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
Del Vecchio G et al. · 2009
Italian scientists exposed brain cells to cell phone radiation for six days. The radiation alone didn't harm cells, but when combined with hydrogen peroxide, it increased damage to certain brain cells. This suggests cell phone radiation might amplify other sources of brain cell damage.
Del Vecchio G et al. · 2009
Researchers studied the effects of radiofrequency electromagnetic field exposure on neuronal maturation using two in vitro models: murine SN56 cholinergic cells and rat primary cortical neurons. Cells were exposed at 1 W/kg at 900 MHz GSM modulated, and neurite emission, outgrowth, and branching were examined at multiple time points. RF-EMF exposure reduced the number of neurites in both cell systems, and this reduction correlated with increased expression of beta-thymosin mRNA.
Del Vecchio G et al. · 2009
Söderqvist F, Carlberg M, Hansson Mild K, Hardell L · 2009
Researchers exposed 41 volunteers to a 30 min GSM 890 MHz signal at an average specific energy absorption rate distribution of 1.0 W/kg in the temporal area of the head. S100B showed no statistically significant increase, while transthyretin showed a statistically significant increase in the final blood sample 60 min after the end of the provocation compared to the sample taken immediately after provocation (p = 0.02). The researchers noted that the clinical significance of this finding, if any, is unknown.
Stovner LJ, Oftedal G, Straume A, Johnsson A. · 2008
The study aimed to investigate headache type and location in a provocation study to gain insight into possible causes and mechanisms. Seventeen participants completed 130 trials of sham or RF exposure. No significant difference existed in headache type, laterality, or location between the two exposure types. In most participants, the headache was compatible with tension-type headache.
Yao K, Wu W, Wang K, Ni S, Ye P, Yu Y, Ye J, Sun L. · 2008
Researchers exposed cultured human lens epithelial cells (HLECs) to a 1.8 GHz GSM radiofrequency field for 2 hours at specific absorption rates of 1, 2, 3, and 4 W/kg, then measured intracellular reactive oxygen species (ROS) and DNA damage. After exposure to 1.8 GHz RF for 2 h, HLECs exhibited significant intracellular ROS increase in the 2, 3, and 4 W/kg groups, and RF at 3 W/kg and 4 W/kg induced significant DNA damage consisting mainly of single strand breaks. When the radiofrequency field was superposed with 2 μT electromagnetic noise, the noise blocked the RF-induced ROS increase and DNA damage.
Johansson A et al. · 2008
Fifteen subjects with atopic dermatitis and 15 matched controls were exposed for 30 min to a 900 MHz GSM mobile phone-like RF field at 1 W/kg. Blood samples were taken before and after exposure to measure serum levels of substance P (SP), TNF R1, and brain derived neurotrophic factor (BDNF). At baseline, the atopic dermatitis group had significantly higher serum TNF R1 and significantly lower BDNF than controls, while SP did not differ. No effects of RF exposure were found on any of the measured substances. Symptom reports were too few to evaluate a possible correlation with exposure.
Buttiglione M et al. · 2007
Researchers exposed human neuroblastoma SH-SY5Y cells to 900 MHz radiofrequency radiation at 1 W/kg to study effects on gene expression and cell-cycle control. Short-term exposures produced a transient increase in Egr-1 mRNA levels along with activation of the MAPK subtypes ERK1/2 and SAPK/JNK. Exposure had an anti-proliferative effect, and a significant G2-M cell-cycle arrest was observed, with signs of apoptosis appearing after 24 hours. A significant decrease in mRNA levels of Bcl-2 and survivin genes, both linked to signaling between G2-M arrest and apoptosis, was also observed.
Sun LX, Yao K, He JL, Lu DQ, Wang KJ, Li HW · 2006
Chinese researchers exposed human eye lens cells to mobile phone radiation (1.8 GHz) at different power levels for 2 hours to see if it damaged DNA. They found that lower exposure levels (1-3 W/kg SAR) caused either no DNA damage or damage that the cells could repair within an hour, but the highest level (4 W/kg SAR) caused permanent DNA damage that cells couldn't fix.
