AbstractThe increasing use of technology continues to draw persistent debate on its safety on human health and the environment.
With the world experiencing potential effects of globalization, the use of mobile telephony and other radiofrequency (RF)-emitting equipments have been designed to enable man become more efficient in his business dealings and social life in general. The extensive use of these equipments has caused an increasing public health concern on the effects of RF electromagnetic fields exposure(SECNIHR, 2009). However, there have been conflicting experimental results made in publications on the teratogenic, carcinogenic and mutagenic effects of RF electromagnetic fields. It has also been found out that the overwhelming research findings do not provide sufficient evidence on the assumptions that the exposure to RF really induces carcinogenic, teratogenic or mutagenic effects (SECNIHR, 2009). Matters related to human health should be taken seriously and qualitative and quantitative research needs to be carried out with rigor. Therefore, the health effects resulting from low level exposure to RF require further study. This paper explores possible health effects brought by increased RF exposure and attempts to demystify the unfounded fears on the use of RF emitting equipments.
Radio Frequency EnergyIntroduction Radio frequency (RF) is a collective term for electromagnetic radiations which consist of magnetic and electric energy waves that move together at a very high speed (the speed of light) through space. The electromagnetic energy or electromagnetic spectrum consists of microwaves and radio waves as examples. These spectrums are produced by transmitting antennas and are collectively known as radiofrequency radiation or energy. RF emitting equipments continue to be used extensively in the world today.
The frequency band for RF emitting equipments is 100 kHz < f ? 300 GHz (SECNIHR, 2009). The highest human absorption of RF energy is within the RF frequency range of approximately 70 MHz (SECNIHR, 2009). At this frequency range, the rate of RF energy absorption is at the maximum. This rate is known as the specific absorption rate (SAR) and is expressed in watts per kilogram or W/kg (SECNIHR, 2009). Because of this established range where human absorptions are highest, the standards of RF safety have restricted exposures between 30-300 MHz (SECNIHR, 2009). The common sources of RF energy include mobile telephones, medical, broadcasting as well as industrial applications equipments.
While the information on the emissions which arise from RF equipments is sufficiently available, the information on individual persons’ exposure is poorly understood and documented. The information on human exposures to RF energy is critical to carry out epidemiological studies (Kundi, 2005). The need to optimize the assessment methodologies of individual exposures emerges to be the other important reason for understanding human exposures to RF energy field (ICNIRP, 2004). The information on human RF exposures will also be important in the proper use of the existing exposimeters or further developing accurate exposimeters to avoid unfounded fears of the use of RF emitting equipments.Biological Effects of RF Exposure Exposure to very high RF energy can lead to significant biological effects in humans which can be harmful to health. The biological effects of RF energy mainly result from tissue heating commonly known as thermal effects (Kundi, 2005).
For many years, negative effects of very high RF exposures to human health have been known because the RF energy has a potential to heat up biological tissues at a fast pace. Unfortunately, this principle has been exploited by microwave technology to heat up foods quickly using microwave ovens. These exposures to very high intensities of RF energy can pose potential harmful effects because of the ability to heat up biological tissues and rapidly cause the rise of body temperature or hyperthermia.
The testicles and the eyes are the most vulnerable body parts to heating by RF energy (ICNIRP, 2004). These body parts lack sufficient blood flow that can dissipate the excessive heat from them. While exposures to very high RF energy can cause significant body tissue heating, low RF energy exposures have not been shown to cause any harmful effects to biological tissues. Some of the studies that have been carried out by other researchers indicate the link between RF exposures and headaches in humans (Chia, Chia & Tan, 2000). Since studies that have been done are based on in vitro experiments, the data has been difficult to be reproduced in human subjects. It has been concluded that the RF energy exposures that are routinely encountered by the public are far much below the known levels that may cause serious hyperthermia and general heating. There is therefore need to carryout extensive research to determine the relevance of RF exposure to human health.RF and Human Cancers The Scientific Committee on Emerging and Newly Identified Health Risks (SECNIHR) published a report in 2007 making conclusions that animal experiments, in vitro and epidemiological human studies poorly supported that RF energy field exposures resulted to any significant increase in human cancers (SECNIHR, 2009).
