Radiation - Bluetooth & Cell/Cordless Phones
Cell Phone Radiation Science Review
Section 4: Radiation - Bluetooth, Wired Headsets & Cordless Phones
There is a great need for publicly available information on radiation emission levels associated with cell phones. This disclosure should be done at the point of sale.
A recent market study indicated that shoppers considered the SAR value of a phone important for their safety and a key element of their purchasing decision (Wiedemann 2008). Yet, as found in a 2006 survey by the German Federal Office for Radiation Protection, only 11% of respondents considered themselves well informed on the subject of cell phone radiation (BfS 2008c).
Using a headset is one of the simple, easy steps that consumers can take to decrease their exposure to cell phone radiation. Yet, which headset to use - wired or wireless? The research below discusses the latest science on the subject.
Bluetooth radiation emissions
According to findings and recommendations by government agencies and researchers in different countries, the use of Bluetooth headsets with cell phones decreases the overall levels of SAR exposure to the head (American Cancer Society 2008; BfS 2005; Martinez-Burdalo 2009; Swiss Federal Office of Public Health 2009a).
Bluetooth wireless technology is found in a diverse range of devices, such as cell phone headsets, car speakerphones and other automotive equipment, GPS, gaming equipment, computer accessories such as printers, keyboards, and mice, PDAs (personal digital assistants), personal media players, and medical, health, and wellness devices (CNET Reviews 2009; ICNIRP 2008; Morrow 2002). Bluetooth wireless technology allows radiofrequency devices to form connections for communicating one-on-one or for creating a personal wireless network within an approximately 30-feet-radius sphere. Bluetooth devices are used in a growing number of commercial and personal applications; the Bluetooth Specialist Interest Group, an industry trade association, lists over 6000 products that utilize Bluetooth technology (Bluetooth Special Interest Group 2009).
Bluetooth transmitters operate at frequency around 2.4 GHz. Bluetooth devices are assigned to one of three power classes: 1, 2 and 3. Class 2 transmitters – most commonly found in mobile devices – have a range of 30 feet (10 meters) and operate at 2.5 mW peak transmission power; class 3 devices are weaker than class 2, operating at peak transmission power of 1 mW in a range of less than 10 meters. Class 1 transmitters are the most powerful, with a range of 300 feet and peak transmission power of 100 mW. Class 1 Bluetooth devices can cause exposure to radiation similar to that emitted by a cell phone if they are operated in the immediate vicinity of the body. Bluetooth devices are designed to limit the radiation power exactly to that actually required. When the receiving device indicates that it is a few meters away, the transmitter immediately modifies its signal strength to suit the exact range, which reduces the total emitted radiation and signal interference (IT'IS 2005).
A study commissioned by the Swiss Federal Office of Public Health (FOPH) measured SAR for several Bluetooth devices, including two different class 3 hands-free cell phone headsets. The headsets tested had SAR values of 0.001 and 0.003 W/kg, which is 34 and 12 times lower than the SAR of the lowest-emission cell phone currently available (Swiss Federal Office of Public Health 2009a).
Of note, while the Bluetooth headset reduces radiation exposure to the head, transmission strength from the phone itself is not decreased. Bluetooth headset users frequently keep their phone in a pocket or clipped to the belt, a position that leads to radiation exposure of internal organs (Whittow 2008). As stated on the FCC website, “if the phone is mounted against the waist or other part of the body during use, then that part of the body will absorb RF energy” (FCC 2008). While the health effects of this exposure have not yet been assessed, the Swiss FOPH recommended that “cell phones should not be carried in a front trouser pocket when making calls” and that it may be safest “to hold the phone away from the body to reduce radiation exposure” (Swiss Federal Office of Public Health 2009a). Furthermore, a study from the Loughborough University (U.K.) reported that realistic everyday metallic objects found near the waistline, including a coin, a ring and a zipper increased the SAR in the body at different frequencies (Whittow 2008).
In the U.S., FCC certification of Bluetooth devices does not require measuring and reporting the SAR values. Bluetooth technology falls under the list of “low-power, non-licensed radiofrequency devices” that are classified in 47CFR Part 15 (FCC 1993, 2002). According to the FCC regulations, these unlicensed devices need to comply with the maxiumum permissible exposure limit. As stated by FCC:
"The FCC typically does not require RF exposure test data to be submitted with a filing to demonstrate compliance. Sometimes, applicants may choose to include such test data to expedite a filing. However, sufficient information should be included to satisfy the requirements of Section 15.247(b)(4), typically specific operating and installation instructions/requirements, warning/caution instructions and/or labels when applicable. If compliance cannot be ensured or determined based on the supporting information, (the operating configurations and exposure conditions of the host and final products that would operate with the Bluetooth transmitter module.) SAR or MPE evaluation may be requested as required by Section 1.1307(d)." (FCC 2007)
Wired (corded) hands-free headsets — radiation emissions
The use of corded earpieces/headsets is listed by the American Cancer Society as one of the easy ways to decrease SAR exposure to the head and brain during a cell phone conversation (American Cancer Society 2008).
