An article by columnist Mark Scherer entitled “Cell-Phone Safety: What the FCC Didn’t Test” is in this week’s Time magazine. It points out
“FCC testing regulations notably chose not to simulate a situation in which the phone was broadcasting at full power while inside a shirt or pants pocket flush against the body, an odd oversight given the known habits of many cellular-phone users. As a matter of physics, radio-frequency energy generally increases sharply as distance is reduced. “The exposure is definitely related to distance,” says (retired FCC RF safety expert Robert) Cleveland.”
The article is referring to the provisions in the somewhat obscure, but key for RF safety issues in cell phones, OET Bulletin 64, Supplement C (“OETB65C”). This publication is not codified in the FCC rules and was last revised in January 2001, almost a decade ago. Whether or not the content of this publication made sense when it was adopted in 2001, a lot has changed since then in the use of the covered devices and new devices like my beloved IPod Touch, essentially a PDA with Wi-Fi, have become common.
The provisions Mr. Scherer was writing about are on p. 41-2 of OETB65C. They say:
“Body-worn operating configurations should be tested with the belt-clips and holsters attached to the device and positioned against a flat phantom in normal use configurations. … Both the physical spacing to the body of the user as dictated by the accessory and the materials used in an accessory affect the SAR produced by the transmitting device. …Body-worn accessories may not always be supplied or available as options for some devices that are intended to be authorized for body-worn use. A separation distance of 1.5 cm between the back of the device and a flat phantom is recommended for testing body-worn SAR compliance under such circumstances. Other separation distances may be used, but they should not exceed 2.5 cm.”
The “phantom” referred to above is a dummy that has the electromagnetic properties of a human body. It is often a body-shaped container of a special liquid. The cell phone or other device is placed next to the container, as it would be not to the body in actual use, and a probe is moved around in the liquid to measure the resulting radio field. With knowledge of the electromagnetic properties of the body/liquid, one can then compute SAR – essentially how much heat is being induced in the body at a given point.
The above quote from OETB65C essentially allows the device manufacturer to assume a distance from the body of 1.5-2.4 cm (0.59-0.98 inches) even if they do not provide any holder that keeps it that far from the body. Mr. Scherer describes this as “an odd oversight given the known habits of many cellular-phone users.” Indeed, don’t a lot of people carry cell phones, Blackberries, and iPhones in their pockets? In view of the FCC’s recent interest to help inform the public about SAR by writing a whole consumer fact sheet entitled “SAR For Cell Phones: What It Means For You”, isn’t it odd that this is is never mentioned therein?
So suggestions for FCC to think about in this area:
- Maybe OETB65C, and the other parts of the OETB65 series, should be revised at least once a decade?
- Maybe the FCC/CGB fact sheet recently issued to explain SAR should also point out that the SAR measured to be in compliance with FCC rules is not meaningful unless the consumer actually uses the phone with the body separation that was assumed.
- As previously stated in my personal blog, maybe the FCC/CGB fact sheet should also point out that Blackberries/iPhones used in the “typing” mode are subject to a higher SAR limit of 4.0 W/kg so that there is a significant safety margin when they are used in this mode. SAR measurements in this mode are not normally made available to the public in a convenient form.
- FCC/CGB and CTIA might want to think about making more pragmatic information available about decreasing exposure from cell phones – it isn’t proven harmful, but it certainly isn’t doing you any good. They might want to consider material from an RF safety site an RF safety site operated not by a radical environmental group, but by AFOM – the French counterpart of CTIA. This site out simply and clearly states (in French) that cell phones operate at maximum power, hence maximum SAR, in areas with weak signals and that health authorities suggest using your phone in strong signal areas preferentially.