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
Moretti D et al. · 2013
French researchers exposed lab-grown brain cell networks to cell phone radiation (GSM-1800) for 3 minutes and measured their electrical activity in real time. They found that the radiation caused a 30% decrease in the brain cells' firing rate and bursting patterns - essentially making the neurons less active. The effect was reversible, meaning the cells returned to normal activity after exposure ended.
Moretti D et al. · 2013
Researchers developed a dedicated experimental setup for the simultaneous exposure of neuronal networks and monitoring of electrical activity. In this pilot study on 16 cultures, there was a 30% reversible decrease in firing rate and bursting rate during a 3-minute exposure. The researchers noted that additional experiments are needed to further characterize this effect.
Moisescu MG, Leveque P, Verjus MA, Kovacs E, Mir LM. · 2009
The exposure increased Lucifer Yellow uptake, and this increase was not due to heating. Chlorpromazine and ethanol blocked the increase while Filipin did not, indicating involvement of clathrin-coated vesicles.
Hook GJ et al. · 2004
Researchers exposed Molt-4 T lymphoblastoid cells to CDMA, FDMA, iDEN, and TDMA modulated RF radiation for up to 24 hours. DNA damage was measured with the single-cell gel electrophoresis assay and apoptosis with the annexin V affinity assay. No statistically significant difference in DNA damage or apoptosis was observed between sham and exposed cells for any frequency, modulation, or exposure time.
Bisht KS, Moros EG, Straube WL, Baty JD, Roti Roti JL · 2002
Researchers exposed C3H 10T½ cells to 835.62 MHz FDMA or 847.74 MHz CDMA modulated radiofrequency radiation to determine whether it caused micronuclei to form. Cells were exposed at power levels of 3.2 or 4.8 W/kg for CDMA and 3.2 or 5.1 W/kg for FDMA, for durations of 3, 8, 16, or 24 hours. In three repeat experiments, no exposure condition produced a significant increase in micronuclei compared to sham-exposed cells.
Li L et al. · 2001
Researchers exposed murine C3H 10T(1/2) fibroblasts to radiofrequency fields at specific absorption rates of 3.2 to 5.1 W/kg. Cell cultures were exposed to 847.74 MHz CDMA and 835.62 MHz FDMA modulated radiations in radial transmission line irradiators with temperature regulated to 37.0 ± 0.3 °C. Using the alkaline comet assay, they found no statistically significant differences in comet moment or comet length between sham-exposed and exposed cells after 2, 4, or 24 hours of exposure, for both exponentially growing and plateau-phase cells. A 4-hour incubation after a 2-hour exposure also resulted in no significant changes in comet moment or comet length. The authors concluded that exposure at 37°C up to 5.1 W/kg did not induce measurable DNA damage.
Saygin M, Caliskan S, Karahan N, Koyu A, Gumral N, Uguz A · 2011
Researchers used twelve-week-old male Wistar Albino rats divided into cage control, sham control, and 2.45 GHz EMR groups, with the exposure group receiving 3.21 W/kg for 60 minutes daily over 28 days. The exposed rats showed a significant reduction in Leydig cell numbers compared to cage controls. Spermatogenesis scores differed significantly between groups, and Bax gene and Caspase-8 enzyme levels showed significant changes.
Zeng Q, Chen G, Weng Y, Wang L, Chiang H, Lu D, Xu Z. · 2006
Researchers investigated gene and protein responses to GSM 1800 MHz RF EMF in human breast cancer MCF-7 cells using genomic and proteomic approaches. GeneChip analysis identified a handful of changed genes after exposure at SAR up to 3.5 W/kg for 24 hours, but these changes were not confirmed by RT-PCR. Proteome analysis found a few different proteins differentially expressed under continuous or intermittent exposure at SAR 3.5 W/kg for 24 hours or less, but the authors suggest these effects might have occurred by chance.
