The wireless technology known as Bluetooth is popular for connecting cell phones with cordless headsets. One reader, Nancy Ciaccia, is attracted to a slim and lightweight phone with Bluetooth connectivity, but worries that having a small radio transmitter planted next to her ear might be a health concern. "How long would a person have to use Bluetooth in order to have damage?" she writes. "If I am on it for two hours straight, what could that do?" And, on a more practical note, she asks how long a Bluetooth headset operates before it needs to be recharged.
First, though there has been a great deal of research, the evidence pointing to any health hazard from radiation in the 800 MHz to 2 GHz range at the power levels used by mobile phones is, at worst, equivocal. This suggests that if there is any risk at all, it is very small. Second, I have not seen any studies suggesting any risk from Bluetooth. This is not surprising. While a phone needs to transmit with enough power to reach a base station antenna that may be a couple of miles away, Bluetooth has a nominal range of 30 feet.
Because radio energy dissipates at a rate proportional to the square of the distance, the transmit power of a Bluetooth radio can be orders of magnitude lower than that of the phone itself. And except when you are actually using the headset for a conversation, the Bluetooth radio is idle nearly all the time.
This is done mainly to preserve battery life rather than because of health concerns, but while idle, the headset radio wakes up only for very brief spurts to let its partner in the phone know that it is still there and to check whether it is needed to take an incoming call (see BusinessWeek.com, 10/24/05, "Less Dashing to Find the Cell Phone").
As for standby and talk time, the battery life on Bluetooth headsets has improved greatly to the point where the charge on the headset lasts at least as long as that on the phone, and often longer. Also depending on the headset, there are a lot of charging options available. For example, a number of handset makers, including Motorola (MOT), Sony Ericsson, and Palm (PALM), offer Bluetooth headsets that can be recharged using the phone charger, eliminating one gadget to carry (see BusinessWeek.com, 6/28/06, "Motorola's Tin Ear").
Also, many Bluetooth headsets can be charged with a special USB cable plugged into a laptop. And Plantronics (PLT) offers the Discovery 645, a $170 headset that can recharge from a wall charger, a USB cable, or a AAA battery tucked away in its carrying case (see BusinessWeek.com, 7/25/06, "Hero of the High-Design Headset").