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Effects of the 1900 MHz electromagnetic field emitted from cellular phone on nocturnal melatonin secretion.

of exposure to radio frequency (RF) radiation from personal handy phone system (PHS), with particular reference to cellular telephone handsets. The first consideration is frequency because exposure guidelines vary with frequency. PHS is operated at frequency 1.96 GHz (1906.55611.4 MHz). The whole-body Average Specific Absorption Rates (SAR) was 0.453–0.680 W/kg, power density 2.5 mW/cm, and magnitude 6 mG. Possible mechanisms for biological effects are that an Electromagnetic (EM) wave must deposit enough energy to alter some structure significantly. Recently smaller power-density guidelines were recommended for limiting exposure of the general public to RF radiation. These limits keep humans from being overheated by restricting exposures to levels that were relatively weak (ICNIRP, 1996). The World Health Organization (1993) provided a status report on possible health effects from exposure to low-level radio frequency (RF) and identified gaps in knowledge requiring more research to improve health risk assessments. In animal, subchronic exposure of rats to a 50 Hz rotating magnetic field influences melatonin secretion from pineal gland (Kato et al., 1993). Mann et al. (1998) have also observed changes in several endocrine parameters in humans exposed to EM wave at night. However, there has been very little research on the effects of RF on melatonin secretion, and the few existing studies do not provide clear information (Royal Society of Canada, 1999). The study group consisted of 8 young females, average-age 27 years ranging from 16-36 years old, mean body mass 54.56 1.77 Kg (SE), mean height 161.7565.83 cm (SE), all in the follicular phase of menstrual cycle. The subjects had not used a cellular telephone at least one week before the experiment, and led a well-regulated life for a week prior to participation. The subjects entered the climatic chamber at 10 a.m. In the chamber an ambient temperature and a relative humidity were maintained at 2660.5°C and 6063%, respectively. The light intensity was controlled 1000 Lx from 10:00 h to 18:00 h and 50 Lx from 18:00 h to 01:00 h, then completely dark from 01:00 h to 07:00 h in the next morning. Salivary melatonin was collected at 19:00 h and 2:00 h. For 30 min every hour from 19:00 h to 01:00 h the subjects used a cellular telephone continuously (on one day it emitted electromagnetic fields and on the other day it did not). The receiver was directly attached to the left ear without distance. On exposure (E) day the receiver emitted electromagnetic field, while on sham (S) day there was no emission. The subjects did not know which day was E day, and which day was S. The period (10:00–19:00) till the start of the measurement was treated as a time of adaptation to the experimental chamber. Melatonin concentrations in saliva were measured by enzyme immunoassay using the Bühlmann melatonin enzyme immunoassay (EIA) test kits (Bühlmann Laboratories. AG, Switzerland). Saliva samples were collected with saliva collection tubes for a 10-min period with the subject sitting. The sample was stored at 240°C in a freezer for later analysis. After thawing, the salivary samples were centrifuged at 800 g for 5 min to remove suspended material. The assay was performed according to the manual of melatonin EIA tests kits. The absorbency for each sample was read at 420 nm wavelengths with a micro-plate reader (Model 550 Reader, Bio-rad Laboratories, USA). Fig. 1 compared average salivary melatonin between E and S at 02:00 h. As seen in the figure, the value was significantly lower in E compared with S (p,0.05, by paired t-test). The values at 19:00 h were 31.1615.14 pg/ml without the usage and 29.2815.04 pg/ml with the usage. These were not Effects of the 1900 MHz Electromagnetic Field Emitted from Cellular