A study of the effects of cellular telephone microwave radiation on the auditory system in healthy men.

Abstract

We conducted a study of the effects of mobile cellular telephone microwave radiation on the auditory system in 20 healthy men. After the subjects underwent baseline measurements of transient evoked otoacoustic emission (TEOAE) and auditory brainstem response (ABR), they participated in three sessions of exposure to an electromagnetic field of 900 to 1,800 MHz produced by a cellular phone. Sessions ranged from 15 to 30 minutes in length. TEOAE and ABR were again measured after or during each exposure. Throughout the study, no significant changes in either measurement were noted. We conclude that the use of cellular phones does not alter the auditory system in the short term.

Introduction

The relationship between exposure to electromagnetic fields and human health has been put into sharper focus because of the rapidly expanding use of electromagnetic fields in modem society. Exposure to electromagnetic fields has been linked to different forms of cancer (e.g., brain tumors and leukemia), to neurologic diseases (e.g., Alzheimer's disease), to asthma and allergy, and to two phenomena called electrosupersensitivity and screen dermatitis. (1-5) In this article, we describe our study of the possible short-term effects of cellular-phone-generated electromagnetic waves on the auditory system.

Patients and methods

Our study population was made up of 20 healthy men, aged 20 to 40 years, who were of normal height and weight. These subjects were chosen at random from among the staff at San Martino Hospital in Genoa, Italy. All had normal hearing.

Prior to the start of the study, baseline measurements of transient evoked otoacoustic emission (TEOAE) and auditory brainstem response (ABR) were obtained in all subjects. The study was then conducted in three phases:

Phase 1. Subjects were first exposed to an electromagnetic field of 900 to 1,800 MHz that was produced by a global system for mobile communication (GSM) cellular telephone (Motorola V3690). The phone was placed in the normal position for conversation, with the receiver pressed against each subject's left ear; the phone was supported by a metal stand. The aerial was extended away from the head. Each subject maintained physical contact between the ear and the receiver for 30 minutes continuously. No conversation occurred; subjects were quiet as they were exposed to the silent energy. At the end of this initial exposure period, TEOAE and ABR were again measured.

Phase 2. One hour later, the same ear was then intermittently exposed to the same electromagnetic field for another 30-minute period. During this second phase, subjects carried on 12 telephone conversations of 2 minutes and 30 seconds each. Afterward, TEOAE and ABR were again recorded.

Phase 3. In the third phase 1 hour later, subjects were continuously exposed to the same electromagnetic field for 15 minutes. During this phase, the receiver was held in contact with the left retroauricular mastoid area rather than the ear. TEOAE was recorded during the exposure at 0, 10, and 15 minutes.

Results

All baseline TEOAE and ABR measurements were normal. Following exposure during phase 1, no significant changes were observed in TEOAE or ABR. Likewise, no significant changes were observed after phase 2 and during phase 3.

After each phase, all subjects reported a warm sensation in the area of contact with the receiver and in the area of the antenna.

Discussion

The degree of adverse biologic effects of cellular phone microwave radiation (e.g., radiofrequency sickness, electroencephalographic and blood pressure changes, and cancer risks) depends on many factors, including the duration of exposure to the radiation and the individual characteristics of a given patient's central nervous system and immune status . (2,4,6,7) Cellular phone microwave radiation can induce reversible, nonspecific adaptive responses when the duration of exposure is short and the affected organism is very radiosensitive. The results of some studies of the biologic effects of low-intensity modulated microwave radiation, including that generated by cellular phones, have led investigators to conclude that such radiation does not exert any lasting pathologic effects on the body. (6,7)

Other studies have shown that ultrahigh-frequency radiation induces significant changes in local temperature and in the physiologic parameters of the central nervous and cardiovascular systems. (8-12) Among these changes are an increase in blood pressure values, locoregional vasodilation, and transient inflammation brought about by an increase in the permeability of the erythrocyte membrane. The mechanism of the increase in the permeability of the erythrocyte membrane is not well understood. It might be the result of a hemolytic effect linked to the destabilization of divalent calcium-protein bridges. Such effects occur only after tissue has been exposed to microwave fields for at least 30 consecutive minutes. (8,13)

