Low Dose Radiation and Genetics

Philip Carlson MD
Radiology Professor Emeritus, University of Wisconsin

The human cell is an amazing entity that has evolved over millennia developing remarkable protective and healing capabilities.  All life on earth has evolved in a very hostile decreasingly radioactive world. As a survival response our cells have developed genetic reparative enzymes to fix the single and double stranded DNA breaks that occur, due not only to external radiation, but also to our own internal radiation in the form of the food and liquid we eat and drink.

But ionizing radiation is not the only culprit causing DNA damage.  In fact, it is a tiny fraction of that caused by the major culprit, that being naturally produced physiologic ionized oxygen molecules (commonly known as free radicals of oxygen) within our bodies which actually account for at least 10000 DNA breaks per cell per day.  One study from MIT (referenced below) detected no additional DNA breaks in mice with chronic background radiation of 400 times normal.  Our DNA reparative enzymes are highly efficient at repairing this damage and actually improve in their capabilities when exposed to low doses of radiation, a process called adaptive response.  Indeed, background radiation levels around the world are highly variable (see following table) with no secondary discernable adverse change in cancer rates.

 Annual Background Radiation Level

By Location

Madison Wisconsin               3.5 mSv per year

Denver Colorado                   7.5 mSv per year (proximity to thorium/uranium in rock)

United Kingdom                    2 mSv per year

Finland                                   8 mSv per year

Guarapari Beach Brazil         175 mSv per year  (proximity to thorium in sand)

Ramsar Iran                           250 mSv per year  (proximity to radium springs and limestone)

For these reasons we need not fear chronic low doses of radiation within our food, our environment, while flying, or at the doctor’s office!  Our DNA reparative enzyme mechanisms are very capable of rapidly reversing genetic damage over a broad range of background radiation levels.

The 3 conclusions, then, that we can draw from this article are:

  1. Human beings and all life have evolved in a decreasingly radioactive environment over the millennia and have developed extremely efficient physiologic mechanisms to repair genetic damage.
  1. Genetic damage caused by chronic background and dietary radiation is a miniscule fraction of the total genetic damage we experience every minute of every day.The major cause is our own internal natural physiologic ionized oxygen molecules reacting with our DNA.  The MIT study cited showed NO increase in DNA breakage in mice exposed to 400 times normal background radiation levels.
  1. There is no need to fear low dose radiation.It has even been shown by multiple studies that it stimulates the cellular enzymatic DNA repair capability.  This is called adaptive response.

References

Radiation:  The Facts by Robert Hargraves and included citations at http://Radiation-Safety-Limits.info

Integrated Molecular Analysis Indicates Undetectable Change in DNA Damage in Mice after Continuous Irradiation at 400-fold Natural Background Radiation:  Olipitz et al:  Environmental Health Perspectives, April 26, 2012

Health Physics Society, 2010