Zeng QL, Weng Y, Chen GD, Lu DQ, Chiang H, Xu ZP · 2006
Researchers exposed MCF-7 human breast cancer cells to GSM 1800 MHz RF EMF at 3.5 W/kg SAR for various durations and modes. They used 2-dimensional electrophoresis and PDQuest software to analyze protein expression. No differential proteins were found after 6 hours of continuous exposure. Eighteen differential proteins were detected after 3-hour intermittent exposure and seven after 12-hour continuous exposure. The analysis suggested that the differentially expressed proteins should be related to biosynthesization, signal transduction, and DNA damage and repair.
Li R et al. · 2018
Mouse spermatocyte-derived cells (GC-2) were exposed to radiofrequency electromagnetic fields at 4 W/kg for 24 hours. The exposure induced both autophagy and DNA damage in GC-2 cells through the generation of reactive oxygen species. When autophagy was blocked by knocking down AMPKα, DNA damage increased, while overexpressing AMPKα promoted autophagy and reduced DNA damage.
Kim JH, Kim HJ, Yu DH, Kweon HS, Huh YH, Kim HR. · 2017
Researchers studied the effects of RF-EMF exposure on synaptic vesicles in the cortical neurons of mice. C57 BL/6 mice were exposed to 835 MHz RF-EMF at 4.0 W/kg SAR for 5 hours daily. The density of synaptic vesicles was significantly decreased in the presynaptic boutons of cortical neurons after exposure. The expression of synapsins I/II genes and proteins was also significantly decreased in exposed mice.
Kim JH, Yu DH, Huh YH, Lee EH, Kim HG, Kim HR. · 2017
Researchers exposed C57BL/6 mice to 835 MHz RF-EMF at a specific absorption rate of 4.0 W/kg for 5 hours per day during 12 weeks. The study found that RF-EMF exposure led to myelin sheath damage and that mice displayed hyperactivity-like behavior. Autophagy-related proteins including LC3B-II and Beclin1 were increased in neuronal cell bodies, and the researchers suggest autophagy may act as a protective pathway during radiofrequency exposure.
Kim JH et al. · 2017
Researchers exposed C57BL/6 mice to 835 MHz RF-EMF at an SAR of 4.0 W/kg for 12 weeks, then analyzed the hippocampus and brain stem. Several autophagic genes were significantly upregulated only in the hippocampus and not in the brain stem. Transmission electron microscopy revealed an increase in the number of autophagosomes and autolysosomes in the hippocampal neurons of exposed mice.
Su L, Wei X, Xu Z, Chen G · 2017
Researchers exposed neurogenic A172, U251, and SH-SY5Y cells to 1800 MHz RF-EMF at 4.0 W/kg intermittently for 1, 6, or 24 hours. DNA damage was measured by quantifying γH2AX foci, an early marker of DNA double-strand breaks. Cell cycle progression, proliferation, and viability were assessed using flow cytometry, hemocytometer, and cell counting kit-8 assay. Exposure did not significantly induce γH2AX foci formation or cause abnormal cell cycle progression, proliferation, or viability. Prolonged incubation up to 48 hours after exposure also did not significantly affect cellular behavior.
Sun C, Wei X, Fei Y, Su L, Zhao X, Chen G, Xu Z. · 2016
Researchers compared the effects of 1,800 MHz RF-EMF exposure on genomic DNA in mouse embryonic fibroblasts with proficient (Atm+/+) or deficient (Atm−/−) ATM. In Atm+/+ cells, exposure for 1 hour at an average special absorption rate of 4.0 W/kg induced significant DNA single-strand breaks and activated the SSB repair mechanism. That repair effect reduced DNA damage to less than background levels after 36 hours of exposure. In Atm−/− cells, the same RF-EMF exposure for 12 hours induced both SSBs and double-strand breaks and activated the two repair processes, also reducing damage below the control level after prolonged exposure. The researchers described this as the first reported hormesis-like effect of an RF-EMF.