Lixia S et al. · 2006
Researchers exposed human eye lens cells to cell phone radiation at different power levels for 2 hours. Higher exposures caused temporary DNA damage and triggered cellular stress responses, suggesting that phone radiation can affect eye cells even without heating tissue.
Stronati L et al. · 2006
Italian and British researchers exposed human immune cells (lymphocytes) to 935 MHz cell phone radiation for 24 hours at levels similar to what tissues experience during phone use. Using multiple DNA damage tests, they found no genetic damage from the radiation alone, and the radiation didn't make X-ray damage worse. This suggests that 24-hour exposure to this type of cell phone radiation doesn't directly break DNA or interfere with DNA repair.
Sun LX, Yao K, Jiang H, He JL, Lu DQ, Wang KJ, Li HW · 2006
Researchers exposed cultured human lens epithelial cells to 217 Hz modulated microwave radiation at four SAR levels for 2 hours. DNA single strand breaks were measured using the comet assay immediately after irradiation and at 30 and 60 minutes afterward. At the highest dose, significant DNA damage remained one hour after irradiation and cell proliferation was significantly decreased.
Paulraj R, Behari J. · 2006
Researchers exposed 35-day-old male Wistar rats to microwave radiation at 2.45 GHz and 16.5 GHz for 35 days to study effects on developing rat brain. After exposure, the researchers measured DNA single strand breaks in brain tissue using micro gel electrophoresis (comet assay), with fifty cells from each slide and two slides per animal observed. The study found a statistically significant increase (p < 0.001) in DNA single strand breaks in the brain cells of exposed rats.
Paulraj R, Behari J. · 2006
Researchers exposed developing rat brains to microwave radiation at frequencies used in WiFi (2.45 GHz) and other wireless devices (16.5 GHz) for 35 days. They found statistically significant increases in DNA single strand breaks in brain cells compared to unexposed rats. This suggests that chronic microwave exposure during brain development may cause genetic damage that could potentially lead to long-term health problems.
Chauhan V et al. · 2006
Researchers exposed HL-60 and MM6 cells to intermittent 1.9 GHz pulse-modulated RF fields at SARs of 1 and 10 W/kg for 6 hours. No significant changes in gene expression were found between sham-exposed and RF-exposed groups in either cell line. Positive heat-shock controls showed significant increases in HSP27, HSP70, c-fos, and c-jun at both time points.
Wilen J, Johansson A, Kalezic N, Lyskov E, Sandstrom M · 2006
Researchers investigated the effect of a mobile phone-like radiofrequency electromagnetic field on people who reported subjective symptoms when using mobile phones. Twenty subjects with mobile phone-related symptoms were matched with 20 controls without such symptoms, and each person took part in one true exposure session and one sham exposure session in random order. No significant differences related to radiofrequency exposure conditions were detected. The symptomatic group displayed a shift in low/high frequency ratio towards sympathetic dominance in the autonomous nervous system during tests, regardless of exposure condition.
Paulraj R, Behari J · 2006
Researchers exposed developing rat brains to microwave radiation at frequencies commonly used in WiFi and radar systems (2.45 and 16.5 GHz) for 35 days. They found statistically significant DNA damage in brain cells, specifically single-strand breaks that can interfere with normal cellular function. This suggests that chronic exposure to low-level microwave radiation during brain development may cause genetic damage.
Tuschl H, Novak W, Molla-Djafari H. · 2006
The study assessed whether GSM-modulated RF fields have adverse effects on the functional competence of human immune cells. Exposure was performed at GSM Basic 1950 MHz with an SAR of 1 mW/g in an intermittent mode of 5 minutes on and 10 minutes off for 8 hours. Researchers evaluated intracellular cytokine production, immune-relevant gene activity, and cytotoxicity of lymphokine-activated killer cells using blood from at least 15 donors per parameter. No statistically significant effects of exposure were found.
