**10. Miscellaneous observations and suggested further research**

The secondary photoelectron amplification of gamma radiation by different elements in living systems has importance in radiation dosimetry. For some inexplicable reason, elemental absorption has been entirely omitted from the calculations of absorbed dose published by radiation risk agencies like the International Commission on Radiological Protection (ICRP) which bases its recommendations of external dose limits on water- and tissue-equivalent phantoms. Furthermore, the phantom photoelectron radioactivity from this effect has considerable application to the element uranium which had been shown in a very large number of publications to have significant genotoxicity. This is particularly the case for internal uranium particles, generated from weapon use, from nuclear power station stacks, from global nuclear

**193**

*The Secondary Photoelectron Effect: Gamma Ray Ionisation Enhancement in Tissues from High…*

atmospheric testing, from nuclear fuel reprocessing and from uranium fuel manufacture. All the official risk agencies model uranium on the basis of its very low intrinsic alpha radioactivity and conclude that it cannot pose the risk that it clearly does. The basis for the current radiation risk model is the lifespan study of the Japanese A-Bomb survivors, the LSS. One major confounding exposure to the LSS cohorts, upon which the current risk model depends, was the post detonation black rain, which consisted of uranium particles from the weapons [44, 45]. On the basis of the arguments and evidence submitted in this chapter, the uranium particle exposures of all the different dose groups that have been used to construct a linear dose response make any attempt to use these data to define radiation risk unsafe. The unusual cancer results which emerged as soon as 1970 resulted in the researchers deciding to discard the not-in-city unexposed groups that are anomalously healthy. This was an error since these were the only groups not exposed to the black rain, although no doubt, the residual contamination will have caused inhalation exposures after they entered the cities, some months and years after the detonation. The issue was raised by Busby 2017 [45]. Studies of the LSS groups based on truly unexposed control groups in neighbouring prefectures carried out in 2009 showed that the cancer rates in all groups, especially the low-dose groups in the LSS cohorts,

What is being suggested here is that the entire understanding of gamma ray interaction with living tissue needs to be rethought. Research must be carried out to quantify the extent to which certain elements with high gamma and X-ray absorption coefficients bind to DNA and the extent to which this causes genetic and genomic damage at background levels and during radiotherapy or other external radiation situations. It is astonishing that no one has questioned the method that has been developed to assess harm from external photon radiations, the simplistic physics-based dilution of energy into water phantoms. It is not as if there was no evidence that this might be an unsafe approach. The radiosensitivity of the iodinerich thyroid gland should have supplied clues. The mechanism of the anticancer

High atomic number particles have increased in the environment in the last 50 years or more. Platinum particles emerge from catalytic converters, thorium particles emerge from gas light filaments and uranium particles are released from nuclear power stacks, reprocessing plants and many other sources. The high-Z secondary photoelectron effect is used in cancer therapy. There is a whole field of development here where anticancer agents may be synthesised to bind to DNA and

Finally, it is suggested that there is a simple experiment which will demonstrate and quantify this effect. It is to contaminate a system in which genetic damage may be measured with a uranyl salt, so that the DNA is contaminated with uranium, and then to irradiate the system with different doses of X-rays or gamma rays and then measure the genetic damage. To exclude alpha particle effects, the agent cisplatin

Although the sharp dependence of the gamma- and X-ray-induced photoelectron yield of elements on atomic number has been known for more than 100 years, the implications for radiobiology have been hardly addressed. This chapter aims to open up this issue and call for more research attention. First, it can be concluded that high-Z elements, when inside living tissue, represent a focus for absorption of photon radiation and that the resulting ionisation density close to the element

*DOI: http://dx.doi.org/10.5772/intechopen.86779*

were significantly high [46].

carry a high-Z warhead.

**11. Conclusions**

agent cisplatin should have supplied clues.

could also be employed in a similar experiment.

#### *The Secondary Photoelectron Effect: Gamma Ray Ionisation Enhancement in Tissues from High… DOI: http://dx.doi.org/10.5772/intechopen.86779*

atmospheric testing, from nuclear fuel reprocessing and from uranium fuel manufacture. All the official risk agencies model uranium on the basis of its very low intrinsic alpha radioactivity and conclude that it cannot pose the risk that it clearly does.

The basis for the current radiation risk model is the lifespan study of the Japanese A-Bomb survivors, the LSS. One major confounding exposure to the LSS cohorts, upon which the current risk model depends, was the post detonation black rain, which consisted of uranium particles from the weapons [44, 45]. On the basis of the arguments and evidence submitted in this chapter, the uranium particle exposures of all the different dose groups that have been used to construct a linear dose response make any attempt to use these data to define radiation risk unsafe. The unusual cancer results which emerged as soon as 1970 resulted in the researchers deciding to discard the not-in-city unexposed groups that are anomalously healthy. This was an error since these were the only groups not exposed to the black rain, although no doubt, the residual contamination will have caused inhalation exposures after they entered the cities, some months and years after the detonation. The issue was raised by Busby 2017 [45]. Studies of the LSS groups based on truly unexposed control groups in neighbouring prefectures carried out in 2009 showed that the cancer rates in all groups, especially the low-dose groups in the LSS cohorts, were significantly high [46].

