Radiofrequency radiation: A possible threat to male fertility

Highlights

• Excess exposure to RFR emitting devices may alter sperm parameters.

• Oxidative stress and PKC could be the possible mediators of RFR action.

• Few compounds found to reverse the effect of RFR on male germ cells.

Abstract

Radiofrequency exposure from man-made sources has increased drastically with the era of advanced technology. People could not escape from such RF radiations as they have become the essential part of our routine life such as Wi-Fi, microwave ovens, TV, mobile phones, etc. Although non-ionizing radiations are less damaging than ionizing radiations but its long term exposure effect cannot be avoided. For fertility to be affected, either there is an alteration in germ cell, or its nourishing environment, and RF affects both the parameters subsequently, leading to infertility. This review with the help of in vitro and in vivo studies shows that RF could change the morphology and physiology of germ cells with affected spermatogenesis, motility and reduced concentration of male gametes. RF also results in genetic and hormonal changes. In addition, the contribution of oxidative stress and protein kinase complex after RFR exposure is also summarized which could also be the possible mechanism for reduction in sperm parameters. Further, some preventative measures are described which could help in reverting the radiofrequency effects on germ cells.

Introduction

Radiations are the energy with wave properties having a magnetic field and an electric field. It can be divided into two types: ionizing and non-ionizing radiations. Ionizing radiations like x-rays, gamma rays, and alpha particles are more injurious than non-ionizing radiations. They can break chemical bonds and induce DNA damage. Non-ionizing radiations do not have enough energy to break chemical bonds. Non-ionizing radiations can be further characterized into 1) Extra-low frequency (ELF) 2) Radiofrequency (RF). ELF includes electromagnetic radiations from 1 Hz to 300 Hz. Power lines and electrical equipments produce ELF at 60 Hz [1]. These ELFs might have an association with an increased cancer risk, as stated by some epidemiological studies [2,3]. Radiofrequency EMR is a transmission of energy through radio waves with range varying from 3 kHz to 300 GHz. Radiofrequency radiation is produced by FM radio (88−108 MHz), TV (50−700 MHz), cell phones (850−2.4 GHz), Wi-Fi & microwave ovens (2.4 GHz), radar (1−100 GHz), etc. (Fig. 1) [1]. Exposure to high RF-EMF levels induces an electric field into the body and exerts a force on free-moving electrons, ions and, polar molecules (e.g., water molecules) and, EMF gets converted to kinetic energy. As a result of it, these charged molecules rotate and interact with more polar or charged particles, then the kinetic energy will be transformed into heat. This heating can cause adverse effects on body. The brief and strong induced electric field can lead to the dielectric breakdown of cell membranes [4]. According to ‘International Agency for Research on Cancer’, radiofrequency radiation is classified in group 2B as ‘a possible carcinogen’ to humans [5]. The detrimental effects of microwaves on the male reproductive organ were first reported by Prausnitz and Sutsskind [6]. Since 1962, the sources and usage of radiofrequency radiations have increased drastically with a surge in average data consumption per user upto 9.2 GB per month [7].

Some studies suggested the deleterious consequences of RFR exposure on various cell types [[8], [9], [10], [11], [12], [13], [14], [15]] while others have identified insignificant effects [[16], [17], [18], [19], [20]]. Evidences from current literature elucidated the association of RFR emitting devices with the rise in health-related problems such as headaches [[21], [22], [23]], sleep disturbances [[23], [24], [25]], behavioral changes [26], increased risk of cancer [[27], [28], [29], [30]] and possible adverse effects on male fertility [[31], [32], [33]]. Baan et al. (2011) published the IARC Monograph summary and reported that there is no correlation between mobile phone use and increased risk of cancer.

RFR affects living matter in two ways: a) thermal (temperature increase in the range of 1 °C), b) non-thermal (body temperature rise is below 1 °C) [5]. Thermal effects are leading to small temperature variations in exposed tissues changing the conformation of several proteins that are sensitive to temperature variation and, induce the expression of stress response or heat shock proteins [34,35]. There are controversies regarding the non-thermal mechanism of action of RFR. Some authors suggested exposure to RFR induces insignificant biological effects [[36], [37], [38]], while followingother studies, RFR exposure could be linked to significant variation in specific biological parameters [[39], [40], [41], [42]].

‘The International Commission on Non-Ionizing Radiation Protection’ reported that the legal-specific absorption rate (SAR) of cell phones is limited to 2.0 W/Kg, but SAR level differs from one country to another. SAR is the energy absorption per unit mass of body after RF-EMR exposure, and its absorption depends on intensity, polarization, frequency, exposure duration, and position of the electromagnetic device. The nearer the position of EM device, the higher would be the absorption rate [4]. Penetration of RFR into the body tissues depends upon the conductivity and permittivity of the exposed tissue and wavelength of the RF radiation is inversely proportional to the wave frequency. Therefore, penetration of RFR is higher at lower frequencies; approximately 25 % at 900 MHz irradiated human body and about 20 % penetration at a frequency range of 1800 MHz [43]. However, compared to other tissues, the possibility of RFR penetration into the human testis might be more prominent as this organ has lesser tissue protection than other body tissues [44]. Studies reported that testes are sensitive to RFR emitted from Wi-Fi- devices [33]. Abnormality in the testes is observed by significant alteration in the sperm parameters like sperm morphology, motility, viability, sperm count, and sperm percent with severe DNA damage [[45], [46], [47]]. Exposure to cell phone radiations has been found to be associated with a decrease in sperm motility [48] and sperm count [49], suggesting an alteration in male fertility, but these changes are not reported consistently [50]. Another study in humans observed reduction in motility, viability, morphology and concentration of sperm after prolonged exposure to mobile phone radiations [51], showing a probable impact on fertility, while 2.45 GHz RFR emitted from Wi-Fi transmitter mostly affect sperm count, motility and DNA integrity but the effect on sperm morphology and viability were inconclusive [33]. However, pieces of evidences showed mixed results. Some studies found affected sperm motility after RFR exposure, but sperm concentration [52,53] and sperm quality [54] has been found unaffected.

Hence, the biological effects of RFR on the male reproductive parameters remained elusive, indicating the necessity of reviewing the published research related to RFR and male fertility. This review aims to evaluate the possible effects of radiofrequency radiation on the male fertility and suggests some protective measures against radiofrequency radiation exposure based on available literature.