Mesothelioma Information - Causes of Mesothelioma
Response to Low-Dose Radiation
The activity of the DNA damage control biosystem is decreased by high-dose radiation, but adaptively responds with increased activity to low-dose radiation.
9, 22,23,26-33 The efficiency of this biosystem is increased by the adaptive responses to low-dose ionizing radiation .This is well documented in UNSCEAR 1994:4 "There is substantial evidence that the number of radiation-induced chromosomal aberrations and mutations can be reduced by a small prior conditioning dose in proliferating mammalian cells in vitro and in vivo. There is increasing evidence that cellular repair mechanisms are stimulated after radiation-induced damage... Whatever the mechanisms, they seem able to act not only on the lesions induced by ionizing radiation but also on at least a portion of the lesions induced by some other toxic agents. As to the biological plausibility of a radiation-induced adaptive response, it is recognized that the effectiveness of DNA repair in mammalian cells is not absolute...
An important question, therefore, is to judge the balance between stimulated cellular repair and residual damage." This statement applies not only to the mutations produced by radiation and other toxic agents, but also to the unmentioned enormous number of daily metabolic mutations. The operative effect of reducing metabolic mutations by the adaptive response of the DNA damage-control biosystem to low-dose radiation is the critical factor, not reduction of the relatively negligible number of mutations produced by low-dose radiation. This critical factor must be considered, "to judge the balance between stimulated cellular repair and residual damage." Assuming a 20% increased efficiency of biosystem control in response to a tenfold increase of annual background radiation from 0.1 cGy/y, to 1 cG/y, radiation mutations would indeed increase from 1x10-7/cell/d to 8x10-7/cell/d but metabolic mutations would decrease from 1/cell/d to 0.8/cell/d (Figure 11).17
"The balance between stimulated cellular repair and residual damage" is a decrease of mutations from an average of 1 mutation/cell/d to 0.8 mutation/cell/d UNSCEAR did not consider that the increase of radiation mutations is negligible compared to the operative effect of the adaptive response to low-dose radiation upon the high background of metabolic mutations. The biologic effect of radiation is not determined by the number of DNA mutations it creates, but by its effect on the biosystem that controls the relentless enormous burden of oxidative DNA damage.
High-dose radiation impairs this biosystem with consequent significant increase of metabolic mutations and corresponding risk increments. Low-dose radiation stimulates the DNA damage-control biosystem with consequent significant decrease of metabolic mutations and corresponding risk decrements (Figures 8-11).35 This reduction of gene mutations in response to low-dose radiation provides a biological explanation of the statistically significant observations of mortality and cancer mortality risk decrements, and contradicts the biophysical understanding of the basic mechanisms upon which, ultimately, the NCRP's confidence in the LNT hypothesis is based. This article represents the views of the author and not necessarily those of the U.S. Nuclear Regulatory Commission.
Mesothelioma Information
There are three distinct types of mesothelioma, each affecting a different section of mesothelial tissue. The three types of mesothelioma are pleural mesothelioma, peritoneal mesothelioma and pericardial mesothelioma.
Mesothelioma treatment options have provided very limited success in combating the fatal disease.