Dialogue Not Debates About Cancer and Radiation Would Improve Disaster Preparedness

First of two blogs about low-level radiation and preparedness.

There was another polarized debate about the health effects of low-level radiation in October in the New York Times.

I have a hard time understanding the experts when they dig in. You wade through all this deep, depressing complexity, and if you don't give up, you are left with a leap of faith: radiation dose below 10 rem is a harmless crock - or the smallest amount will give you cancer.

That's why it took two months to write about it, and why I needed to: I'm not an expert. Just a participant.

Imagine what this learning curve must be like during a radiological disaster: rem stands for “roentgen equivalent in man”, and is a health measurement of the radiation dose absorbed by tissue. In most countries, this is called a sievert; 1 sievert is equal to 100 rem. Ten rem – the line in the sand for debating the chronic health effects from exposure to low-level radiation – is equal to 0.01 sieverts. 

A roentgen (R) is what a survey meter measures: it's a standard for the amount of radiation it takes to ionize one cubic centimeter of air. For gamma rays, the major initial product of a nuclear bomb or accident, 1 R is equal to 1 rem, and these terms are used interchangeably. But for high-energy alpha particles, like those produced by radon gas, 1 R is equal to 20 rem, since alpha radiation deposits twenty times more energy and so does twenty times more tissue damage than gamma.

It’s a hazmat & an SAT test. (Here is a good site about terminology and units.)

What is it about radiation dose that brings out the politician in the scientist? Uncertainty, said David J. Brenner of the Center for Radiological Research at Columbia University, writing in April of 2011 about the brand-new evacuation zones for Fukushima.

Cancer Risk From Low-Level Radiation Is “Educated Guesswork”, For Now

Brenner asks the fundamental question: how - after so many decades, after Hiroshima, Chernobyl – how can the long-term biological effects of low-level radiation still be so debatable?

Because you need to study too many people. Without them, no study can make an association strong enough to be broadly accepted by epidemiologists.

Since the average risk of getting cancer is so high – 40% - epidemiology is just not efficient at teasing out a small increase in cancer due to low-level radiation. Dr. Edouard Azzam and Dr. Roger Howell of the Rutgers NJ Medical School show (on slide 11) how many people would be needed in a study to be ninety percent certain of linking radiation dose with health effects. For an exposure of 100 rem, you would need about a thousand people; for 10 rem, you need almost a hundred thousand people. But for an exposure of one tenth of a rem (100 millirem), which one of the higher cleanup standards used by the Nuclear Regulatory Commission, you would need to study almost a billion people to be ninety percent sure of your conclusions.

Any study that links health effects to exposures lower than 10 rem but does not meet this gold standard is inherently preliminary, and debatable. What we are using in the meantime for regulatory purposes is a hypothesis, known as the Linear No-Threshold model.

Threshold or No-Threshold

The LNT model assumes that any dose of radiation, no matter how small, might give you cancer. There is no threshold - no dose - without a risk of cancer.

Data from research about the effects of radiation on atomic bomb survivors, was used to estimate what the proportional risk would be at lower levels, all the way down to zero. It assumes there is no efficient cell repair at any level that has evolved from our continual exposure to natural low-level radiation. The LNT model is an example of the precautionary principle: assume the worst until proven otherwise, when there is a suspected risk of causing harm to the public or the environment.

Below 10 rem is where the inference about risk is less tethered to the data, and consensus breaks up into camps. The ambiguity can be seen on one page of the Health Physics Society, a national organization of radiation safety professionals. The HPS states unequivocally that radiation doses “above about 10 rem … do increase the risk of developing radiogenic cancers following a latent period that may extend from 5 years to over 20 years. [But] It is not now known what the effects of doses below 10 rem might be.”

Then they leave the door open: “... it should be noted that although there is no direct evidence to indicate what effects low levels of radiation might have, there is substantial evidence supporting the idea that cancer may be initiated by a single gene mutation. There is also substantial evidence to suggest that the type of chromosomal damage caused by radiation is of a kind ([double strand breaks]) that is prone to errors during repair. There are also physical reasons why any radiation effect at very low doses should be proportional to the dose ...”

Because of this uncertainty, they support the LNT model, but in a very limited way - for regulation but not for prediction: “These indications, combined, suggest that LNT is a reasonable position, although it should be used with caution, especially in estimating numbers of deaths that may result from low-level radiation exposures. Such use is not justified by our current state of knowledge, nor is it justified by LNT. An unproven hypothesis may be useful in a pragmatic way to permit regulatory oversight, but not to arrive at quantitative conclusions about effects.” They emphasize that they do “not support the LNT model to calculate latent cancer deaths from low levels of radiation.”

Educated guesswork, for now.

What does 10 rem mean? One millionth of a rem is called a microrem. Natural background radiation in Monmouth County is around 10 micro roentgen per hour, so assuming for simplicity that roentgens and rems are equal, 10 rem is about a million times higher than our hourly exposure to radon and other natural radiation. One thousandth of a rem is called a millirem; the average yearly exposure to background radiation, medical tests, and consumer products is currently 620 millirem. Anyway you cut it, 10 rem – 10,000,000 microrem or 10,000 millrem - is a really big number to draw the doubt line. Perfect for opinions.

Ten roentgens also defines the lower boundary of the hourly dose produced in the Dangerous Fallout Zone after a 10 kiloton nuclear bomb is detonated. The DFZ is a potentially lethal region of radioactivity that briefly extends as far as twenty miles from ground zero. A ten kiloton bomb is the size chosen by federal planners for their hypothetical scenarios for terrorist attacks, and is about the size of the Hiroshima bomb.

Low-level radiation - below 10 rem - is where the major focus needs to be for disaster planning. It's what will affect the most people; it's what will let you back into your home. That's why the outreach needs to get much better, according to this 2010 article in in the New York Times, about the need to plan for the unthinkable without being fatalistic. So far the mainstream media has been better at this than government: two unlikely sources are a business webpage and a British tabloid.

So if epidemiology is stalled, where is progress? Molecular Biology research.

The second of two blogs about Low-Level Radiation and preparedness is at http://middletown-nj.patch.com/blogs/bill-simmonss-blog