J. Pineal Res. 2001; 31:85–88

Melatonin and 6-OHMS in high-intensitymagnetic fields

Graham C, Cook MR, Gerkovich MM, Sasre A. Melatonin and 6-OHMS in high-intensity magnetic fields. J. Pineal Res. 2001; 31:85–88.© Munksgaard, 2001

Abstract: We determined if all-night exposure to 60 Hz magnetic fieldsat an intensity well within the upper range of occupational exposures(resultant intensity=127.3 microTesla [�T]) resulted in suppression ofmelatonin or its major metabolite 6-hydroxymelatonin-sulfate(6-OHMS) in the first-void morning urine of 24 healthy malevolunteers. Measures collected after continuous and intermittentmagnetic field exposure test conditions were compared to similarmeasures collected after an equivalent no-exposure control condition.Urinary concentrations of melatonin and 6-OHMS did not differ as afunction of type of magnetic field exposure, nor did they differ betweenfield exposure and control conditions. These results demonstrate thatthe nocturnal secretion and metabolism of melatonin are not altered inhumans by field exposure at an intensity over 600 times higher thanthat typically encountered in the home.

Charles Graham, Mary R. Cook,Mary M. Gerkovich andAntonio SastreMidwest Research Institute, Kansas City,Missouri, USA

Key words: cancer – EMF – human –melatonin hypothesis – neuroendocrinesystem – 60 Hz

Address reprint request to Charles Graham,Midwest Research Institute, 425 VolkerBoulevard, Kansas City, Missouri 64110,USAE-mail: cgraham@mriresearch.org

Received July 6, 2000;accepted August 9, 2000.

Introduction

Melatonin is an oncostatic agent capable of func-tioning through a variety of mechanisms [Panzerand Viljoen, 1997; Reiter et al., 1997; Brainard etal., 1999], and manipulation of melatonin levelscan influence the development of various cancersin animals including breast cancer, prostate can-cer, and melanoma [e.g., Blask, 1993]. Exposure topower-frequency electric and magnetic fields(EMF) is hypothesized to increase cancer risk inhumans by altering the normal function of thepineal gland and suppressing the nocturnal in-crease in melatonin synthesis and release [for re-view see Stevens et al., 1997; Portier and Wolfe,1998]. Evidence that EMF exposure suppressesmelatonin in humans, however, has been difficultto obtain under controlled laboratory exposureconditions [for review see Lambrozo et al., 1996;Graham et al., 2000a]. No effects on melatonin, orits major metabolite 6-hydroxymelatonin-sulfate(6-OHMS), have been reported in human expo-sure studies that varied such key magnetic fieldparameters as frequency (50 or 60 Hz), intensity(1–28.3 microTesla [�T]), duration (1–4 consecu-tive nights), polarity (linear or circular polariza-tion), and exposure pattern (continuous orintermittent).

As part of a larger study of the physiologicaleffects of exposure to power-frequency magnetic

fields [Graham et al., 2000b], we obtained first-void morning urine samples to determine if con-centrations of melatonin and 6-OHMS weresuppressed by all-night exposure to 60-Hz mag-netic fields at an intensity over four times higherthan any previously examined in the laboratory(resultant flux density=127.3 �T). This intensityis well within the upper range of occupationalexposures, and it is relevant to recommendationsof the International Commission on Non-IonizingRadiation Protection limiting exposure in the gen-eral population to 100 �T at 50 Hz [ICNIRP,1998].

Materials and methods

A randomized, double-blind, cross-over designwas used, in which each of 24 male volunteersserved as his own control. The men (mean age 21years, range 19–34 years) had regular sleep anddietary habits, did not work evenings or nights,and were not taking medications. The study proto-col was approved by the Midwest Research Insti-tute (MRI) Institutional Review Board for HumanStudies and written informed consent was ob-tained from each volunteer.

