Specific Absorption Rate (SAR) measures the rate at which RF energy is absorbed by body tissue, expressed in watts per kilogram (W/kg). SAR is used to rate cell phones and other devices held against the body. The FCC limit for cell phones is 1.6 W/kg averaged over 1 gram of tissue.
Based on Building Biology Institute guidelines (W/kg (watts per kilogram)):
See where common exposures fall on the scale:
Showing 898 studies with measured sar (specific absorption rate) exposure
Ammari M et al. · 2010
French researchers exposed rats to cell phone radiation for 8 weeks and found increased brain inflammation markers that lasted at least 10 days after exposure ended. This suggests chronic mobile phone use may trigger inflammatory brain responses similar to those seen in neurodegenerative diseases.
Ammari M et al. · 2008
Researchers investigated the effects of sub-chronic and chronic head-only exposure to 900 MHz GSM signals on spatial memory in male rats. Rats were exposed for 45 minutes per day at a SAR of 1.5 W Kg(-1), or 15 minutes per day at a SAR of 6 W Kg(-1), for either 8 or 24 weeks, and then tested in a radial-arm maze. Spatial memory was unaffected in the exposed rats, while scopolamine-treated positive control rats showed a deficit in the spatial memory task.
Ammari M et al. · 2008
French researchers exposed rats to cell phone radiation (900 MHz) for 24 weeks and found that high-level exposure caused persistent brain inflammation. The study measured GFAP, a protein that increases when brain support cells called astrocytes become activated in response to injury or stress. This suggests that chronic cell phone radiation exposure may trigger ongoing inflammatory responses in brain tissue.
Ammari M, Lecomte A, Sakly M, Abdelmelek H, de-Seze R. · 2008
French researchers exposed rats to cell phone radiation and measured brain enzyme activity. High-intensity exposure (6 W/kg) for 15 minutes daily reduced brain activity in memory and decision-making regions after one week. Lower exposures showed no effects, suggesting intensity matters for brain function.
Brillaud E, Piotrowski A, de Seze R. · 2007
French researchers exposed rats to cell phone radiation (900MHz GSM signal) for just 15 minutes and then examined their brains over the following 10 days. They found significant increases in glial cell activity (brain cells that support and protect neurons) in multiple brain regions, peaking 2-3 days after exposure. This glial response indicates the brain was reacting to the radiation exposure as if responding to injury or stress.
Brillaud E, Piotrowski A, de Seze R · 2007
Researchers measured GFAP expression in rat brains 2, 3, 6, and 10 days after a single 15-minute 900 MHz GSM exposure at a brain averaged SAR of 6 W/kg. A statistically significant increase in GFAP stained surface area was observed 2 days after exposure in the frontal cortex and the caudate putamen. A smaller statistically significant increase was noted 3 days after exposure in those same areas and in the cerebellum cortex. The researchers concluded this was a temporary effect, probably due to a hypertrophy of glial cells, and noted that whether the effect could be harmful remains to be studied.
Mausset-Bonnefont AL et al. · 2004
Researchers used a head-only exposure device to expose rats to 900-MHz pulsed microwaves at 6 W/kg for 15 minutes. The exposure induced a strong glial reaction in the brain, particularly in the striatum. Significant immediate effects were observed on the Kd and Bmax values of NMDA and GABA(A) receptors and on dopamine transporters, along with a decrease in NMDA receptors at the postsynaptic membrane. General locomotor behavior was not significantly altered in the short term.
Adair ER, Cobb BL, Mylacraine KS, Kelleher SA, · 1999
Researchers measured thermoregulatory responses in two groups of seven adult volunteers exposed for 45 minutes to whole-body radio-frequency fields at either 450 or 2450 MHz. At each frequency, two power densities were tested at each of three ambient temperatures (24, 28, and 31 degrees C), along with no-RF control conditions. No change in metabolic heat production occurred under any exposure conditions at either frequency. At both frequencies, normalized peak SARs in excess of ANSI/IEEE C95.1 guidelines were easily counteracted by normal thermophysiological mechanisms.
