Human volunteers (n=34) were exposed to 900 & 1800 MHz (GSM) on two separate days (one week apart) for 35 minutes at 1 watt (for 1800 MHz) or 2 watts (for 900 MHz) [average SAR at 900 MHz estimated at 1.58 W/kg, average SAR at 1800 MHz estimated at 0.704 W/Kg] based on phantom models. Volunteers were then analyzed for blood pressure, heart rate, breathing rate, core temperature, and cerebral circulation. Blood pressure was taken during controlled breathing , spontaneous breathing , deep breathing, and two Valsalva (holding breath or blowing) maneuvers. No effects were reported due to RF exposure. In additional studies using the same volunteers, exposure to 900 and 1800 MHz (GSM) RF from standard mobile phones set at maximal power output (2 watt peak / 250 mW avg and 1 watt peak / 125 mW avg, respectively) was performed for 35 minutes over the left ear, with an inactive GSM handset placed over the subject's right ear. Testing also included a 35 minute sham exposure and was performed in a double blind manner and in a temperature controlled environment. Subjects were fitted with a thermister temperature probes set in ear plugs and placed within both ear canals. The authors reported statistically significant increases on the order of 1 degree C or more due to mobile phone at the ear, regardless of whether it was transmitting or not. Since the battery was operational in the control mobile phone, the authors suggest the temperature increase due to battery and not a result of RF energy absorption.
AUTHORS' ABSTRACT: Lindholm et al. 2011 (IEEE #5658): The aim of this study was to examine thermal and local blood flow responses in the head area of the preadolescent boys during exposure to radiofrequency (RF) electromagnetic fields produced by a GSM mobile phone. The design was a double-blinded sham-controlled study of 26 boys, aged 14-15 years. The SAR distribution was calculated and modelled in detail. The duration of the sham periods and exposures with GSM 900 phone was 15 min each, and the tests were carried out in a climatic chamber in controlled thermoneutral conditions. The ear canal temperatures were registered from both ear canals, and the skin temperatures at several sites of the head, trunk and extremities. The local cerebral blood flow was monitored by a near-infrared spectroscopy (NIRS), and the autonomic nervous system function by recordings of ECG and continuous blood pressure. During the short-term RF exposure, local cerebral blood flow did not change, the ear canal temperature did not increase significantly and autonomic nervous system was not interfered. The strengths of this study were the age of the population, multifactorial physiological monitoring and strictly controlled thermal environment. The limitations of the study were large inter-individual variation in the physiological responses, and short duration of the exposure. Longer provocation protocols, however, might cause in children distress related confounding physiological responses.