Have any studies been conducted on this topic?
There's been some talk about whether RFID interferes with medical equipment (see Researchers Warn RFID May Disrupt Medical Equipment, New RFID Study Finds No Interference With Medical Devices, A Sobering Warning on RFID in Hospitals, Dutch RFID Interference Study Is a Worst-Case Test, Good and Bad News About RFID in Hospitals and Study Finds RFID Interferes With Medical Equipment). To my knowledge, however, there have not been any studies performed to examine the implications of long-term exposure to radio frequency identification on the human body.
RFID systems generally are low-power, and should not impact a person's health if a reader is operating within legal power output limits, and is kept at least 1 meter (3.3 feet) from the human body. That said, a company should never place an interrogator close enough to a worker that his or her head and eyes would be exposed to RF energy for long periods from close-range. What's more, if a reader activates and deactivate frequently, this could affect a pacemaker's functioning.
—Mark Roberti, Founder and Editor, RFID Journal