BIOLOGICAL DAMAGE FROM MEDICALRADIATION
As a physician, I took the Hippocratic Oath: “First, do no harm.” My silence about these issues would contribute to the harm of millions of people. Why wait? What is the purpose?
The biological damage from a medical x-ray procedure does not come directly from the x-ray photons. The damage comes from electrons, which those photons “kick” out of their normal atomic orbits within human tissues. Endowed with biologically unnatural energy by the photons, such electrons leave their atomic orbits and travel with high speed and high energy through their home cells and neighboring cells. Each such electron gradually slows down, as it unloads portions of its biologically unnatural energy, at irregular intervals, onto various biological molecules along its primary track (path).
The molecular victims include, of course, chromosomal DNA, and the structural proteins of chromosomes, and water. Even though each energy-deposit transfers only a portion of the total energy of a high-speed high-energy electron, the single deposits very often have energies far exceeding any energy-transfer which occurs in a natural biochemical reaction. Such energy-deposits are more like grenades and small bombs.
The Free-Radical Fallacy
There is no doubt that, along the path of each high-speed high-energy electron described above, the energy-deposits produce various species of free radicals. Nonetheless, it is a demonstrated fallacy to assume equivalence between the biological potency of x-rays and the biological potency of the free radicals which are routinely produced by a cell’s own natural metabolism. The uniquely violent and concentrated energy-transfers, resulting from x-rays, are simply absent in a cell’s natural biochemistry. As a result of these “grenades” and “small bombs,” both strands of opposing DNA can experience a level of mayhem far exceeding the damage, which metabolic free-radicals (and most other chemical species) generally inflict upon a comparable segment of the DNA double helix.
Ionizing Radiation: A Uniquely Potent Mutagen
The extra level of mayhem is what makes x-rays (and other types of ionizing radiation) uniquely potent mutagens. Cells cannot correctly repair every type of complex genetic damage, induced by ionizing radiation, and sometimes cells cannot repair such damage at all. Not all mutated cells die, of course. If they all died, there would be very little cancer and no inherited afflictions. Indeed, certain mutations confer a proliferative advantage on the mutated cells.
Exposure to x-rays is a proven cause of genomic instability — – a characteristic of many of the most aggressive cancers. Unlike some other mutagens, x-rays have access to the genetic molecules of every internal organ, if the organ is within the x-ray beam. Within such organs, even a single high-speed high-energy electron, set into motion by an x-ray photon, has a chance (far from a certainty) of inducing the types of damage which defy repair. That is why there is no risk-free (no safe) dose-level.
There is widespread agreement that, by its very nature, ionizing radiation at any dose-level can induce particularly complex injuries to the genetic molecules. There is growing mainstream acknowledgment that cellular repair processes are fallible, or entirely absent, for various complex injuries to the genetic molecules.
The Very Low Doubling-Dose for X-ray-Induced Chromosomal Mutations
The inability of human cells, to repair correctly every type of radiation-induced chromosomal damage, has been demonstrated in nuclear workers (who received their extra low-dose radiation at minimal dose-rates) and in numerous studies of x-ray-irradiated human cells at low doses. Besides demonstrating non-repair or imperfect repair, such studies have established that x-rays have an extremely low doubling-dose for structural chromosomal mutations. (The doubling dose of an effect is the dose which adds a frequency equal to the preexisting frequency of that effect.)
For instance, the doubling-dose for the dicentric mutation is in the dose range delivered by some common x-ray procedures, such as CT scans and fluoroscopy — i.e., in the dose range of 2 to 20 rads. The rad is a dose-unit which is identical to the centi-gray. We, and many others, prefer the simpler name: Rad. X-rays are capable of causing virtually every known kind of mutation — from the very common types to the very
complex types, from deletions of single nucleotides, to chromosomal deletions of every size and position, and chromosomal rearrangements of every type. When such mutations are not cell-lethal, they endure and accumulate with each additional exposure to x-rays or other ionizing radiation.
Medical X-rays as a Proven Cause of Human Cancer
Ionizing radiation is firmly established by epidemiologic evidence as a proven cause of almost every major type of human cancer. Some of the strongest evidence comes from the study of medical patients exposed to x-rays — even at minimal dose-levels per exposure.
Mounting mainstream evidence indicates that medical x-rays are 2 to 4 times more mutagenic than high-energy beta and gamma rays, per rad of exposure.