A cellular telephone user's level of exposure to RF energy depends on several factors, including:• The number and duration of calls.
• The amount of cellular telephone traffic at a given time.
• The distance from the nearest cellular base station.
• The quality of the cellular transmission.
• The size of the handset.
• How far the antenna is extended.
• Whether or not a hands-free device is used.
This answer is based on source information from the National Cancer Institute.