Stronati L et al. · 2006
The study used alkaline comet assay, metaphase analysis, micronucleus test, and nuclear division index to assess DNA strand breaks, chromosomal aberrations, sister chromatid exchanges, micronuclei, and cell cycling speed. It comprehensively examined whether 24-hour continuous exposure to a 935 MHz GSM signal at 1 or 2 W/kg is genotoxic per se or can influence x-ray genotoxicity. Within the experimental parameters, no effect from the RFR signal was observed in any instance. The SAR values chosen were near the upper limit of energy absorption in localized tissue during cellular telephone use.
Wilen J, Johansson A, Kalezic N, Lyskov E, Sandstrom M. · 2006
Swedish researchers exposed 20 people who experience symptoms from mobile phones and 20 people without symptoms to 900 MHz cell phone radiation for 30 minutes at levels typical of phone use. While the radiation didn't cause immediate measurable changes in either group, the symptomatic individuals showed different nervous system patterns during cognitive tests, suggesting their autonomic nervous systems may function differently regardless of radiation exposure.
Lixia S et al. · 2006
Researchers exposed human lens epithelial cells (hLEC) to a 1.8 GHz GSM radiofrequency field at SARs of 1, 2, and 3 W/kg for 2 hours and then measured DNA damage, Hsp70 expression, and cell proliferation. DNA breaks at 1 and 2 W/kg were not significantly different from controls at any time point, while the 3 W/kg dose showed significantly increased DNA damage only at 0 and 30 minutes after exposure. Hsp70 protein expression was significantly increased at 2 and 3 W/kg, but Hsp70 mRNA expression did not change in any group, and cell proliferation was unaffected at all doses.
Scarfi MR et al. · 2006
Researchers exposed human peripheral blood lymphocytes from 10 healthy donors to 900 MHz GSM signals at SARs of 0, 1, 5, and 10 W/kg for 24 hours. The cytokinesis-block micronucleus assay showed no genotoxic or cytotoxic effects across the range of SARs investigated. Two independent laboratories (ENEA Rome and CNR-IREA Naples) each tested five donors and cross-scored slides, confirming the findings.
Sun LX, Yao K, He JL, Lu DQ, Wang KJ, Li HW. · 2006
Researchers exposed human eye lens cells to cell phone radiation for 2 hours at different power levels. Lower levels caused repairable DNA damage, but higher power (4 W/kg) caused permanent breaks cells couldn't fix, suggesting a threshold where radiation overwhelms natural repair.
Sun LX, Yao K, He JL, Lu DQ, Wang KJ, Li HW. · 2006
Cultured LECs were exposed to 217 Hz modulated 1.8 GHz microwave radiation at specific absorption rates of 0, 1, 2, 3, and 4 W/kg for 2 hours. DNA single strand breaks were detected with comet assay at 0, 30, 60, 120, and 240 minutes after irradiation. At 1 and 2 W/kg, the difference in DNA breaks between exposure and sham exposure groups was not significant at any detection time. At 3 and 4 W/kg, differences were significant immediately and 30 minutes after irradiation, with the difference disappearing after one hour in the 3 W/kg group but persisting in the 4 W/kg group.
Chauhan V et al. · 2006
Researchers exposed human lymphoblastoma TK6 cells to 1.9 GHz pulse-modulated RF fields at SARs of 1 and 10 W/kg. They assessed expression of proto-oncogenes FOS, JUN, and MYC using real-time RT-PCR. They also monitored transcript levels of the heat-shock proteins HSP27 and inducible HSP70. Transcript levels in RF-exposed cells showed no significant difference compared to sham-exposed cells. Positive heat-shock controls showed significant elevation of HSP27, HSP70, FOS, and JUN, and a decline in MYC mRNA.