If so, what are the technology’s potential harmful effects?
It depends on what you consider long exposure, but I would say yes, there could very well be some potential harmful effects if you were to sit all day in front of an ultrahigh-frequency (UHF) RFID reader antenna emitting RF energy. In a previous post on this topic, in fact, I mentioned research conducted at the University of Texas at Arlington (see Can RFID Be Harmful to the Human Body?).
I reached out to the International Consortium on Non-Ionizing Radiation Protection (ICNIRP) to ask if the organization had carried out any research regarding RFID, but I did not receive a response. As a general guideline, people should remain at least 1 meter (3.3 feet) from a reader. That’s not to say you can’t come closer as you walk by such a device. You can—but if you are going to be exposed to the reader for any extended period of time, you should remain at least a meter away from the antennas.
Additionally, if a person is going to be in front of a reader, you should not turn it on and off to reduce his or her exposure, as some early-stage research indicates this could actually have an impact on pacemakers.
—Mark Roberti, Founder and Editor, RFID Journal