With a corded headset, the voice signal is sent electronically to the earpiece directly from the phone in a similar manner as when standard headphones are plugged into a radio or a music player (Network & Academic Computing Services of University of California Irvine 2008). Depending on the position of a wired headset cable along the body, a certain proportion of the phone output radiofrequency radiation can be transmitted along the cable and elicit measurable SAR values in the torso and the head of the user (Kuhn 2008).
In the U.S., wired headsets are not regulated and their SAR values are generally not publicly available (Carnoy 2000). Several studies examined the issue of corded headsets safety, the potential for the headset/headset wire to act as a secondary antenna, and the effects of headset wire on radiation exposure to the torso (Carnoy 2000). One conclusion is clear: radiation exposure to the head is reduced with the use of a cordless headset, according to studies from the School of Electrical & Electronic Engineering at the Queen's University of Belfast (Troulis 2003) and the University of York Department of Electronics reached similar conclusions (Porter 2004) and Motorola (Bit-Babik 2003).
The Motorola study reported that, with a headset, SAR in the head is 8 times lower than when making calls holding the phone to the ear (Bit-Babik 2003). While this is a significant decrease, some degree of radiation exposure to the head occurs nevertheless (Bit-Babik 2003), which stands in contrast to statements from wired headset manufacturers that “SAR readings at the head are virtually zero when a corded mobile headset is used” (Plantronics 2005).
Unlike the earlier publications, a 2008 study carried out in the framework of the German research program on mobile telephones found that under a worst-case scenario for use of a GSM 1800 cell phone there was an increase in the SAR value in the inner ear (Kuhn 2008). It is possible that SAR exposure to the head when using a wired headset may be dependent on the cell phone transmission frequency and the type of transmission system, although researchers concluded that when a headset is used the overall exposure in the region of the head is reduced (Kuhn 2008).
Importantly, using a corded headset does not decrease the radiation output of the cell phone, which becomes absorbed into the torso instead of the head (FCC 2008). The Troulis (2003) study reported that for a waist-mounted cell phone, absorption of radiation by the body reduces the phone’s efficiency, thus increasing the required output power level. In this study, the peak 1 g SAR value was 0.450 W/kg for the phone itself, and with the hands-free wire connected, SAR increased to 1.14 W/kg. For a phone worn near the waist, this increased radiation would be absorbed into the body.
Scientific consensus has not yet been reached on whether corded or wireless headsets provide best radiation protection to the head and sensitive internal organs. Headset use has been recommended by government agencies in several countries as a way to reduce radiation exposure to the head (Switzerland, Germany, France, Israel, Austria, and the city of Toronto). According to the Swiss government, “As the brain is a sensitive organ, it is wise to use a hands-free kit (headset), since this reduces exposure of the head to radiation” (Swiss Federal Office of Public Health 2009a). Yet, which one is best?
Israel’s Ministry of Health urges cell phone users to rely on a wired, not wireless headset; the Swiss government recommends a wireless hands-free system (headphone or a headset) with a low power Bluetooth emitter; the Austrian government recommends using either a wired or a wireless headset; the German Federal Office for Radiation Protection and the city of Toronto’s department of Public Health simply recommend the use of headsets without stating which one is preferable. The UK Department of Health stated in a 2005 publication that the level of effectiveness of hands-free kits to reduce SAR is still uncertain (UK Department of Health 2005). Recent publication from the Swiss Foundation for Research on Information Technologies in Society (IT’IS) recommended for manufacturers to conduct tests of wired headsets’ SAR values to ensure that the phone-to-headset cable does not transmit radiofreqequency radiation towards the head and to the torso (Kuhn 2008).
While research on safer wireless technology is ongoing, one conclusion is clear: whether using either corded or Bluetooth headsets, it is reasonable to choose a phone with the lowest SAR value and to keep the cell phone away from the body during use.
