Bioelectromagnetics 27:667 ^ 673 (2006) No Association Between Occupational Exposure to ELF Magnetic Field and Urinary 6 -Sulfatoximelatonin in Workers Fabriziomaria Gobba,* Giulia Bravo, Meri Scaringi, and Luigi Roccatto Chair of Occupational Medicine, Department of Public Health Sciences, University of Modena and Reggio Emilia, Modena, Italy A suppression in melatonin secretion is one of the mechanisms proposed to explain the possible adverse effects of extremely low frequency magnetic fields (ELF-MF), but the results of research are inconclusive. This study investigated the effect of occupational ELF-MF exposure on 6-sulfatoximelatonin (6-OHMS). Exposure was monitored for three complete work shifts in 59 workers using personal exposure meters. Environmental exposure was also evaluated. Urinary 6-OHMS in morning samples, an indicator of night-time melatonin production, was measured. Urine was collected twice on Friday and the following Monday. Workers were classified according to ELF exposure as low exposed (0.2 mT) or higher exposed (>0.2 mT): 6-OHMS did not differ between groups (P >.05) in either Friday or Monday urine samples. In addition, 6-OHMS was not related to exposure under multivariate analysis. The ratio between 6-OHMS in Monday versus Friday samples was also calculated to test the hypothesis of a possible variation in pineal function after 2 days, interruption of occupational ELF-MF exposure: again no exposure-related difference was observed. Our results do not support the hypothesis that occupational exposure to ELF-MF significantly influences melatonin secretion. Bioelectromagnetics 27:667– 673, 2006. ß 2006 Wiley-Liss, Inc. Key words: ELF magnetic fields; personal dosimetry; humans; melatonin secretion INTRODUCTION The potential health risk of exposure to extremely low frequency magnetic fields (ELF-MF) has received considerable attention in recent years, mainly due to the ubiquitous presence of electricity and electrical appli- ances in the home and workplace and some findings suggesting the occurrence of adverse health effects [NRPB, 2001; IARC, 2002]. Intensive research into possible carcinogenic effects was stimulated by the epidemiological association between residential expo- sure and childhood leukemia reported more than 25 years ago by Wertheimer and Leeper [1979]. According to an overall evaluation of results, ELF- MF is currently considered ‘‘possible carcinogens’’ in childhood, whereas data in adults are deemed insuffi- cient [ICNIRP, 2001; NRPB, 2001; IARC, 2002]. Other effects possibly related to ELF-MF exposure in adults include an increased risk of depression and suicide [ICNIRP, 2001; NRPB, 2001], and sleep disorders [Akerstedt et al., 1998; Graham and Cook, 1999; Graham et al., 2000; Arendt, 2003]. An effect on immune function was also reported [Boscolo et al., 2000; Gobba et al., 2002]. A single mechanism that may explain all these effects is a suppression in melatonin secretion, the so-called ‘‘melatonin hypothesis’’ [Stevens and Davis, 1996]. There is now compelling evidence that this hormone may reduce the incidence and certainly the growth of tumors [Panzer and Viljoen, 1997; Reiter, 2004] and enhance the immune response [Maestroni, 1993]. Furthermore, reduced melatonin secretion may be related to sleep disturbances and depression [Thompson et al., 1988; Arendt, 2003]. Several studies have addressed the effect of ELF-MF on melatonin secretion. Some in-vivo studies reported a suppression in small animals [e.g., Reiter, 1994; Lambrozo et al., ß 2006 Wiley-Liss, Inc. —————— Grant sponsor: Italian Ministero del Lavoro e della Previdenza Sociale; Grant number: 906. *Correspondence to: Fabriziomaria Gobba, MD, Prof., Chair of Occupational Medicine, Department of Public Health Sciences, University of Modena and Reggio Emilia, Via Campi 287, 41100 (MO), Italy. E-mail: f.gobba@unimore.it Received for review 9 August 2005; Final revision received 6 March 2006 DOI 10.1002/bem.20254 Published online 20 September 2006 in Wiley InterScience (www.interscience.wiley.com).