Specific absorption rate (SAR) is defined as the power absorbed by unit mass of the tissue. There have been studies conducted regarding the SAR distribution of passive RFID systems operating at 125 kHz, 13.56 MHz and 900 MHz.
In 2009, Daniel W. Engels, then the director of the University of Texas at Arlington‘s Radio Frequency Innovation and Technology Center, and an associate professor in the college’s Department of Electrical Engineering, wrote a paper along with Darmindra D. Arumugam (then a student at the university), titled “Specific Absorption Rates in the Human Head and Shoulder for Passive UHF RFID Systems at 915 MHz.” Their research revealed that in an ideal absorption environment, an RFID reader located 10 centimeters (3.9 inches) from the human head presents a specific absorption rate above 1.6W/kg for both the spatial-peak 1 g and 10 g cube of tissue—the maximum value allowed by the U.S. Federal Communications Commission (FCC).
Researchers at the Austrian Institute of Technology studied the SAR distribution of low-frequency (LF) and high-frequency (HF) systems. Their results indicated that 125 kHz RFID solutions exceed recommended safety limits for absorption when the human body is exposed to a radiating antenna from a distance of 5 centimeters (2 inches) for even short periods of time. In case of 13.56 MHz systems, the study claimed, exposure for longer than six minutes could result in unsafe levels of absorption. The Austrian researchers found that a metallic implant “enhances the induced current densities and SAR inside the tissue” (see Computational Estimation of Personal Exposure Against Electromagnetic Fields Emitted by Typical RFID Applications at 125 kHz and 13.56 MHz).
There have been some reports that tumors have been discovered surrounding implants in laboratory rats. I don’t believe any definitive study has yet been performed to determine the health risks of human implants, though the U.S. Food and Drug Administration (FDA) has approved such implants for sale.
—Mark Roberti, Founder and Editor, RFID Journal
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