological Effects of Radiation are well known at high doses (data points shown)from the Japanese Bomb Survivors, the Chernobyl workers, and a few individualaccidents involving high levels of radiation. At low doses, however, there is littleeffect, which disappears in the noise of everyday adverse health effects. In the1950s we decided to just draw a straight line from the high dose effects to zero,calling it the Linear No-Threshold (LNT) dose hypothesis (red line), and assumedfor convenience and conservatism that there was no threshold below which noadverse health effects occurred. But there appears to be a threshold at the highend of natural background across the Earth, at about 10 rem (0.1 Sv), belowwhich no obvious effects can be seen (blue line). The results of this study indicateLNT is not correct at low doses and the blue line more closely predicts biologicaleffects of radiation than the simplistic red line. Source: Dr. Geof Smith, NMSU,and Dr. Ray Guilmette, Emeritus, LRRI

In the 1950s, it was decided, in the absence of data atlow doses, that low doses were bad, and that there wasno threshold below which radiation did not result inadverse health effects. This hypothesis, called theLinear No-Threshold (LNT) dose hypothesis, wasadopted throughout the world as the mostconservative regulatory response to the rising use ofradiation, the threat of atomic weapons, and thenewly-emerging nuclear industry.

LNT states that any amount of radiation increases therisk of organisms to accumulate negative healtheffects. According to LNT, no radiation would be thebest state for any organism, and the world adopted theAs Low As Reasonably Achievable (ALARA)approach to all issues involving radiation (see figureabove).

This is not just an academic issue. In practice,ALARA became As Low As TechnologicallyAchievable, and brought about extreme costs andunanticipated side-effects that have cost the worldalmost a trillion dollars over the last 60 yearsprotecting against low levels of radiation with nodemonstrable benefits.


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But the unwarranted fear of low doses of radiation haskilled thousands, and destroyed millions of livesfollowing WWII, the Chernobyl disaster and theFukushima accident through over-reaction,unnecessary forced evacuations, and the creation oflarge refugee communities (Japan Times).

Recent studies show that even nuclear disasters do notincrease radiation levels in surrounding areas muchabove these low background levels at most distancesaway from the source (WNN, NYTimes), as we’veseen at Fukushima and Chernobyl.

Many studies since 1950 have attempted to study theeffects of low levels of radiation on organisms,especially humans. But the results have been difficultto interpret because it has been difficult to separateradiation effects from non-radiation effects.

Therefore, if LNT is correct and no radiation is thebest state for any organism, the obvious experimentwould be to grow organisms in an environment thathas almost no radiation and observe how they respondcompared to the same organisms grown inbackground or higher levels of radiation (1, 2, 3).

A group of scientists designed and carried out a studyto do just that – approach the problem from the otherside of background, from as low a radiationenvironment as is possible to achieve on Earth(Castillo et al., 2015; Smith et al., 2011).


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The LBRE Experimental set-up, 2150 ft below the Earth’s surface in the massivesalts of the WIPP nuclear repository in New Mexico. Inset is the pre-WWII steelchamber (left) and the room hollowed out of the salt in the north end of theunderground facility far away from any waste that holds the experimentalchamber. Radiation levels here are 400 times below Earth surface background,ironic given that this is a nuclear waste repository. Source: DOE

(Full Disclosure – I was one of the three scientistsfrom NMSU and DOE that began this study in 2007,designing the tests, providing the laboratory space,resources and funding, and setting-up the originalexperiments, almost a half-mile below ground inCarlsbad, New Mexico).

Since we can’t experiment on people, and it’s difficultto control random human populations with respect toradiation levels, this study focused on measuring themolecular evidence of a biological stress response intwo species of bacteria, under different levels ofradiation.

One species is very sensitive to radiation, Shewanellaoneidensis, and one is very resistant to radiation,Deinococcus radiodurans. Both species were grownat ultra-low doses, at ordinary low doses in the realmof background, and at higher doses.

It is extremely difficult to remove radiation toultra-low levels because radiation is so pervasive. It’sin the building materials we live in, it’s in our food,our bodies, the air, soil and water, and in all laboratorymaterials and food that we feed to organisms in thelab.

So we built a laboratory 2,150 ft below the Earth’ssurface in the Waste Isolation Pilot Plant (WIPP) nearCarlsbad, New Mexico. WIPP is our only deepgeologic nuclear waste repository. It is in the middleof a 2,000-ft thick, stable, geologically-inactive250-million-year-old salt deposit that effectivelyshields cosmic and solar radiation (see figure above).

