Thursday, June 2, 2011

Radiation and Health - The Gray Areas

Linear no threshold modeling is a commonly used and commonly criticized method for determining the effect of something on something else. Radiation's impact on health is commonly calculated by the linear no threshold method. There is nothing particularly wrong with using this method as a part of an analysis. It provides a reasonable upper bound for the relationship of radiation to health.

With radiation, the main concern is long term cancer risk. Does exposure to x amount of radiation at y age produce z more cancers. There are more interesting parts of the puzzle.

Medicine has made a lot of advances in the past couple of hundred years. The average life expectancy at birth has increased from say 40 years to nearly 80 years since the late 1800's. Small pox, polio, measles, influenza, malaria and many other maladies have been eliminated or more easily controlled in most regions. In comparison only a few other new maladies have been cropped up but some older maladies have increased.

Cancer was virtually unknown in the 1800's. Between all the other causes of death, cancer took too long to become apparent and medical science was not up to speed in determining the exact cause of death. Autopsies were pretty uncommon due to religious belief and limits on preserving the dead long enough to do autopsies.

I know this is pretty macabre, but people only live so long. Average life expectancy doubled, but a constant doubling is unlikely. 120 years appears to be about the maximum life expectancy. Getting the average to approach the maximum is going to be harder and harder as science advances.

Since 1950, the average live expectancy has increased greatly and the percentage of death due to cancer has as well. Some of the cancer increase is due to man made radiation but realistically, the majority of the cancer increases is due to medical advances decreasing deaths by other causes.

How the other causes of cancer rate increase is dealt with greatly impacts the results of linear no threshold modeling. To be honest, it is only in the past 20 years or so that we have developed the tools to even begin to determine the different causes with human genome mapping (DNA testing).

Recent studies have found that cellular telephone use may possibly be linked to brain cancer. The media picked up part of the studies that indicate people that have used cell phones for 10 years or more have twice the occurrence of a pre-cancerous brain condition. Twice what and when will it be cancer? Dunno. Will technology increase the risk of other types of cancer and diseases? Of course. But if we eliminate the technologies that lead to the increased risk we increase the risk of something else. For example, without cellular phones, the risks due to inadequate warning of sever weather, fire and a variety of other things could more than offset the health gains of not having cell phones that may possibly cause brain cancer. There is no need to eliminate cell phones, just be aware of the possibilities and adjust your use responsibly. Manufacturers will probably add a little extra radiation barrier between the microwave source and the speaker or more people will get ear pieces which have a different potential health impact. It is a learning curve thing.

Too much sun leads to skin cancers which can evolve into other cancers. Stay out of the sun or use more sunscreen. But a certain amount of sun is good for other health reasons and gradual increases in sun exposure seems to reduce the potential of skin cancer, the radiation paradox.

Some where there is an optimum balance that increases life expectancy. I am a proponent of nuclear energy because there is an optimum balance were some increase in risk of radiation hazard offsets other risks. Life is full of trade offs.

This brings me back to linear no threshold modeling. While it is a valid statistical method, it tends to over emphasize the risks of one aspect while not illustrating the big picture. Studies by Green Peace and other non-governmental agencies tend to overly emphasize their cause, muddying the overall picture. Not that there is no validity to their work, just that their lack of objectivity biases their results.

It is frustratingly similar in climate science. Man does appear to have an impact on climate. That impact is due to a variety of activities, some of which are more easily modified and others that require a shift of risk factors. Increasing nuclear energy use has its risks, changing economic conditions has risks and changing political power structure has risks.

The change in climate may improve overall conditions. We are adapted to current conditions, so we accept current risks. A changed climate may include rewards, but also may include new risks. To determine a best plan of action or inaction, we need to better understand the possibilities and basically chose the preferred type of life and death for us and future generations. Scary thought.

Some groups are confident that their plan for the future will produce the near optimum future world. Personally, I am not arrogant enough to believe my vision is better. I am fairly confident that actions that blend risks wisely are a good way to hedge against stupidity. So when I look at future energy options, I lean toward what I envision are responsible compromises.

Nuclear energy is a large part of my vision. Smaller, more widely dispersed nuclear power plants tend to reduce risk and increase availability and increase shared risk. Alternate energies like wind, wave and solar also are best dispersed to allow for shared risk.

Yes, even "clean" energies have risks. After manufacture, solar photovoltaic panels are pretty low risk, but the chemicals used in their manufacture are not without risk. Wind power is clean, but you have the risk involved with the chemicals and pollutants during manufacture, some environmental risks where the wind turbines are installed and the risk of no power at critical times.

The no power at critical times is a risk I believe is under emphasized. Over reliance on any one form of energy increases that risk. Huge mega power plants increase risks not only locally, like Fukushima, but nation wide. Distribution infrastructure is overly taxed when a large power plant goes off line increasing the risk of black outs or brown outs which are risks because our societies are dependent on the near uninterpretable sources of energy. A relatively short blackout of a few days in a large metropolitan areas causes deaths.

Over reliance on petroleum products also is a great risk as many societies depend on that source of easily available energy. Societies that have less dependence on fossil fuels also have shorter average life spans.

Secure energy and energy security sound the same but are different. Energy security reduces risks by reducing dependence on other societies which may have different visions. Secure energy reduces self inflicted risks. So instead of thinking about your favorite energy options as being sustainable, cheap or profitable you should add secure. That would make you more inclined to accept a mix of options instead of arrogantly assuming your vision is perfect. While there may be a perfect energy source, it is pretty unlikely. If you feel that all energy is evil, maybe you should try to realize that is also pretty unlikely.

If you can objectively look at energy sources, you may find that linear no threshold evaluation of nuclear energy is properly criticized because it discounts the overall benefits for the sake of minimal increased risk.

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