There have been a number of published studies that have specifically focused on the carcinogenic effects of RF exposures in humans (Kundi, 2004). These studies made by Michael Kundi and other researchers concluded that human RF exposures especially mobile phone users were at a higher risk of developing neoplastic diseases or cancers (Kundi, 2004). However, other studies have made publications that have immensely contradicted Kundi and other researchers’ study that purported the potential carcinogenicity of RF exposures. These publications have maintained that no study results have so far given convincing and consisted evidence over the relationship between adverse health effects and RF exposures (SECNIHR, 2009).Previous speculations by the SECNIHR maintained that long exposures to RF energy particularly among mobile phone users caused neoplastic diseases. However, these speculations were limited since not many people have used mobile phones for a period exceeding ten years. Although a number of studies have then been published about the carcinogenesis of RF exposures particularly among mobile phone users, the SECNIHR assessments still remain valid and the link between RF exposures and carcinogenicity cannot be firmly established (Scientific Committee on Emerging and Newly Identified Health Risks, 2009).
The World Health Organization in 2006 provided critical information on the link of base stations and various wireless technologies on the cause human cancers. In the report, the WHO made conclusions that scientific evidence on cancer distribution among populations does not support evidence that RF exposures from base stations increase the risk of developing cancer (WHO, 2006). Similarly, according to the WHO, animal experiments have failed to provide significant proof to show the link between RF exposures and carcinogenicity even when levels of exposures of 4W/kg higher than those emitted by wireless networks and base stations are used (WHO, 2009). While little experimental data have shown some possible correlation between RF exposure and development of cancers in animal studies, these results have not be able to be replicated independently and some studies have completely failed to show this correlation.
RF and Genotoxicity Critics have suggested that exposure to RF energy has a potential of causing genotoxicity or defects in the genetic material of humans. In this aspect, the observers imply that the exposure to RF energy can cause changes in the structure of DNA and result to mutations. In a report published by the SECNIHR, the evidence on the relationship of RF exposures and genotoxicity is poorly supported. The SECNIHR claims that in vitro studies have shown that there is no link between DNA damage and RF exposures (Kundi, 2005).
Evidence from work done by different researchers working on Drosophila melanogaster have shown that there is a reduction in the capacity of the flies to reproduce effectively. However, these experiments have utilized RF ranges of between 900 to 1800 MHz which are far much higher than the ranges emitted by wireless equipments and other RF emitting equipments (SECNIHR, 2009). In vitro studies that have been conducted using human spermatozoa have utilized RF ranges of 1.8 GHz and the SAR of up to 27.
5 W/kg (SECNIHR, 2009). While these experiments have shown significant reduction in vitality and motility of human sperms, the frequency range used is exaggeratingly higher than what humans get exposed to. The usual SAR is set at 1.
6 W/kg according to the Federal Communication Commission (FCC). At these frequencies, the human sperms present markers of 8-oxo-2’-deoxyguanoosine, undergo oxidative stress, have increased fragmentation of DNA and have a stimulated formation of DNA base adduct (SECNIHR, 2009). Therefore, this shows that the claims made that RF exposures may cause genotoxicity in humans do not reflect the ranges of exposures in real life. Experimental studies should be done while considering the range of human exposure in his natural environment. The ranges of 1.
8 GHz are not practical with the commonly used RF emitting equipments at homes and offices (SECNIHR, 2009). This is indicative that the RF exposures are not genotoxic and all the studies which have shown positive effects have questionable experimental deficiencies.Other non-genotoxic effects of RF exposures have been investigated. These investigations have benefited from the induction of various cellular processes as well as molecular and metabolic changes.
Cellular processes that have been exploited in the study of non-genotoxic effects of RF exposures include the induction of apoptosis or cell death. There have been conclusions that RF exposures cause the active release of singlet oxygen or reactive oxygen species (ROS) ion experiments where 1.8 GHz human epithelial cells were exposed to SAR of up to 4W/kg (SECNIHR, 2009). Other effects observed due to this exposure include cell arrest and massive release of intracellular singlet oxygen.
However, when these experiments were repeated and DNA damaging effects blocked by superposing the cells with electromagnetic noise of 2 µT, these effects were greatly reduced (ICNIRP, 2004). This led to researchers making conclusions that the massive production of singlet oxygen was as a result of DNA damage that was induced during earlier experiments. Even though exposure of some cells to RF energy caused significant apoptosis, these experiments could not be replicated in cultured neurons extracted from embryonic cerebral cortical cells from Wistar rats (SECNIHR, 2009). Human trophoblast cells exposed to 1817 MHz sinusoidal RF electromagnetic waves gave poor results in the studies of stress induction of RF exposures. In other human studies, it was reported that 1.3 W/kg human exposures to mobile phones resulted to an alteration of some human skin proteins (SECNIHR, 2009). The biological significance of these studies fails to convincingly contribute to conclusions that RF exposures lead to human health problems. This is because in experiments that used 1,200 candidate genes from rat neurons controlling metabolism, pathways of signal transduction and cytoskeleton showed that only 24 of these genes being up-regulated and only 10 of the genes being down-regulated after an average SAR exposure of 2 W/kg (SECNIHR, 2009).