What is being suggested here is that the entire understanding of gamma ray interaction with living tissue needs to be rethought. Research must be carried out to quantify the extent to which certain elements with high gamma and X-ray absorption coefficients bind to DNA and the extent to which this causes genetic and genomic damage at background levels and during radiotherapy or other external radiation situations. It is astonishing that no one has questioned the method that has been developed to assess harm from external photon radiations, the simplistic physics-based dilution of energy into water phantoms. It is not as if there was no evidence that this might be an unsafe approach. The radiosensitivity of the iodinerich thyroid gland should have supplied clues. The mechanism of the anticancer agent cisplatin should have supplied clues.

High atomic number particles have increased in the environment in the last 50 years or more. Platinum particles emerge from catalytic converters, thorium particles emerge from gas light filaments and uranium particles are released from nuclear power stacks, reprocessing plants and many other sources. The high-Z secondary photoelectron effect is used in cancer therapy. There is a whole field of development here where anticancer agents may be synthesised to bind to DNA and carry a high-Z warhead.

Finally, it is suggested that there is a simple experiment which will demonstrate and quantify this effect. It is to contaminate a system in which genetic damage may be measured with a uranyl salt, so that the DNA is contaminated with uranium, and then to irradiate the system with different doses of X-rays or gamma rays and then measure the genetic damage. To exclude alpha particle effects, the agent cisplatin could also be employed in a similar experiment.

#### **11. Conclusions**

Although the sharp dependence of the gamma- and X-ray-induced photoelectron yield of elements on atomic number has been known for more than 100 years, the implications for radiobiology have been hardly addressed. This chapter aims to open up this issue and call for more research attention. First, it can be concluded that high-Z elements, when inside living tissue, represent a focus for absorption of photon radiation and that the resulting ionisation density close to the element

*Use of Gamma Radiation Techniques in Peaceful Applications*

*Minimum concentrations of mineral elements essential for plants required for optimum growth as a function of the fourth power of the atomic number Z. The uranium data point is based upon detection of uranium in a* 

systems (blood, thyroid) are those which are clinically most sensitive to radiation exposure (for reasons which are clear from the discussions above). It was suggested that the reason why iodine was employed is that the element is being exploited for its radiation detection quality and that the thyroid mediates an induced radiation damage address system through upregulation of genes associated with cellular

Finally, the relationships discussed here also obtain for plants. Plants are unable to move to avoid radiation exposure and might be expected to reflect responses to evolutionary stresses. The relationship between atomic number and the optimum concentration of elements for plants to thrive has been shown to conform to the

same relationship [9]. The correlation is given in **Figure 13**.

**10. Miscellaneous observations and suggested further research**

The secondary photoelectron amplification of gamma radiation by different elements in living systems has importance in radiation dosimetry. For some inexplicable reason, elemental absorption has been entirely omitted from the calculations of absorbed dose published by radiation risk agencies like the International Commission on Radiological Protection (ICRP) which bases its recommendations of external dose limits on water- and tissue-equivalent phantoms. Furthermore, the phantom photoelectron radioactivity from this effect has considerable application to the element uranium which had been shown in a very large number of publications to have significant genotoxicity. This is particularly the case for internal uranium particles, generated from weapon use, from nuclear power station stacks, from global nuclear

**192**

**Figure 13.**

*wide range of plants [9].*

surveillance and repair [9].

### *Use of Gamma Radiation Techniques in Peaceful Applications*

is much higher than what is calculated using conventional dosimetry such as that employed in current radiation protection, as in, e.g. [41]. This effect, the secondary photoelectron effect (SET), is most relevant to elements which also have affinity for DNA, the target for radiation-induced genotoxicity. The intrinsic radioactivity of such elements is not relevant, as can be seen by the genotoxicity and cancer therapy effect of the drug cisplatin. Results of Monte Carlo modelling carried out at the University of Ulster show that internalised high atomic number nanoparticles are likely to cause high local ionisation in living tissue. These effects are greatest for low-energy photons such as those in the natural background radiation spectrum. It is suggested that this may be one explanation for the anomalous genotoxicity of uranium particles found in many studies but hitherto dismissed as radiation effects on the basis of conventional dosimetry. Finally, an examination of the spectrum of elements employed by living systems reveals an interesting relationship which correlates the elemental composition adopted by life itself with the photoelectron cross section of the elements available to evolution. This relationship, which follows the photoelectron cross section and is highly statistically significant, suggests that living systems are exquisitely and critically sensitive to ionising radiation and have had to develop throughout evolution in such a way as to minimise the ionisation damage induced by background radiation. There are many important consequences of this approach, but the main ones are in the area of radiation risk assessment and in cancer therapy. Some approaches and experiments are suggested.