The heat sensation reported by our subjects was caused by the activation of inflammatory mechanisms. The release of inflammatory substances (e.g., histamine) from macrophages in the skin results in a local erythema, edema, and sensations of itching and pain, and the release of somatostatin from the dendritic ceils may give rise to subjective sensations of ongoing inflammation. (14,15)

In the literature, the use of cellular phones has been associated with very few effects on the auditory system. One of these effects is an auditory sensation that occurs as a result of the thermoelastic expansion of cerebral tissues, which causes a slight but sudden increase in temperature secondary to the absorption of the incident energy. These effects are therefore limited to those high frequencies that penetrate the skull and are significantly absorbed by the cerebral tissue. The expansion causes an acoustic pressure wave that is transmitted through the cranial bones to the cochlea, where the acoustic receptors react as they would to a common auditory stimulus. (16)

Kellenyi et al studied trends in ABR before and after exposure to radiofrequencies emitted by GSM cellular telephones. (17 They discovered a 0.207-msec increase in the latency of the V wave on the side of the exposed ear. This increase corresponded with a 20-dB hearing loss from 2,000 to 10,000 Hz. On the side of the unexposed ear, they recorded a 0.029-msec increase in latency, which was probably attributable to the contralateral effects of cross-interference. Moreover, physiologic alterations in the auditory system of rats have been observed after exposure to low levels of microwave electromagnetic fields. (1,18)

In our study, we observed no alterations involving the auditory system after short-term continuous or intermittent exposure to electromagnetic waves emitted by a cellular phone. It is possible that the absence of change was related to the duration of the exposure (30 min maximum), which was not long enough to result in a temperature increase in tissue. It is noteworthy that no detectable changes were seen even during phase 2, when subjects participated in numerous short telephone calls and were exposed to the increased electromagnetic field that was generated at the beginning of each call.

Concerns have been expressed that the use of cellular phones might cause brain tumors. Certainly, if such a risk does exist, the matter would be of considerable public health importance, given the wide popularity of these devices. However, published data do not support the hypothesis that the use of a cellular phone causes brain tumors over the short term. Data on long-term (>1 yr) risks among heavy cellular phone users are not yet available. (19-21) Other studies have shown that radiofrequency fields--particularly those generated by cellular phones--are not genotoxic. Also, they do not seem to be teratogenic, and they do not appear to induce cancer. (22-25)

We conclude that the use of cellular phones does not alter the auditory system in the short term. We intend to continue monitoring these subjects in order to document the possible appearance of any long-term hearing alterations.

References

(1.) Gangi S, Johansson O. A theoretical model based upon mast cells and histamine to explain the recently proclaimed sensitivity to electric and/or magnetic fields in humans. Med Hypotheses 2000;54: 663-71.

(2.) Hermann DM, Hossmann KA. Neurological effects of microwave exposure related to mobile communication. J Neurol Sci 1997; 152: 1-14.

(3.) Hyland GJ. Physics and biology of mobile telephony. Lancet 2000;356:1833-6.

(4.) Repacholi MH, Basten A, Gebski V, et al. Lymphomas in E mu-Pim1 transgenic mice exposed to pulsed 900 MHZ electromagnetic fields. Radiat Res 1997;147:631-40.

(5.) Lyle DB, Schechter P, Adey WR, Lundak RL. Suppression of T-lymphocyte cytotoxicity following exposure to sinusoidally amplitude-modulated fields. Bioelectromagnetics 1983;4:281-92.

(6.) Galeev AL. [Effects of the microwave radiation from the cellular phones on humans and animals]. Ross Fiziol Zh Im I M Sechenova 1998;84:1293-1302.

