Jump up ^ "Téléphones mobiles : santé et sécurité" (in French). Le ministère de la santé, de la jeunesse et des sports. 2 January 2008. Retrieved 19 January 2008. Lay article in (in English) making comment at Gitlin, Jonathan M. (3 January 2008). "France: Beware excessive cell phone use?: despite lack of data". Ars Technica. Retrieved 19 January 2008.
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).