California officials issued the new report in response to increasing smartphone use in the United States, especially among children. About 95% of Americans own a cell phone, according to a press release from the California Department of Public Health, and the average age for a first cell phone is now 10 years old. About 12% of people use their smartphones for daily Internet access.
Over time, the number of cell phone calls per day, the length of each call, and the amount of time people use cell phones have increased. Because of changes in cell phone technology and increases in the number of base stations for transmitting wireless signals, the exposure from cell phone use—power output—has changed, mostly lowered, in many regions of the United States (1).