The laboratory is located in the north end of theunderground facility far away from any nuclear waste.Radiation levels here are 400 times below Earthsurface background levels, ironic given that this is a


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nuclear waste repository.

The radioactivity in this salt is extremely low becauseit is just NaCl, table salt, that contains almost nonaturally-occurring radioactive materials like uraniumthat occur in most rock, dirt, concrete and even wood.

In addition, we brought in an 8 ft x 6.5 ft x 6.5 ft vaultmade of 5-inch thick pre-World War II steel – steelwith no traces of radionuclides (see figure above).

Cells were grown in separate incubators in this vaultat 30°C (86°F) and 48% relative humidity. Cellsgrown under background radiation were subjected to100 nGy/hr(equivalent to 0.877 milliSv/year or 87.7millirem/year). Those grown under below-backgroundradiation were subjected to 0.2 nGy/hr (equivalent to0.0017 milliSv/year or 0.17 millirem/year), muchlower than any background level on Earth, and thelowest levels ever obtained in these types ofexperiments. (**see Note below for explanation ofthese units)

Three independent, replicated experiments wereconducted to study the effects of these two radiationdose rates on cell growth and gene expression. TheDNA sequence of genes monitored were those thathad previously shown significant patterns of up anddown regulation (turning on and off genes used torespond to the shock or stress of a biochemical insult)upon exposure to ionizing, UV and solar radiation.

When placed in the extreme below-background levelsof radiation, essentially zero radiation, growth wasinhibited in both species. Both species also showed ameasurable stress response, identifiable to specificgenes in their DNA, when in the absence of radiation(see figures below).


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Growth of bacteria is inhibited by the absence of radiation (400 times belowbackground levels), and is normal at background radiation levels, contrary tothat predicted by the traditional LNT hypothesis. OD = optical density ofbacterial cultures, a measure of growth. Source: Dr. Geof Smith, NMSU

Amazingly, those responses reversed when thebacteria were transferred back and forth to theopposite environments. The experiment usedreciprocal controls to verify that the physiologicalresponses observed were due to the radiationtreatment. By restoring background radiation levels toradiation-deprived cultures, the growth rate of bothspecies increased and the culture cell density returnedto that of the control after only 24 hours.

So, two species of bacteria from disparate taxonomiessensed and exhibited a physiological response to theabsence of radiation, indicating that these low levelsof radiation are a significant environmental cue. Andthe lack of radiation produced the substantial stress,not the presence of radiation.

These results contradict predictions of the LNThypothesis. The presence of radiation ins’t necessarilybad and the absence of radiation isn’t necessarilygood. I encourage you to read the complete paper fora detailed technical discussion. (This post is a bitgeeky, but it’s an important issue given Fukushimaand the growth of nuclear power).

Since life on earth evolved in the presence ofbackground radiation between 1 and 10 rem per year(0.01 and 0.10 Sv/year), it appears that life is adaptedwell to low doses of radiation and doesn’t do as wellin its complete absence.


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Stress-related genes in bacterial cultures are up-regulated (turned-on) to respondto the stress of having no radiation (400 times less than background levels).These same genes were down-regulated (turned-off) to respond to normal andeven higher levels of radiation (400 times greater than normal backgroundlevels) demonstrating the adverse effects of no radiation and the no-adverseeffect of having low doses of radiation. This figure includes new data, obtainedafter the Castille 2015 paper, at high background levels of radiation. If thetraditional LNT hypothesis were correct, these higher levels of radiation shouldturn on these stress-related genes, but they do not. Source: Dr. Geof Smith,NMSU

**Note: various pesky units are used to describeradiation dose. The U.S. unit for raw adsorbedradiation is the rad, and the international unit is theGray. 1 Gy = 100 rad. The U.S. unit for adsorbeddose relative to biological effects in humans is therem, and the international unit is the Sievert. 1 Sv =100 rem. For gamma radiation, Gy = Sv and rad =rem, so it’s easy to go back and forth. Unlike for alpharadiation where 1 Gy = 20 Sv and 1 rad = 20 rem.One measures rad and Gy directly, so these low-doseexperiments with gamma radiation are generallygiven in nanoGray (nGy or a billionth of a Gray),which is equal to a nanoSv (nSv) in this case.

Follow me on Twitter @jimconca and seemy book with Dr. Judith Wright at Amazon.com

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