The study was performed in the magnetic fieldexposure test facility at MRI. The exposure char-acteristics of this facility have been documented aspart of the U.S. National EMF RAPID research

85Printed in Ireland—all rights reser�ed.

Graham et al.

program [Olden, 1999] and are described inDoynov et al. [1999]. The subjects slept in thefacility on 3 test nights from 23:00 to 07:00 hr.One night was a no-exposure control night, duringwhich the men were exposed only to the ambient60 Hz background magnetic field measured in thelaboratory (�0.2 �T). This intensity is character-istic of residential exposures. On another night,they were exposed continuously to a circularlypolarized, 60 Hz sinusoidal magnetic field gener-ated at an intensity of 127.3 �T. On the thirdnight, they were again exposed to the 127.3 �Tfield, but this time using the intermittent exposureprotocol described by Graham et al. [1996]. Thisconsisted of alternating 1-hr field-on and field-offperiods. During field-off periods, the coils werenot energized. During field-on periods, the fieldcycled on and off at 15-s intervals. Control andfield exposure test sessions were presented in threecounterbalanced orders, so that equal numbers ofsubjects participated in each condition on eachnight.

Subjects did not consume alcohol for 24 hr priorto a test session, and had no caffeine after 17:00 hron the day of a session. On arrival at the labora-tory, the subject emptied his bladder and changedinto sleepwear. At 23:00 hr, the lights in the expo-sure test room were turned off and the double-blind/field-control system was activated. Subjectsremained in bed until morning. First-void morningurine samples (these included all urine voided after23:00 hr) were collected, aliquoted, and frozen at−20°C for later assay.

Melatonin was assayed using the BuhlmannRIA kit (ALPCO Ltd., Windham, NH, USA).The detection limit for this assay is 0.3 pg/mL and,in our hands, the inter- and intra-assay CVs areroutinely below 10% throughout the assay range[Graham et al., 1998; Cook et al., 2000]. 6-OHMSwas assayed using the Stockgrand RIA kit (Guild-ford, Surrey, UK). The inter- and intra-assay CVsfor this assay are also routinely below 10% and thelower limit of quantitation is 3.1 pg/mL. To cor-rect for individual differences in urine volume,urinary creatinine was also assayed using a CobasMira™ chemistry analyzer. 6-OHMS results werenormalized to creatinine concentration and ex-pressed as ng 6-OHMS per mg creatinine. Theassays were performed blind.

Analysis of variance (ANOVA) for mixed de-signs was the primary statistical technique used totest for differences in mean concentrations ofmelatonin and 6-OHMS under control versus in-termittent or continuous magnetic field exposureconditions. The between-subject variable was thethree orders of exposure testing, and the within-

subject variable was the three types of exposure(control, intermittent, and continuous). Probabil-ity values were corrected for lack of sphericityusing the Huynh–Feldt epsilon technique. Statisti-cal significance was set at P�0.05.

Results

ANOVA performed on data from all 24 volun-teers did not reveal any significant field-relateddifferences in the measures derived from first-voidmorning urine as a function of intermittent versuscontinuous magnetic field exposure, or as a func-tion of either exposure condition compared to theno-exposure control condition. This was true formelatonin (F [2,42]=0.40, P=0.66) and for 6-OHMS (F [2,42]=0.79, P=0.46). As expected,morning urinary concentrations of melatonin and6-OHMS varied somewhat within individualsacross the 3 test nights, but no obvious pattern ofsuppression was associated with any particularcondition. For example, 6-OHMS values werelowest in the no-exposure control condition forseven subjects, lowest in the continuous field expo-sure condition for another nine subjects, and low-est in the intermittent exposure condition for theremaining eight subjects. A similar lack of associa-tion was observed for melatonin.