(7.) Galeev AL. The effects of microwave radiation from mobile telephones on humans and animals. Neurosci Behav Physiol 2000;30:187-94.

(8.) Cleary SF, Liu LM, Garber F. Erythrocyte hemolysis by radiofrequency fields. Bioelectromagnetics 1985;6:313-22.

(9.) Galvin MJ, McRee DI. Influence of acute microwave radiation on cardiac function in normal and myocardial ischemic cats. J Appl Physiol 1981;50:931-5.

(10.) Santini R, Seigne M, Bonhomme-Faivre L. [Danger of cellular telephones and their relay stations]. Pathol Biol (Paris) 2000;48: 525-8.

(11.) Bartunek P. [Health risks of mobile phones]. Cas Lek Cesk 2001;140:439-42.

(12.) Khudnitskii SS, Moshkarev EA, Fomenko TV. [On the evaluation of the influence of cellular phones on their users]. Med Tr Prom Ekol 1999;9:20-4.

(13.) Liburdy RP, Rowe AW, Vanek PF Jr. Microwaves and the cell membrane. IV. Protein shedding in the human erythrocyte: Quantitative analysis by high-performance liquid chromatography. Radiat Res 1988;114:500-14.

(14.) Liburdy RP, Penn A. Microwave bioeffects in the erythrocyte are temperature and pO2 dependent: Cation permeability and protein shedding occur at the membrane phase transition. Bioelectromagnetics 1984;5:283-91.

(15.) Elgart ML. Cell phone chondrodermatitis [letter]. Arch Dermatol 2000;136:1568.

(16.) Marino C, Cristalli G, Galloni P, et al. Effects of microwaves (900 MHz) on the cochlear receptor: Exposure systems and preliminary results. Radiat Environ Biophys 2000;39:131-6.

(17.) Kellenyi L, Thuroczy G, Faludy B, Lenard L. Effects of mobile GSM radiotelephone exposure on the auditory brainstem response (ABR). Neurobiology (Bp) 1999;7:79-81.

(18.) Liburdy RP, Vanek PF Jr. Microwaves and the cell membrane. II. Temperature, plasma, and oxygen mediate microwave-induced membrane permeability in the erythrocyte. Radiat Res 1985; 102:190-205.

(19.) Inskip PD, Tarone RE, Hatch EE, et al. Cellular-telephone use and brain tumors. N Engl J Med 2001;344:79-86.

(20.) Muscat JE, Malkin MG, Thompson S, et al. Handheld cellular telephone use and risk of brain cancer. JAMA 2000;284:3001-7.

(21.) Moulder JE, Foster KR, Erdreich LS, McNamee JP. Mobile phones, mobile phone base stations and cancer: A review. Int J Radiat Biol 2005;81:189-203.

(22.) Vijayalaxmi, Bisht KS, Pickard WF, et al. Chromosome damage and micronucleus formation in human blood lymphocytes exposed in vitro to radiofrequency radiation at a cellular telephone frequency (847.74 MHz, CDMA). Radiat Res 2001;156:430-2.

(23.) Vijayalaxmi, Leal BZ, Meltz ML, et al. Cytogenetic studies in human blood lymphocytes exposed in vitro to radiofrequency radiation at a cellular telephone frequency (835.62 MHz, FDMA). Radiat Res 2001;155:113-21.

(24.) Verschaeve L, Maes A. Genetic, carcinogenic and teratogenic effects of radiofrequency fields. Mutat Res 1998;410:141-65.

(25.) Jauchem JR. Health effects of microwave exposures: A review of the recent (1995-1998) literature. J Microw Power Electromagn Energy 1998;33:263-74.

Renzo Mora, MD; Barbara Crippa, MD; Francesco Mora, MD; Massimo Dellepiane, MD

From the ENT Department, San Martino Hospital, University of Genoa, Italy.

Reprint requests: Renzo Mora, MD, Via dei Mille 11/9, 16147 Genoa, Italy. Phone: [phone]; fax: [phone]; e-mail: [e-mail]