These experiments provide evidence that RF exposures do not have significant effects on gene expression and general gene function.RF and the Nervous System Effects Some studies have purported that RF exposures cause a number of harmful effects on the nervous system. However, SECNIHR made conclusions on its 2007 opinion that RF exposures had no significant neurotoxic effects to humans (SECNIHR, 2009). While certain biochemical and electrical changes have been observed in neurotransmission, these changes do not suggest any significant pathological condition.
The stress conditions that have been observed in animal experiments do not actually arise from RF exposures but from the human induced stress on the way they handle the animals during experiments. For this reason, there have been suggestions to reduce the effects of stress in future animal experiments investigating cognitive abilities among restraint animals. SECNIHR (2009) conclude that while a few findings, and of course negative studies, have suggested the possibility of the effect of RF exposures on the nervous system, there is still not any conceivable evidence to show that acute and long-term exposures to RF equal to the levels emitted by mobile phones actually show negative effects to cognitive abilities in both animal and human studies. However, human EEG studies have shown some evidence on the effect of RF exposures on the brain activity. Among these studied effects include the interruption of sleep as well as the parameters of sleep EEG.
The SECNIHR maintain that some of these findings contradict in concepts and are not supported by extensive studies in cellular activities and cellular mechanisms. There is therefore a need to expand these studies into accurate and scientific mechanisms able to provide concrete explanations on EEG studies in relation to sleep. At the same time, no evidence have been provided to show the effects of RF exposures on vision and hearing and no direct evidence to show the neurotoxicity of RF exposures in humans. While gliosis in activated cells has been shown in slightly higher SAR values, there has not been seen any neurodegeneration at normal or low-level exposures common to most RF emoting equipments used by most individuals.Conclusion There have been repeated animal and human in vitro studies to confirm the possible health effects that may result from RF exposures. While these studies provide positive results on the genotoxic, mutagenic, carcinogenic and teratogenic effects of RF exposures, the RF ranges used in these experiments are usually higher than the standards set for RF human exposures in equipments such as mobile phones.
The reproductive and developmental effects of RF exposures have been identified but still these studies are far from convincing that the RF ranges used reflect the normal human exposures to RF electromagnetic energy. In general, there is no epidemiologic evidence to show that RF exposures especially among mobile phone users who have used phones for a period not exceeding 10 years cause acoustic neuroma or any brain tumors. Studies of longer exposures, more than 10 years have also failed to support claims that RF exposure cause tumors although there have been evidence on the link between RF exposures and acoustic neuroma.
Non cancer studies of RF exposures have also failed to provide conclusive evidence. Studies on RF exposures link to headache, dizziness, and fatigue and attention disorders have not been supported with epidemiological data. At the same time, reproductive and neurological effects of RF exposures fail to reflect the range of exposure limits as specified by the International Commission on Non Ionizing Radiation Protection (ICNIRP).
In general, there are no health effects that have consistently been demonstrated at ICNIRP exposure level limits. Although present studies have shown little correlation between RF exposure and health effects, long-term studies should be done and provide conclusive report on this subject matter. These studies will be important in demystifying numerous false theories surrounding this subject and allow conducive environment for the use and expansion of technology.References:Chia S. E, Chia H. P & Tan J.S (2000). Prevalence of headache among handheld cellular telephone users in Singapore: a community study.
Environmental Health Perspectives. 108:1059–1062Kundi, M (2005). Epidemiology of health effects of radiofrequency exposure. Environmental Health Perspective.113 (3):A151Kundi, M (2004). Mobile phone use and cancer. Occupational and Environmental Medicne.
61 (6): 560-570.ICNIRP (2004). Epidemiology of health effects of radiofrequency exposure. Environmental Health Perspectives. 112 (17): 1741-1754.SECNIHR (2009).
Health Effects of Exposure to EMF. Retrieved July 26, 2010 from, http://ec.europa.eu/health/ph_risk/committees/04_scenihr/docs/scenihr_o_022.pdfWHO (2006).
Electromagnetic fields and public health. Retrieved July 26, 2010 from, http://www.who.int/mediacentre/factsheets/fs304/en/