Four individuals were high physiological secre-tors of melatonin relative to the remaining 20subjects (i.e., values, for both melatonin and 6-OHMS, in these subjects were greater than twostandard deviations from the group mean). Whenthese individuals were included in the above analy-ses, the underlying distributions for melatonin and6-OHMS were skewed toward the high end. With-out these individuals, the distributions for mela-tonin and 6-OHMS had acceptable skew andkurtosis. Since data that are not normally dis-tributed can alter statistical outcomes, we decidedto delete the data from these four subjects andperform the ANOVAs again. As shown in Fig. 1,mean concentrations of melatonin and 6-OHMSfor the remaining 20 subjects did not differ acrossmagnetic field exposure and control conditions(melatonin: F [2,34]=0.07, P=0.93; 6-OHMS: F[2,34]=0.82, P=0.45). Thus, whether or not thehigh physiological secretors of melatonin were in-cluded in the analyses, the same results were ob-tained: magnetic field exposure did not altermelatonin or 6-OHMS in first-void morning urine.

Discussion

These results replicate and extend the negativefindings from previous laboratory-based human

86

Magnetic fields and melatonin

Fig. 1. Mean (�S.E.) concentra-tions of melatonin and its majormetabolite (6-OHMS) in first-voidmorning urine from 20 healthy malevolunteers did not differ after all-night exposure to continuous or in-termittent magnetic fields (60 Hz,127.3 �T), compared to no-exposurecontrol conditions (�0.2 �T).

exposure research [for review see Lambrozo et al.,1996; Graham et al., 2000a]. All-night exposure to60-Hz magnetic fields did not suppress levels ofmelatonin or its major metabolite 6-OHMS infirst-void morning urine, even when the volunteerswere exposed at the very high-intensity of 127.3�T. No differences were observed as a result ofintermittent versus continuous magnetic field ex-posure when compared to the no-exposure controlcondition. These results are based on measuresderived from samples of first-void morning urine.Melatonin and 6-OHMS concentrations in suchsamples accurately reflect nocturnal plasma con-centrations of melatonin, both in terms of areaunder the curve and peak values [Lushington etal., 1996; Graham et al., 1998; Cook et al., 2000].The use of creatinine, as a reference parameter for6-OHMS, also provides additional confidence inthe reliability of the results obtained [Klante et al.,1997; Graham et al., 1998] as it adjusts for thedifferent urine volumes produced by individualsubjects. Such a correction is not necessary forurinary melatonin, however, since plasma mela-tonin and kidney tubule melatonin readily equili-brate with one another due to the rapid diffusionof melatonin across lipid membrane structures.

A basic issue of public concern is whether or notexposure to power-frequency EMF results in anyadverse health effects to humans. Exposure tosuch fields, under the controlled laboratory condi-tions created in multiple human exposure studies,has had no demonstrable effect on blood or uri-nary concentrations of melatonin and 6-OHMS.The present study provides additional informationuseful for risk assessment and the alleviation ofunwarranted public concern. Our results demon-

strate that the nocturnal secretion and metabolismof melatonin are not altered in humans by fieldexposure at an intensity over 600 times higherthan that typically encountered in the home. Re-cent field studies of people exposed to EMF athome or at work, however, do report some evi-dence for a small suppression of melatonin [forreview see Portier and Wolfe, 1998]. Thus, thepossibility exists that disturbances of the mela-tonin rhythm may be related to as yet unknownaspects of the more complex fields found in theman-made environment. Further research isneeded to clarify whether the small effects re-ported in the field studies are necessarily related tothe presence of EMF, and to evaluate their rele-vance for public health.

Acknowledgments

Research funding was provided by the National Instituteof Environmental Health Sciences (Grant ES07053), andEPRI (Contract WO8021). We thank Donald W. Riffle,Steven J. Hoffman, Deb Smith, and Brian E. Peterson fortheir valuable help in data collection and analysis.

Literature cited

BLASK, D.E. (1993) Melatonin in oncology. In: Melatonin:Biosynthesis, Physiological Effects, and Clinical Applica-tions, H.S. Yu, R.J. Reiter, eds. CRC Press, Boca Raton, pp.447–475.