Other common sources of radiofrequency radiation exposure
In addition to exposures from cell phones and Bluetooth devices, people are exposed to EMF radiation from a wide range of wireless devices at home and in the workplace, such as cordless home phones, baby monitors, and Wireless Local Area Networks (WLAN) (Frei 2009; Hillert 2006). Scientists at the Foundation for Research on Information Technologies in Society (IT’IS, Switzerland) reported an SAR value of 0.077 W/kg for baby monitor; 0.055 W/kg for cordless phone, and 0.81 W/kg for WLAN (IT'IS 2005). Additionally, IT'IS found that a class 1 Bluetooth USB plug-in antenna had an SAR of 0.466 W/kg, while a class 2 Bluetooth USB plug-in antenna had an SAR value of 0.0092 W/kg (Swiss Federal Office of Public Health 2009a). While research on this question is only beginning, a recent study from Spain suggested that cell phone exposures constitute the majority of radiofrequency exposure for an individual person, significantly exceeding exposure due to other wireless devices such as Bluetooth or WLAN (Martinez-Burdalo 2009).
Cordless telephones use the same type of radiofrequency radiation as cell phones. The main difference is that the cordless phone sends signal to the single base unit in the house while cell phones send signal to cell phone towers that can be located anywhere (CDC 2005). Several studies raised questions about the potential health impact of radiation from cordless home phones (Hardell, Carlberg 2006b; Hardell 2003; Mild 2007). A recently published study from Switzerland found that people who owned either a cordless phone or a mobile phone received more exposure to radio frequency radiation than those not owning either type of phone (Frei 2009).
While the cordless phone handset emits radiation only during a call (same as a cell phone), radiation emission from the cordless phone base station are continuous even when no calls are made (BfS 2008a). The German Federal Office of Radiation Protection recently issued a new requirement for cordless home phone models whereby base stations must be automatically switched off when not in use or when in standby mode (BfS 2008a). The Swiss government recommended keeping cordless phone base units away from relaxation places or work stations occupied for long periods as well as using a corded phone or a headset instead of a standard cordless phone (Swiss Federal Office of Public Health 2009b).
In the U.S., the types of cordless phones and the radiofrequency range they use have changed over the years. In early 1980s, cordless phones operated with frequency of 27 MHz (Phone Warehouse 2000). In late 1980s, FCC changed the cordless phone frequency band to 47-49 MHz (Code of Federal Regulations Chapter 47, section 15.233), followed by cordless phones that operated in 900 MHz range (cell phone frequency), 2.4 GHz (frequency band also used by Bluetooth and wireless LANs) and 5.8 GHz (Pedro 2006; teqFAQ 2009). The range of a cordless phone increased with each subsequent generation; 900 MHz phones have a range of 200 to 1500 feet, while 2.4 GHz and 5.8 GHz have a range of 300 to 2000 feet (Hanks 2004). New technologies such as DECT (Digital Enhanced Cordless Telecommunications) operate in 1900 MHz (cell phone) range (Rhein Tech 2006).
The International Commission on Non-Ionizing Radiation Protection (ICNIRP) recently recommended that public officials setting standards for EMF radiation exposure need to consider simultaneous exposure to radiation from multiple devices, such as cell phone, cordless home phone, Bluetooth, and WLAN, needs (ICNIRP 2008). Similarly, the Swiss and German governments have recommended precaution with respect to increasing exposure to radiofrequency devices (BfS 2008a). The Swiss government stated that "caution should be exercised primarily when using devices held close to the body, such as laptops, PDAs and Internet telephones” (Swiss Federal Office of Public Health 2009d). Clearly, this question needs to be resolved with a nation-wide study of the total EMF exposure people face on a daily basis.
Rapid growth in cell phone technology
Cell phone technology is constantly developing. Currently, GSM (Global System for Mobile Communication) is a standard protocol for digital mobile communication used for phone calls and transmission of text messages. Cell phones are also used for sending data or surfing the Internet. GPRS (General Packet Radio System) and Edge (Enhanced Data Rate for Global Evolution) are further developments of GSM that can transfer data at higher rates (sometimes called 2.5 Generation systems). The new (third) generation in mobile telecommunications includes W-CDMA (Code Division Multiple Access) and UMTS (Universal Mobile Telecommunication System), which have higher data transfer rate than GSM and are better suited to data and multimedia services while providing same level of cell phone and text messaging service. It is expected that in the near future, 3G technology will supersede the GSM standard (ICNIRP 2008; Swiss Federal Office of Public Health 2009c).
GSM protocol operates at frequencies of 900 and 1800 MHz; 900 MHz protocol has a peak output power of 2000 mW and maximum output power of 240 mW. 1800 MHz protocol operates with a peak output power of 1000 mW and maximum output power of 120 mW. 3G UMTS protocol operates at transmission frequency 2100 MHz, with both peak and maximum output power in the range of 125-250 mW.