*SAR values are from tests conducted by Pong Research Corp on March 29, 2012 and submitted to the FCC on May 31, 2012. Because the SAR values were submitted to the FCC in graph form, EWG estimated numerical SAR values based on the chart available in WT Docket 11-186 (http://apps.fcc.gov/ecfs/document/view?id=7021921006). Pong’s filing to the FCC did not indicate whether SAR measurements were done at the head or in a body-worn configuration. In a personal communication, Pong informed EWG that the SAR measurements were done in a body-worn configuration, with the same distance from the test mannequin used by the phone manufacturer. Tests in the body-worn configuration were done at a 10 millimeter separation distance.

The study specifically used 2G and 3G frequencies — not the frequencies used on more advanced 4G or 5G networks. Researchers exposed the rodents’ entire bodies to the radiowaves for more than nine hours per day, for up to two years. (“A rat that is 2 years old is roughly equivalent to a 70-year-old person,” STAT News reports.) These exposure levels were much higher than what people would experience, John Bucher, senior scientist with the NTP, says in a statement. “So, these findings should not be directly extrapolated to human cell phone usage,” he says.

The frequency of radiofrequency electromagnetic radiation ranges from 30 kilohertz (30 kHz, or 30,000 Hz) to 300 gigahertz (300 GHz, or 300 billion Hz). Electromagnetic fields in the radiofrequency range are used for telecommunications applications, including cell phones, televisions, and radio transmissions. The human body absorbs energy from devices that emit radiofrequency electromagnetic radiation. The dose of the absorbed energy is estimated using a measure called the specific absorption rate (SAR), which is expressed in watts per kilogram of body weight.