BRAINARD, G.C., R. KAVET, L.I. KHEIFETS (1999) The rela-tionship between electromagnetic fields and light exposuresto melatonin and breast cancer risk: A review of the relevantliterature. J. Pineal Res. 26:65–100.

COOK, M.R., C. GRAHAM, R. KAVET, R.G. STEVENS, L.I.KHEIFETS, S. DAVIS (2000) Morning urinary assessment ofnocturnal melatonin secretion in older women. J. Pineal Res.28:41–47.

87

Graham et al.

DOYNOV, P., H.D. COHEN, M.R. COOK, C. GRAHAM (1999)Test facility for human exposure to AC and DC magneticfields. Bioelectromagnetics 20:101–111.

GRAHAM, C., M.R. COOK, D.W. RIFFLE, M.M. GERKOVICH,H.D. COHEN (1996) Nocturnal melatonin levels in humanvolunteers exposed to intermittent 60-Hz magnetic fields.Bioelectromagnetics 17:263–273.

GRAHAM, C., M.R. COOK, R. KAVET, A. SASTRE, D.K.SMITH (1998) Prediction of nocturnal plasma melatoninfrom morning urinary measures. J. Pineal Res. 24:230–238.

GRAHAM, C., M.R. COOK, A. SASTRE, D.W. RIFFLE, M.M.GERKOVICH (2000a) Multi-night exposure to 60-Hz mag-netic fields: Effects on melatonin and its enzymatic metabo-lite. J. Pineal Res. 28:1–8.

GRAHAM, C., A. SASTRE, M.R. COOK, R. KAVET, M.M.

GERKOVICH, D.W. RIFFLE (2000b) Exposure to strong ELFmagnetic fields does not alter cardiac autonomic controlmechanisms. Bioelectromagnetics (in press).

ICNIRP (INTERNATIONAL COMMISSION ON NON-IONIZING

RADIATION PROTECTION) (1998) Guidelines for limitingexposure to time-varying electric, magnetic, and electro-magnetic fields (up to 300 GHz). Health Phys. 74:494–522.

KLANTE, G., T. BRINSCHWITZ, K. SECCI, F. WOLLNIK, S.STEINLECHNER (1997) Creatinine is an appropriate reference

for urinary sulphatoxymelatonin of laboratory animals andhumans. J. Pineal Res. 23:191–197.

LAMBROZO, J., Y. TOUITOU, W. DAB (1996) Exploring theEMF-melatonin connection: A review of the possible effectsof 50/60-Hz electric and magnetic fields on melatonin secre-tion. Int. J. Occup. Environ. Health 2:237–247.

LUSHINGTON, K., D. DAWSON, N. ENCEL, L. LACK (1996)Urinary 6-sulfatoxymelatonin cycle-to-cycle variability.Chronobiol. Int. 13:411–421.

OLDEN, K. (1999) NIEHS Report on Health Effects fromExposure to Power-Line Frequency Electric and MagneticFields. National Institutes of Health, Washington. Publica-tion No. 99-4493.

PANZER, A., M. VILJOEN (1997) The validity of melatonin asan oncostatic agent. J. Pineal Res. 22:184–202.

PORTIER, C.J., M.S. WOLFE (EDS) (1998) Assessment ofHealth Effects from Exposure to Power-Line FrequencyElectric and Magnetic Fields: NIEHS Working Group Re-port. National Institutes of Health, Washington. PublicationNo. 98-3981.

REITER, R.J., L. TANG, J.J. GARCIA, A. MUNOZ-HOYOS

(1997) Pharmacological actions of melatonin in oxygen-radi-cal pathophysiology. Life Sci. 60:2255–2271.

STEVENS, R.G., B.W. WILSON, L.E. ANDERSON (EDS) (1997)The Melatonin Hypothesis: Breast Cancer and the Use ofElectricity. Battelle Press, Columbus, 760 pp.

88