Behari J, Kunjilwar KK, and Pyne S · 1998
Researchers studied the effect of low-level amplitude-modulated radiofrequency radiation on Na+–K+-ATPase activity in the brains of developing male Wistar rats aged 23 days. Rats were exposed to carrier wave frequencies of 147 MHz and its sub-harmonic frequencies 73.5 and 36.75 MHz, amplitude modulated at 16 and 76 Hz, for 30–35 days at 3 hours per day. Na+–K+-ATPase activity increased by around 19–20% in rats exposed with amplitude modulation at 16 Hz, and by around 15–16% in rats exposed with amplitude modulation at 76 Hz, compared to controls. The researchers concluded that the effect on Na+–K+-ATPase activity was insensitive to the carrier wave frequencies under investigation.
Hao Y, Yang X, Chen C, Yuan-Wang, Wang X, Li M, Yu Z · 2010
Researchers exposed murine N9 microglial cells to 2.45 GHz electromagnetic fields and examined several molecular markers of cell activation. After exposure, a significant increase of STAT3 DNA-binding ability was noted, and EMF rapidly induced phosphorylation of STAT3 and activated JAK1 and JAK2. Transcription levels of the inflammation-associated genes iNOS and TNF-alpha also increased after EMF exposure. When a JAK inhibitor called P6 was applied, it reduced induction of iNOS and TNF-alpha, nuclear factor binding activity, and activation of STAT3 in EMF-stimulated microglia.
Maes A, Collier M, Verschaeve L · 2000
Researchers exposed human lymphocytes to 455.7 MHz microwaves from a car phone at a specific absorption rate of approximately 6.5 W/kg. No statistically significant difference was found between microwave-exposed and unexposed control samples for chromosome aberration or sister chromatid exchange frequency. When microwave exposure was followed by MMC treatment, some differences appeared between combined and MMC-only treatments, but results were inconsistent. Combined exposure with X-rays showed no indication of synergistic action between RF fields and X-rays. The authors concluded that the data do not support the hypothesis that RF fields act synergistically with chemical or physical mutagens.
Harvey C, French PW · 2000
Researchers exposed a human mast cell line, HMC-1, to continuous wave microwave radiation at 864.3 MHz at an average specific absorption rate of 7 W/kg. Cells were given three exposures each of 20-min duration daily for 7 days. Expression of three genes out of 588 screened was affected, including the proto-oncogene c-kit, the transcription factor Nucleoside diphosphate kinase B, and the apoptosis-associated gene DAD-1. No significant effect on morphology or on F-actin distribution was detected.
Harvey C, French PW. · 2000
Researchers exposed human immune cells (mast cells) to microwave radiation at 864.3 MHz for 20 minutes daily over a week, using power levels that kept the cells cooler than body temperature. They found that this non-thermal exposure altered the activity of protein kinase C (a key cellular signaling molecule) and changed the expression of three genes, including one linked to cancer development and another associated with cell death.
Natarajan M, Vijayalaxmi , Szilagyi M, Roldan FN, Meltz ML · 2002
Kim TH et al. · 2008
Researchers used a carousel-type chamber to expose the heads of C57BL mice to 849 MHz or 1763 MHz RF radiation. Mice were irradiated intermittently at 7.8 W/kg for up to 12 months. Brain tissues collected at 6 and 12 months showed no differences in histology, cell proliferation, NeuN and GFAP expression in hippocampus and cerebellum, or cell death between exposure and control groups. Body weights did not differ among sham, 849 MHz, and 1763 MHz groups during the study.
Kim TH et al. · 2008
Researchers exposed mice to cell phone radiation at 849 MHz and 1763 MHz frequencies for up to 12 months, using radiation levels about 4 times higher than current safety limits. They found no changes in brain cell death, cell growth, or tissue damage compared to unexposed mice. This suggests that chronic exposure to these specific frequencies at high levels may not cause detectable brain tissue changes in mice.