Sun C, Wei X, Fei Y, Su L, Zhao X, Chen G, Xu Z · 2016
Researchers exposed mouse embryonic cells to 1,800 MHz radiofrequency radiation (similar to cell phone signals) at high power levels for 1-12 hours and found it initially caused DNA breaks. However, after prolonged exposure, the cells' DNA repair systems became so active that DNA damage dropped below normal background levels - a phenomenon called hormesis where low doses of a harmful substance trigger beneficial protective responses.
Wang C et al. · 2015
Court-Kowalski S et al. · 2015
Researchers exposed mice to 900 MHz RF fields at 4 W/kg for 104 weeks, five days per week. Control mice were sham-exposed or freely moving in cages. No change in astrocytic GFAP immunostaining was found in exposed mice compared to controls.
Kim HS et al. · 2013
Male Sprague-Dawley rats were divided into cage-control, sham-exposed, and RFID-exposed groups and exposed to 915 MHz RFID for 8 h daily, 5 days per week, for 2 or 16 weeks. The whole-body average specific absorption rate was 4 W/kg. FDG-PET images were obtained the day after RFID exposure using micro-PET with a FDG tracer, and the relative cerebral glucose metabolic rate was unchanged in the frontal, temporal and parietal cortexes of exposed rats compared with cage-control and sham-exposed groups.
Poulletier de Gannes F et al. · 2013
Researchers exposed male and female Wistar rats to a 2450 MHz Wi-Fi signal for 1 hour per day, 6 days per week. Exposure lasted 3 weeks for males and 2 weeks for females before mating, then continued for 3 more weeks during gestation. No deleterious effects on reproductive organs or fertility were observed, and no macroscopic abnormalities were found in fetuses even at 4 W/kg.
Kim HS et al. · 2013
Researchers exposed rats to 915 MHz RFID radiation for up to 16 weeks at high intensity levels (4 W/kg SAR) and measured brain glucose metabolism using advanced PET scanning. They found no changes in how the brain processed glucose in any region examined, suggesting this type of radiofrequency exposure didn't alter basic brain energy function. This matters because brain glucose metabolism is a fundamental indicator of neural activity and health.
Laudisi F et al. · 2012
Researchers exposed pregnant mice to WiFi signals at 2450 MHz with a specific absorption rate of 4 W/kg for two hours daily during gestation. Thymocyte count, phenotype, and proliferation were unchanged in exposed offspring. These null effects were consistent in both sexes at 5 and 26 weeks of age.
Hong MN et al. · 2012
Researchers exposed human MCF10A mammary epithelial cells to single frequencies of 837 MHz or 1950 MHz, or both frequencies together, at a SAR of 4 W/kg for 2 hours while maintaining isothermal temperature. They measured intracellular ROS, SOD enzyme activity, and GSH/GSSG ratio and found no statistically significant alterations from either single or multiple RF radiation exposures. Ionizing radiation used as a positive control showed evident changes in all measured endpoints. The results indicate that single or multiple RF radiation exposure did not elicit oxidative stress in MCF10A cells under these conditions.
Sambucci M et al. · 2010
Researchers exposed pregnant mice to WiFi signals for 2 hours daily over 14 consecutive days starting 5 days after mating. No effects were found on mating success, number of newborns per mother, or body weight at birth. Offspring showed no differences in spleen cell number, B-cell frequency, or antibody serum levels. B cells from all groups produced comparable IgM and IgG and proliferated similarly when challenged with LPS in vitro. These findings were consistent in both female and male offspring at juvenile and adult ages.
Finnie JW, Cai Z, Manavis J, Helps S, Blumbergs PC · 2010
Researchers exposed mice to 900 MHz RF fields at 4 W/kg for 60 minutes or five days per week for 104 weeks. Control mice were sham-exposed or freely moving in cages, and positive controls received a stab wound. No increase in microglial Iba1 expression was found in exposed brains compared to controls, while positive controls showed substantial activation. Acute or two-year exposure did not produce microglial activation detectable by Iba1 immunostaining.