In IEEE and other standards-setting committees, there has been general agreement that behavioral disruption is the potentially adverse effect found in animals at the lowest exposure level. It is clearly a thermal effect. Independently developed standards have a similar basis. Obviously, it is important to limit exposure to small sources that might produce local injury even though the whole-body SAR does not exceed the standard. He said it corresponded to the smallest volume of tissue in which the exposure could be determined feasibly with methods available at the time.
Many cell phones operate near the limit, requiring careful measurements to determine compliance.
Unfortunately, SAR is impossible to measure inside the head. Complicated computer simulations or fluid-filled models are used instead. The limit was based on a thermal effect due to excessive total heat load in animals subject to whole-body exposure, the averaging requirement was based on engineering rather than toxicological considerations, and the methods of measurement are technically challenging.