# Low Dose Ionising Radiation-Induced Hormesis: Therapeutic Implications to Human Health
## 2 LDIR-Induced Detrimental Effects  
In contrast to earlier findings on the bio-positive effects of LDIR, in recent decades, inconsistent and conflicting findings and contradictory data have by default lead to support for the LNT theory. High doses of ionising radiation are harmful to humans and all other living organisms, resulting in a high local yield of unrepaired base damage and unrepairable, complex double strand breaks (DSBs) that result in chromosome aberrations, mutations, cell apoptosis, senescence, and carcinogenesis [34; 35]. The known risks of such radiation exposure have rightfully restricted the use of ionising radiation except when used under proper guidelines and regulations of authoritative organisations, controlled for example in medical applications, including X-ray imaging and radiotherapy treatments. Within this, the potential detrimental health effects of LDIR exposure in medical diagnostics and treatments are also treated as being of major concern; this is reflected in the overarching need to ensure that the benefits far outweigh the risks.  
A pilot study in occupational exposure to LDIR among medical radiology staff has reported results of cytokinesis-block micronucle assay and comet assay, showing a higher frequency of nuclear buds and tail length, respectively, among medical workers compared to the control group. At levels of 1.82 \(\pm\) 3.60 mSv/year, the results indicated poor cytogenetic status and an increase in DNA damage following long-term exposure to LDIR [36]. In another study [37] concerning patients undergoing neuro-interventional radiological procedures, it was reported that this gave rise to an increased risk of DNA damage, as demonstrated by yH2 AX and p53 Ser15 phosphorylation. The associated levels were found to be increased in peripheral lymphocytes following exposure to relatively low surface entrance doses (9 to 225 mGy), also with DNA damage being influenced by age, fraction  
Figure 2: The molecular mechanisms and the cellular responses of low dose ionising radiation.  
and a sub-population of lymphocytes (variable gene expression pattern) and repair kinetics among individuals. The study also made it clear that, balanced against the potential harmful radiation effects, patients greatly benefit from such procedures. At the same time, it was advocated that the use of ionising radiation in medical diagnosis purposes be carried out at the lowest possible radiation doses, not compromising diagnostic capability [37]. Indeed, many other studies have reported similar findings, not least concerning the occupational low dose exposures to ionising radiation, especially in healthcare workers. Reports have been concerned with long-term and adverse health effects, including increased levels of inflammatory cytokines, increased micronuclele frequency, reduced antioxidants and increased mitochondrial DNA4977-bp deletion [38; 39; 40]. These apart, several lines of evidence also suggest that there are negative biological effects of LDIR in cells and animal models. Low-dose ionising radiation has been demonstrated to affect innate and adaptive immune responses by attenuating mast cell migration through inhibition of monocyte chemoattractant protein-1 (MCP-1) expression by Nr4a2 [41]. Figure 2 shows the molecular mechanisms and the cellular responses of LDIR-induced detrimental effects.