Sauter C et al. · 2011
Researchers tested 30 healthy young men exposed to GSM 900, WCDMA, and sham signals over nine study days. After correction for multiple testing, only time-of-day effects remained significant in two tests, resulting in faster reactions in the afternoon trials. Univariate comparisons revealed significant changes for GSM 900 only in the vigilance test. WCDMA exposure altered one parameter in vigilance and one in divided attention, while selective attention and the n-back task were not affected by either exposure.
Ruigrok HJ et al. · 2018
Researchers monitored TRPV1 activation in real time on live cells using a bioluminescence resonance energy transfer technique. Transiently-transfected HEK293T cells were exposed to 1800 MHz radiofrequency signals including CW, GSM, UMTS, LTE, Wi-Fi and WiMAX at specific absorption rates between 8 and 32 W/kg. TRPV1 channels were activated by the heat produced by radiofrequency exposure, but no activation occurred without temperature elevation. Radiofrequency exposure did not alter the maximal efficacy of capsaicin to activate TRPV1 at fixed temperature.
Pashovkina MS, Akoev IG · 2000
Researchers studied the activity of alkaline phosphatase during exposure to pulse-modulated microwave radiation. The carrier frequency was 2375 MHz with modulation pulse rates of 10-390 Hz, on-off time ratio 2, and specific absorption rates of 8 and 0.8 microW/cm2. At a modulation frequency of 70 Hz, alkaline phosphatase activity increased 1.8-2.0 times. Exposure times were 1 and 3 minutes under continuous temperature control.
Pakhomov AG, Dubovick BV, Degtyariov IG, Pronkevich AN · 1995
Researchers studied the combined effects of microwave radiation and drugs on an isolated frog auricle preparation. Exposure to pulse-modulated 915 MHz microwaves for up to 40 minutes had no effect on the rate or amplitude of spontaneous auricle twitches unless the absorbed power caused heating. Caffeine (1 mM) strongly increased the average heart power, and this effect was significantly augmented by about 15% under burst-type pulsed microwaves with an average SAR of 8-10 W/kg, while heating was only approximately 0.1°C.
David G. Cogan et al. · 1958
Mickley GA, Cobb BL · 1998
Tolerant rats showed significantly lower hyperthermia on Day 2 and explored the novel object similarly to sham-exposed rats, whereas non-tolerant rats did not show a preference for the new object. Naltrexone (10 mg/kg) administered just before exposure blocked the hyperthermia-induced discrimination deficit in non-tolerant rats, making their exploration pattern resemble that of tolerant and sham-exposed animals.
Unknown authors
Researchers exposed paired frog sciatic nerves treated with ouabain to microwaves at a specific absorption rate of 10 W/kg while stimulating at 50 pulse pairs per second. At 50 ppps, ouabain reduced the half-decay time from about two hours to under 30 minutes, and microwave exposure caused no significant further shortening. At a lower stimulation rate of 5 ppps, half-decay times returned to near two hours and again showed no significant difference between exposed and unexposed nerves. The authors suggested that microwave effects on nerve vitality are associated with decay of ionic gradients normally maintained by active transport.
Akbarnejad Z et al. · 2017
Researchers exposed rats with Alzheimer's-like brain damage to 50 Hz electromagnetic fields (the same frequency as power lines) for 14 days and tested their memory using a water maze. The electromagnetic field exposure significantly improved the rats' learning and memory abilities, even reversing some of the cognitive damage. This suggests that certain electromagnetic frequencies might have therapeutic potential for neurodegenerative conditions.
Sannino A et al. · 2009
Lymphocytes were collected at 72 hours to measure micronuclei frequency in cytokinesis-blocked binucleated cells. Four donors exhibited a significant reduction in micronuclei after RF pre-exposure, indicating an adaptive response. One donor showed no significant difference in micronuclei between pre-exposed and unexposed cells, indicating a non-responder. The data indicated heterogeneity in the induction of an adaptive response between individuals exposed to RF radiation.